Gasoline questions/debate

[MotiveLensPhoto]

Recently my go-to for ethanol free gas stopped carrying it.

Choice 2 is the airport 15 miles away, where I'm required to bring a 5 gallon can that they fill up. Not ideal.

Drive 27 miles for the next closest station (according to puregas.org), which seems even more pointless.

 

High octane (99 and 101) unleaded E10 is readily available near me.

 

Is it better to run a higher octane unleaded with no additives?

 

Use a lead additive?

 

Stabilizer?

 

How often?

 

1973 Riviera

 

 

[greenie]

27 miles seems like a great excuse to get the Riv out for a drive. Even the ethanol free fuel gets stale quickly, so a 54 mile roundtrip to fill the tank seems worthwhile. In south central PA and northern MD, my choices are a 10 mile trip or a 25 miler. The latter is a bit cheaper, I think 3.49/gal for 89 the last time. Hopefully this won’t start a debate about lead and valve seats. I would use stabilizer for the long winters. When the time comes to refresh the heads, by all means spring for the hardened valve seats.

[Pfeil]

6 hours ago, Golden73 said:

Recently my go-to for ethanol free gas stopped carrying it.

Choice 2 is the airport 15 miles away, where I'm required to bring a 5 gallon can that they fill up. Not ideal.

Drive 27 miles for the next closest station (according to puregas.org), which seems even more pointless.

 

High octane (99 and 101) unleaded E10 is readily available near me.

 

Is it better to run a higher octane unleaded with no additives?

 

Use a lead additive?

 

Stabilizer?

 

How often?

 

1973 Riviera

 

 

 

 

Rule out choice 2 if you are talking about running 100LL. It's illegal to use in a car on a public road. That also goes for adding lead-if you could even find it to buy.

[TerryB]

56 minutes ago, Pfeil said:

 

 

Rule out choice 2 if you are talking about running 100LL. It's illegal to use in a car on a public road. That also goes for adding lead-if you could even find it to buy.

Is that due to it not being taxed for road use?

[Pfeil]

7 minutes ago, TerryB said:

Is that due to it not being taxed for road use?

Twofold, it's not taxed for road use, but the most concern is lead being released into the atmosphere by the consumption of the fuel. Besides on 1975 and newer cars the lead contaminates their catalytic converters. 

[Matt Harwood]

I've found that keeping the gas moving through the car is more important than the type of gas. Ethanol can be a problem but it typically becomes a problem after prolonged sitting (cue the anecdotes about how someone put ethanol in his tank and his engine exploded and then dogs and cats started living together). If you drive regularly it should not be an issue. Most modern carb rebuild kits, fuel pumps, and hoses are ethanol resistant. There are surely a few issues regarding its lower H_vap and "vapor lock" and sometimes reduced energy content, but those issues can be addressed and should not be an issue in a 1973 car in good mechanical health.

 

I have had thousands of cars pass through my hands, some sitting for weeks or months, not counting my personal cars that sit from November to April, and I have never, ever gone out and found special gas or added anything to gas tanks to boost octane or help store the gas, and I have never had a fuel-related problem. The closest we've ever come to having fuel-related problems is running out of gas and in one case, the gas sitting in the tank acted like a solvent and removed whatever home-made coating the previous owner had used to seal the tank (it was some kind of tar-based substance). 

 

I think the scary stories of ethanol far outstrip the reality and I'm not sure I'd spend a lot of extra time chasing special gasoline. By 1973, compression ratios were down enough that today's high octane pump gas will keep it perfectly happy. 

 

The best thing you can do for your car? Drive it. The more you do that, the less the gas in the tank will matter.

[edinmass]

To a certain extent I would agree with Matt. Keeping fresh fuel in the car and consuming it is the best option, cars built before the war have a much harder time with E10, as the carburetors are not nearly as adjustable and vapor lock becomes a common problem. 

[carbking]

13 hours ago, Golden73 said:

Recently my go-to for ethanol free gas stopped carrying it.

Choice 2 is the airport 15 miles away, where I'm required to bring a 5 gallon can that they fill up. Not ideal.

Drive 27 miles for the next closest station (according to puregas.org), which seems even more pointless.

 

High octane (99 and 101) unleaded E10 is readily available near me.

 

Is it better to run a higher octane unleaded with no additives?

 

Use a lead additive?

 

Stabilizer?

 

How often?

 

1973 Riviera

 

 

 

"High octane (99 and 101) unleaded E10 is readily available near me."

 

If this is U.S. octane, way too high for a '73 Riv. If Canadian octane, do a search on RON, MON, and AKI.

 

I'm with Matt on driving more, and keeping fresh fuel in the carburetor. If one will start one's vehicle once a week, and move it at least twice the circumference of a tire, one will have far fewer service issues.

 

I don't agree that non-leather accelerator pumps are ethanol-resistant UNLESS one does drive sufficiently often to always keep fuel in the carb. If allowed to dry out, they tend to become brittle, and crack (fail) with use.

 

And modern floats can be a problem. A used 50 year-old original that tests good (opinion) is superior to the foam floats, and especially the brass floats made on the other side of the world. Ethanol eats the material they use to replace solder.

 

Jon.

[vermontboy]

Nothing new

 

 

[zepher]

But today's ethanol can be hard on older rubber fuel lines and fuel pump parts.

 

Why risk a fire when you can easily replace all of your rubber fuel lines and seals with modern, ethanol resistant stuff?

[John_S_in_Penna]

18 hours ago, vermontboy said:

Nothing new

 

Even though ethanol has been tried before, 

as the old picture shows, was it successful?

Did it cause difficulty even then?  We may not

know, unless we can find decades-old accounts

from those early years.  In previous generations,

most recently the 1970's energy crisis, it certainly

didn't stay around and become a successful alternative

to full-strength gasoline.

Edited July 15, 2020 by John_S_in_Penna (see edit history)

[72caddy]

I see that you are around Chicago. Any marina should have non ethanol gas. Probably only 91 octane to boot. Surprised that your 1973 Riv isn't already compatible with 'unleaded'. My 1972 Cadillac is and runs fine with todays gas.

Edited July 15, 2020 by 72caddy (see edit history)

[padgett]

I found a very good description here. Knew about Kettering and Midgley from my days at GMI and remembered that: " On the list of antiknock fuels, pure ethyl alcohol was most effective"  but TET was more cost effective.

[MotiveLensPhoto]

I meant 91+ octane, not 99.

 

The mechanics I talked to (speed shops, restorers, etc.), all said that ethanol free is best for the carbs, and highest octane is second choice. You're mostly saying the opposite - ethanol doesn't matter. 

 

And yes, I do drive it. 50 - 100 miles a week in the summer, and sta-bil on a full tank when it gets stored for the winter.

 

 

[padgett]

The major difference between leaded and unleaded cars were hardened exhaust valve seats. GM began dropping compression and going to hardened seats in 1971 and was across the board by '73 when EGR came in.

 

ps octane just relates to how fast a fuel burns and really has nothing to do with the energy in a gallon. Ethanol comes from a variety of sources of which corn is the least efficient. It has much lower energy/gal than gasoline so needs richer jets/more pulse width and gets less MPG.

[Marty Roth]

56 minutes ago, Golden73 said:

I meant 91+ octane, not 99.

 

The mechanics I talked to (speed shops, restorers, etc.), all said that ethanol free is best for the carbs, and highest octane is second choice. You're mostly saying the opposite - ethanol doesn't matter. 

 

And yes, I do drive it. 50 - 100 miles a week in the summer, and sta-bil on a full tank when it gets stored for the winter.

 

 

 

Higher octane, according to several folks who live with Vapor Lock issues, is not the solution.

 

Driving in summer heat, and higher temps, with, and without altitude issues, I've learned that "LOWERING" the octane rating helps to stave off vapor lock. During the Oklahoma City Glidden Tour with temps in the 100 degree range, I used the lowest octanes available (86 or 87), sometimes with, sometimes without ethanol and also always added 10% to 20% diesel - all this while driving our unrestored 1941 Cadillac with the original (never opened) FLATHEAD V8, an engine type known to suffer vapor lock. Several friends advised that they felt we needed an engine rebuild because of the amount of blue smoke from the tailpipe, until I explained the reason. We may have assisted Oklahoma in controlling mosquitoes during that week. 

 

The benefit? - through the entire week we never even once had to supplement the fuel system with turning on the supplemental electric - Absolutely NO Vapor Lock in 100 degree heat in OK City in September in a car which has ongoing regular vapor lock issues. Did it hurt the car to add diesel to the fuel? I sincerely doubt it ! We have since driven the '41 another 15,xxx miles, a few thousand of it on interstate highways and keeping up with (reasonable) traffic.

 

It runs better all the time, and we drive it anywhere and everywhere - Maine to Montana, Mount Washington, New Hampshire to Pikes Peak Colorado, Florida Keys to San Diego, Prince Edward Island, Canada to Cadillac Mountain in Acadia National Park to Big Bend National Park in Texas to Sault Ste Marie, Michigan and Canada - Wyoming, Colorado, New Mexico, Arizona - Logan, Utah to Virginia Beach - Giddy-up-Go!

 

Edited July 17, 2020 by Marty Roth
typo, and additional note (see edit history)

[C Carl]

Very cool, Marty ! Please tell us something about the picture with the two ancient locomotives seemingly out in a remote location.    -    Carl 

[JamesR]

I'll still use alcohol-free gas because I feel so privileged to live in an area where it's plentiful, when so many other places don't have any stations that sell it. For me, not buying alcohol-free gas would be like living in Maine and never eating lobster. 😄 Most of my old cars have had new fuel pumps and carb rebuilds since I've owned them, so I guess it doesn't really matter.

[carbking]

On 7/16/2020 at 5:58 PM, Golden73 said:

I meant 91+ octane, not 99.

 

The mechanics I talked to (speed shops, restorers, etc.), all said that ethanol free is best for the carbs, and highest octane is second choice. You're mostly saying the opposite - ethanol doesn't matter. 

 

And yes, I do drive it. 50 - 100 miles a week in the summer, and sta-bil on a full tank when it gets stored for the winter.

 

 

Ethanol and higher octane BOTH matter, to a certain extent.

 

Ethanol has less energy than gasoline, so might require carburetor recalibration. It DOES effect non-leather accelerator pumps, as well as soft fuel lines in vehicles not frequently driven. Over a long time (25~30 years or so), it can cause damage to aluminum or zinc alloy carburetor bodies. Repeat, this is a LONG-TERM effect.

 

Too high octane fuel will not completely burn in an engine designed for lower octane, without timing and possibly (depending on the compression ration) compression changes.

 

So, if your engine is not specifically designed for the higher octane; you get worse performance, lower fuel economy, and pay more at the pump for the privilege of lowering your performance!

 

Jon.

[PFitz]

On ‎7‎/‎16‎/‎2020 at 7:54 PM, Marty Roth said:

 

Higher octane, according to several folks who live with Vapor Lock issues, is not the solution.

 

Driving in summer heat, and higher temps, with, and without altitude issues, I've learned that "LOWERING" the octane rating helps to stave off vapor lock. During the Oklahoma City Glidden Tour with temps in the 100 degree range, I used the lowest octanes available (86 or 87), sometimes with, sometimes without ethanol and also always added 10% to 20% diesel - all this while driving our unrestored 1941 Cadillac with the original (never opened) FLATHEAD V8, an engine type known to suffer vapor lock. Several friends advised that they felt we needed an engine rebuild because of the amount of blue smoke from the tailpipe, until I explained the reason. We may have assisted Oklahoma in controlling mosquitoes during that week. 

 

The benefit? - through the entire week we never even once had to supplement the fuel system with turning on the supplemental electric - Absolutely NO Vapor Lock in 100 degree heat in OK City in September in a car which has ongoing regular vapor lock issues. Did it hurt the car to add diesel to the fuel? I sincerely doubt it ! We have since driven the '41 another 15,xxx miles, a few thousand of it on interstate highways and keeping up with (reasonable) traffic.

 

It runs better all the time, and we drive it anywhere and everywhere - Maine to Montana, Mount Washington, New Hampshire to Pikes Peak Colorado, Florida Keys to San Diego, Prince Edward Island, Canada to Cadillac Mountain in Acadia National Park to Big Bend National Park in Texas to Sault Ste Marie, Michigan and Canada - Wyoming, Colorado, New Mexico, Arizona - Logan, Utah to Virginia Beach - Giddy-up-Go!

 

 

A late Friend was an engineer at Sun Oil Co (Sunoco) for many years. His work at Sunoco was as advisor to Rochester Carburetor division helping them design carbs with the fuels Sunoco was developing. He also owned and drove antiques. He was another that said that to help reduce chances of vapor lock, add 10% diesel to the gasoline to lower the vapor pressure. He also said, don't go over 10% because it makes the engine put out more heat and that will add to the problem.

 

Paul

[Buick35]

Kind of off the subject but about 10 years ago I bought an 82 Mercedes diesel that I converted to run on vegetable oil.People behind me said it smelled like fren ch fries and gave them the munchies. I probably should have kept that car.Greg.

[MotiveLensPhoto]

On 7/15/2020 at 4:55 PM, 72caddy said:

I see that you are around Chicago. Any marina should have non ethanol gas. Probably only 91 octane to boot. Surprised that your 1973 Riv isn't already compatible with 'unleaded'. My 1972 Cadillac is and runs fine with todays gas.

 

There are a couple marinas nearby. I used to go to Sandwich, IL but they stopped carrying because of limited availability. Lake Holiday you can't drive to the pump. The Joliet airport (according to Puregas) sells it but I've never been and the whole thing seems rather complicated. You have to bring a 5gal can and have someone else run to the pump.

 

My car does run well on 93 octane but the whole issue is (I'm told) that ethanol damages the carburator over time.

[carbking]

1 hour ago, Golden73 said:

 

There are a couple marinas nearby. I used to go to Sandwich, IL but they stopped carrying because of limited availability. Lake Holiday you can't drive to the pump. The Joliet airport (according to Puregas) sells it but I've never been and the whole thing seems rather complicated. You have to bring a 5gal can and have someone else run to the pump.

 

My car does run well on 93 octane but the whole issue is (I'm told) that ethanol damages the carburator over time.

 

If you are truly concerned about the long time damage:

 

These are NOT rare carburetors, as the Riv used the same carb as other 455's (7043240).

 

Pick up one (or more), rebuild it/them (I happen to know of an excellent source for ethanol-friendly rebuild kits  ),  and put them on the shelf for the future.

 

Change the soft fuel hose(s) every five years.

 

Drive and enjoy the vehicle.

 

Jon.

[padgett]

Must admit that has been part of my philosophy for a long time. The only issue is that different QJs have different inlets, some straight, others side, some with internal filters, others without. I keep my original '70 RA carb in a big baggie and also have a separate block with the correct date code.

[Guest]

4 hours ago, PFitz said:

He was another that said that to help reduce chances of vapor lock, add 10% diesel to the gasoline to lower the vapor pressure. He also said, don't go over 10% because it makes the engine put out more heat and that will add to the problem.

This works really well as does Kerosene but it is more expensive.  I also found that using a 195 thermostat made my engine run better on current gasoline.

[padgett]

Interesting, thought Pontiacs always used 195s at least back to 1957. I run 180F in Computer cars and 160F in non. Helps to keep underhood temps down. For me keeping the fuel lines away from the block/headers eliminated vapor lock but my AC cars always had a return line & usually larger radiators. My real difficulty was preventing hot soak of the starter.

[Guest]

padgett

My Pontiac is the one in my avatar.  1930 Custom Sedan it came with a 160, when I started driving it in 1959 I went to a 180 for the winter and then tried a 190 and a few years later went to a 195 year round.

[Dynaflash8]

On 7/12/2020 at 3:27 PM, Pfeil said:

 

 

Rule out choice 2 if you are talking about running 100LL. It's illegal to use in a car on a public road. That also goes for adding lead-if you could even find it to buy.

#2 how're they going to catch you?  Our ethanol free gas is 8miles away. He is old and the station has been for sale for a long time.  When he shuts down, I guess I'll have to stop trying to drive my '39 Buick when Florida temps are over 87/88 (which is all the time in the summer) unless I go to the electric fuel pump full time. My '39 never ever vapor locked in over 40 years ownership (it gets well over 90 in both Maryland and Virginia from time to time in summer) until I moved to Florida and couldn't find non-ethanol at first.  I found it would vapor lock driving 50 miles an hour down the highway.  Always too, if I stopped for gas, it would start right back up, go 100 feet, and quit.  An electric fuel pump on a toggle switch is the only alternative when it does that.  It's very annoying.  With non-ethanol it doesn't do that.  In the upper 90s here, it rarely might, occasionally.  With ethanol it is immediately.  That makes touring hard because typically non-ethanol is not available.  On the '39 the steel gas line is snapped into a clip attached to the cylinder head between the head and the thermostat housing.  That doesn't help.  I have wrapped the steel line in that foam rubber stuff they sell at Home Depot to keep home water heat pipes from freezing up north.  That has helped some.  Here in Florida, thanks to former Governor Crist, it is nearly impossible to find non-ethanol.  It's outlawed unless the station has low volume like the one in downtown Sebring, which sells only non-ethanol.  I hate the stuff.  The '91 Park Avenue seems to do okay on ethanol.  The '41 Roadmaster is still out on the question.  I do not believe frequent driving has a thing to do with it, unless you run ethanol all the time.  I try never to put it in my two pre-War Buicks except on distant tours.

Edited July 18, 2020 by Dynaflash8 (see edit history)

[keithb7]

My latest thoughts on ethanol free fuel:

 

 

[MotiveLensPhoto]

21 hours ago, carbking said:

 

Pick up one (or more), rebuild it/them (I happen to know of an excellent source for ethanol-friendly rebuild kits  ),  and put them on the shelf for the future.

 

Change the soft fuel hose(s) every five years.

 

Drive and enjoy the vehicle.

 

Jon.

Rebuilding or installing a new carb is not in my skill set, sadly. Fortunately, I found a good mechanic that really likes working on my car for some reason so he treats me well.

[carbking]

Dynaflash - if you stop for gas (or any time you restart the engine when the engine is hot), run the engine at a fast idle (1500~1800 RPM) for 30~45 seconds BEFORE you put it in gear. You are experiencing "hot soak". Once you clear the fumes in the air cleaner, and the puddles in the intake manifold, the engine should run as it did before you shut it off.

 

Jon.

[W_Higgins]

1 hour ago, carbking said:

Dynaflash - if you stop for gas (or any time you restart the engine when the engine is hot), run the engine at a fast idle (1500~1800 RPM) for 30~45 seconds BEFORE you put it in gear. You are experiencing "hot soak". Once you clear the fumes in the air cleaner, and the puddles in the intake manifold, the engine should run as it did before you shut it off.

 

Jon.

 

Jon, I'm interested to hear your take on mixing diesel with gasoline as was mentioned above.  Do you care to comment?

 

 

[padgett]

Heard of it, think was in a Clive Cussler novel, but thought mixing diesel or kersosine with gasoline was to stretch scarce or rationed gasoline supplies.

[PFitz]

23 hours ago, Tinindian said:

This works really well as does Kerosene but it is more expensive.  I also found that using a 195 thermostat made my engine run better on current gasoline.

 For just a couple dollars difference on two gallons out of a 20 gallon tank, I'd prefer to pay that to avoid being stuck on the side of the road, on a hot day, hood open, and waiting for the fuel system to cool down.

 

Been there,..... all too often. And they weren't even my cars.

 

Paul

Edited July 19, 2020 by PFitz (see edit history)

[Matt Harwood]

I'm not sure that adding diesel to gasoline is any more effective than the other anecdotal evidence like, say, putting clothes pins on the fuel line. Diesel fuel is extremely LOW octane and while its H_vap might be slightly higher I'm not sure that 10% would make the difference between vapor and liquid on a hot day.

 

There's no question that ethanol gas (in fact, all fuels today) vaporizes at much lower temperatures than the fuels of the past, and that's the problem. It's entirely due to the use of high-pressure fuel injection and sealed fuel system. There's just no need to worry about it anymore, it's a non-issue for modern cars, consumers, and fuel suppliers. It's a problem on old cars when they get hot, but it's definitely a solvable problem.

 

I own two of the very worst offenders in terms of "vapor lock" issues, a 1929 Cadillac where the Johnson UPDRAFT carburetor hangs between the exhaust manifolds under a metal cover, and a Lincoln K where the carburetor not only sits between the exhaust manifolds, but is actually attached to them. Both cars gave me fits with fuel vaporization issues but I solved them and both cars run properly (well, the Lincoln ran properly until I took it apart again) on modern gas without any extreme measures or special chemistry in the fuel. My Cadillac has not run in maybe 9 months, but I will wager I can go out there right now and have it running in 10 seconds. The fuel is a problem, but a solvable one that doesn't require avgas, diesel fuel, boat gas, additives, lead, Windex, kerosene, paint thinner, or anything else beyond dumping the cheapest, crappiest gas you can find in the tank. 

 

Yes, an electric fuel pump is a big part of the equation, but it's a mistake to look at it as a crutch any more than a light bulb is a crutch for generating light relative to a candle. I've driven my Cadillac 200 miles at 50 MPH on a 104 degree day and yes, I could hear the fuel boiling in the carburetor when we stopped and it was a little fussy right at the end of the trip, but it never stopped running. My 1941 Buick would get a little stumbly after a long highway drive or a prolonged period of idling on a hot day and had to wait until fresh fuel got to the carburetor at driving speed in order to run properly again. Or I could just turn on the electric fuel pump when I'm on an off ramp in preparation for it to start cooking itself when I stop and the engine goes to idle. After shutting it down, restarting is easier once you fill the carb back up with fuel, regardless of temperature.

 

As I posted earlier, if anyone is going to have headaches from ethanol gas and sitting around, it's going to be me. Hundreds of cars sitting around for weeks or months, all different makes and models, all with different standards of maintenance and restoration, and I have yet to have a failure that I can trace to ethanol beyond the aforementioned gooey gas tank or a brittle fuel line. Solvable problems.

 

First, get rid of all the rubber in your fuel system. No rubber hoses. Voila, one major ethanol failure point eliminated. Rebuild your carburetor and fuel pump using modern kits, not NOS kits, that have modern ethanol-resistant materials (Jon's kits are superior). That's the second major failure point. And finally, install an electric fuel pump in the system somewhere, regulate it down to an acceptable level if you have to, but you need that cool, pressurized fuel when it gets hot. My '29 Cadillac has been running happily for a decade on a fuel pump regulated down to about 1 PSI. I'd love to convert it back to the vacuum tank, but the thing works so well that I'm loathe to change it and will keep the electric pump on a check valve as a back-up nonetheless. 

 

This really is a solvable problem. Ethanol isn't the end of the world. You're not a failure or a hack mechanic if you use an electric fuel pump. Ethanol isn't like pouring acid into your engine. You don't need to hunt down special gas to enjoy your old cars. You DO need to understand the problem better so you can adapt to the situation and tune your car to operate correctly under these circumstances. Ultimately, the key to solving vapor lock is to get fresh, cool, liquid fuel into the carburetor as quickly as possible and most cars are OK to go from there. Whether you do that with an electric pump, pouring gas into the carb throat to get it started, running it at a high idle after it fires, whatever. The secret is fresh, cool fuel moving through the carb. 

 

My numerous screw-ups are well-documented and I'm not a professional mechanic, but I get this part right on all my cars because I simply don't have the patience or willpower to be stranded by the side of the road. If that's what I have to do to keep the monster in his box, that's what I do and I do it well.

[SC38dls]

I used a grapefruit to insulate the fuel pump on a 39 Pontiac (May be off a year or so) of a friend when we were driving it back to Chicago from Nebraska. Every time we shut it off it would vapor lock. The only thing we could find was a grapefruit so we cut the top and forced it around the pump as best we could and it worked for the rest of the trip. The smell wasn’t too bad either. 
dave s 

[padgett]

Living in hot climates I've seen it all. As said the only reason for kerosene or diesel addition is to extend a limited gasoline supply.

Never had an issue once I started rerouting fuel lines away from manifolds or blocks. Have also added shields (Chevvy big block shield on a SBC starter) & used a thermal wrap on the headers before but then I am not a "stock is stock" person.

[Ben Bruce aka First Born]

Or, just do as I did.😁

 

  Ben

 

  

[PFitz]

33 minutes ago, padgett said:

Living in hot climates I've seen it all. As said the only reason for kerosene or diesel addition is to extend a limited gasoline supply.

Never had an issue once I started rerouting fuel lines away from manifolds or blocks. Have also added shields (Chevvy big block shield on a SBC starter) & used a thermal wrap on the headers before but then I am not a "stock is stock" person.

 Not to extend fuel. A fuel system engineer friend said adding Diesel was to lower the vapor pressure as it mixes with gasoline. This was not during the gas shortage years, but long after in the late 1980's when there was a couple of years of rampant vapor lock problems because the fuel companies let the Summer gasoline vapor pressure get too high, until the Feds cracked down on them. I only found out about that vapor pressure rise through a friend that is a member of SAE, because it never made the news reports. 

 

Paul

[Marty Roth]

45 minutes ago, PFitz said:

 Not to extend fuel. A fuel system engineer friend said adding Diesel was to lower the vapor pressure as it mixes with gasoline. This was not during the gas shortage years, but long after in the late 1980's when there was a couple of years of rampant vapor lock problems because the fuel companies let the Summer gasoline vapor pressure get too high, until the Feds cracked down on them. I only found out about that vapor pressure rise through a friend that is a member of SAE, because it never made the news reports. 

 

Paul

 

This confirms what I learned from a grizzled mechanic along the way from the Texas-New Mexico state line to Raton Pass, using my 1978 Suburban with the 454 ci big block to haul my enclosed vintage Tow-Eze trailer and tour car to the 1990 Colorado/Pikes Peak Glidden Tour. The big block Chevy had been dealing with vapor lock in the extreme 100 + degree heat and high altitude plus trailer hauling in the face of strong headwinds. When I stopped for gas at a very old station along the way, I asked for premium gas because of the vapor lock. The old-timer who ran the place suggested using at least 10% diesel and the lowest octane gas. At first I thought it didn't make sense, but he explained the reasoning in a somewhat non-technical manner. I followed his advice and soon noticed dramatic results in improved driving ability. I've followed that advice for the past thirty years and share with others - because it works. It worked in the 1978 Suburban back in 1990. It worked in the 1941 Cadillac at the Oklahoma City Glidden Tour, and it works today when facing the same type of issues. 

Edited July 19, 2020 by Marty Roth
typo (see edit history)