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Gasoline questions/debate


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3 hours ago, W_Higgins said:

 

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

 

 

 

I have no first hand experience, other than personally never needing to do so, thus - no comment.

 

Jon

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Gasoline needs to have an octane rating of 87-91 to fit today’s car engines. Diesel fuel has an octane rating of 25-40.  Mixing 2% diesel fuel into gasoline will lower the overall octane rating by 1 point. Getting 10% diesel contamination  lowers octane by 5 points, which is enough to create problems in most engines. The octane depression rises linearly with increasing percentages of diesel fuel in the gasoline.

And that's just the first potential problem.

 

  • {Because diesel fuel is heavier than gasoline, it can sink to the bottom of your gas tank, resulting in the injection of both gas and diesel into the intake manifold or the cylinder. Depending on the mix, you can get partially-burned diesel fuel which leaves bigtime deposits on pistons, valves and spark plugs. You get a car or truck that runs terrible, and if you keep driving it, you can cause serious damage}
  •  
  • If enough diesel fuel gets in the cylinder, you can hydro-lock the cylinders, resulting in a blown head gasket, cracked cylinder head or other serious problems that can lead your vehicle down the road to a quick and final death.  This diesel fuel in the cylinder can also seep past the piston rings into the oil crankcase, diluting the lubricating oil. This can damage all internal engine lubricated parts resulting in major engine failure from rapid wear.
  •  
  • If unburned diesel fuel makes its way into the exhaust system, it will ignite in the catalytic convertor. The fire will plug the holes in the catalyst, destroying it and leaving you with a repair job well into the four-figures.
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This is starting to make sense to me, lowering the octane  with a hot engine and emissions (retarded) timing could reduce the vapor lock tendancy while the hot engine will burn the low octane gas quicker and more completely than when cool.

 

Had trouble understanding because I've always taken the opposite approach: keep the engine and fuel lines cooler and do not have an issue. Can see a strangled 454 pulling a heavy trailer would be worst case. OTOH I've pulled a tandem trailer over the Monteagle pass on a hot midday in July and never broke 200F. Just two different ways of dealing with the same problem.

 

rig3.jpg

 

 

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1 minute ago, Pfeil said:

Gasoline needs to have an octane rating of 87-91 to fit today’s car engines. Diesel fuel has an octane rating of 25-40.  Mixing 2% diesel fuel into gasoline will lower the overall octane rating by 1 point. Getting 10% diesel contamination  lowers octane by 5 points, which is enough to create problems in most engines. The octane depression rises linearly with increasing percentages of diesel fuel in the gasoline.

 

 

I was reading this earlier.  It's best to provide a source:

 

https://www.bellperformance.com/blog/accidentally-mixing-gasoline-and-diesel-fuel#:~:text=Diesel fuel has an octane,create problems in most engines.

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One other consideration with Ethanol fuels is the Ethanol is water soluble and ABSORBS water, if not isolated from the surrounding air absorbs a lot of water.  In a modern car the fuel system is sealed, has a sealed fuel cap and is isolated from ambient air.  My 31 Buick is wide open to ambient air and since I insisted on actually running a fully functional heat riser system I got a little object lesson on why I can't run ethanol fuel. 

 

The heat riser system on these cars is a plumber's worst nightmare, it uses 2 butterfly valves in 2 iron castings separated by a small inner exhaust pipe to carry exhaust gas back from the exhaust manifold damper housing to the heat riser casting between the carburetor and intake manifold, then an outer larger exhaust pipe that returns the exhaust from the heat riser back to the exhaust damper housing where it exits to the muffler, a boatload of linkage and a lever on the dash to control exhaust flow thru the  heat riser.  The outer exhaust damper to heat riser pipe is supposed to be sealed to the iron castings, probably originally with asbestos cord and on my car with a high tech refractory cement.   Before I switched to ethanol free fuel the exhaust had huge amounts of water vapor in it which sprayed out of every pinhole leak in the joints between the exhaust pipe and the manifold damper and heat riser castings.  It left white splatter all over the left side of the engine compartment.   As a bonus, one run on the ethanol fuel with the heat control lever in the Heat Off setting caused the butterfly in the riser casting to stick shut hard enough to buckle the rod that operated it from the dash control.  Can you say UPSET?  Wife said I said a few other things that I wouldn't put in a post on a public forum. 

 

So I decided to try the ethanol free route.  I had cleaned up the mess from the ethanol fuel run and the car sat long enough to evaporate the fuel out of the carburetor and I dumped the rest of it out of the fuel pump sediment bowl.  I started the car and to my happy surprise not one drop of water came from the riser system.  And- the butterfly in the heat riser hasn't stuck once since.  The water the ethanol fuel absorbs rusts internal steel parts and leave a white corrosion on other metals.  As others have noted it's not kind to rubber based soft seals or lines. 

 

My one complaint with the ethanol free fuel I found first at the local Shell station is that it was only available in premium 94 octane.  That's another problem for the elderly Buick engine which has a "High Compression" ratio (you've all seen one of these early Buick 8's with the red HC sticker on the valve cover haven't you?) of about 4.5-1.  A lawnmower engine has higher compression than that.  Then the problem becomes having the combustion cycle complete before the exhaust valve opens because the flame propagation rate of the 94 octane fuel requires more time to finish burning than is available from being touched off by the spark plug until the exhaust valve opens.  The higher the octane the higher the flash point and the slower the flame propagation.  That's not good for exhaust valves, as soon as they leave the seat in the head they lose their ability to transfer heat to the head and ultimately the cooling system- they get excessively hot.  I know the combustion cycle is not completing fast enough because i can hear rumbling out the exhaust pipe  I'm hoping to attack that problem on 2 fronts.  First- I now have a source of ethanol free (Marathon) fuel in 89 octane which should have a faster burn rate.  There won't be a problem with preignition with a 4.5-1 compression ratio.  The second approach I am carefully investigating is adding some ignition timing advance.  Buick suggests the total advance, initial advance of 11 degrees before top dead center plus the centrifugal advance not exceed 34 degrees.  That means if the centrifugal advance built into the distributor's mechanical advance is less than 23 degrees there is room to add some initial advance.  I'd actually be ok with a little more than 34 degrees total but not much more.  I'm out in the garage today determining what I have to work with.

 

Dave

 

My heat riser is sitting upside down on the bench but the heat control butterfly is clearly visible here shown in the OFF position.

Condensate from 10% ethanol regular fuel caused this butterfly to seize closed after on run.

HR 031.JPG

 

You can see the articulated linkage that coordinates the exhaust diverter valve with the heat riser valve.  The throttle cam arrangement

has no effect on the butterflies in the heat off position but in medium heat or heat on positions as the throttle is opened the butterflies

in the diverter and the heat riser move toward heat off position allowing maximum exhaust flow.  The diverter valve in this picture is

int he wide open or off position posing little restriction to exhaust flow.

HR 044.JPG

 

In this picture the exhaust diverter and heat riser are in the heat on position and the throttle is closed making for maximum heating.

HR 045.JPG

 

Here the heat control system is installed in the car.  Condensate sprayed out of the joints between pipe connecting the diverter valve

to the heat riser and made a royal mess of the air cleaner, engine paint and everything else in the area.  After I switched to ethanol free

fuel that never happened again.

HR 078.JPG

 

That's the instrument panel mounted heat control lever on the left side of the instrument cluster I restored.

IP 0042.JPG

Edited by Str8-8-Dave (see edit history)
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3 minutes ago, Pfeil said:

Gasoline needs to have an octane rating of 87-91 to fit today’s car engines. Diesel fuel has an octane rating of 25-40.  Mixing 2% diesel fuel into gasoline will lower the overall octane rating by 1 point. Getting 10% diesel contamination  lowers octane by 5 points, which is enough to create problems in most engines. The octane depression rises linearly with increasing percentages of diesel fuel in the gasoline.

And that's just the first potential problem.

 

  • {Because diesel fuel is heavier than gasoline, it can sink to the bottom of your gas tank, resulting in the injection of both gas and diesel into the intake manifold or the cylinder. Depending on the mix, you can get partially-burned diesel fuel which leaves bigtime deposits on pistons, valves and spark plugs. You get a car or truck that runs terrible, and if you keep driving it, you can cause serious damage}
  •  
  • If enough diesel fuel gets in the cylinder, you can hydro-lock the cylinders, resulting in a blown head gasket, cracked cylinder head or other serious problems that can lead your vehicle down the road to a quick and final death.  This diesel fuel in the cylinder can also seep past the piston rings into the oil crankcase, diluting the lubricating oil. This can damage all internal engine lubricated parts resulting in major engine failure from rapid wear.
  •  
  • If unburned diesel fuel makes its way into the exhaust system, it will ignite in the catalytic convertor. The fire will plug the holes in the catalyst, destroying it and leaving you with a repair job well into the four-figures.

 

2 minutes ago, W_Higgins said:

 

Gasoline needs to have an octane rating of 87-91 to fit today’s car engines. Diesel fuel has an octane rating of 25-40.  Mixing 2% diesel fuel into gasoline will lower the overall octane rating by 1 point. Getting 10% diesel contamination  lowers octane by 5 points, which is enough to create problems in most engines. The octane depression rises linearly with increasing percentages of diesel fuel in the gasoline.

 

I was reading this earlier.  It's best to provide a source:

 

https://www.bellperformance.com/blog/accidentally-mixing-gasoline-and-diesel-fuel#:~:text=Diesel fuel has an octane,create problems in most engines.

 

All good points,

but I'm talking about a carbureted 1978 Suburban back in 1990, and 80+ year old vintage cars today, as well as our former 1986 carbureted 454 ci Suburban - not today's cars and fuel injectedengines

I likely have well in excess of 50,xxx miles between both examples.

The mixture of diesel into the gas has yet to show any negative effects on any of the vehicles, and despite having added electric supplemental fuel pumps to just about all of our vintage rides, they are rarely needed if facing extreme conditions with the "magic" mix. Nothing is perfect, but it works for me.

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Like I said - two different approaches that both work. "One other consideration with Ethanol fuels is the Ethanol is water soluble and ABSORB water," Why various 'ol"s used to be sold as "Gas Line Antifreeze". Sometimes a good thing.

 

ps back in the day when a clutched fan (used with AC by GM) wore out, temps particularly at low speed, would rise. Because I can, my 80s cars with electric fans are reprogrammed to come in earlier: 185F LO instead of 215F with AC off and match to a 180F thermostat (computer cars are "all in" by then). I find that running my cars about 20F under stock makes everything under the hood last longer. 180F is also high enough for a single wire O2 sensor and cats to light off just as fast. Three wire are even easier.

I never remove a modern tubular cat, makes a good muffler and may not need anything else. Early flat cats were pretty restrictive (but had a drain plug).

 

Cars from this century are much better, '12 Jeep is the best tow car I've ever had. Will be AACA eligible some day, Chrysler warranty lasts until 2099.

 

& if have a need for speed, there's the Judge.

 

 

 

 

Edited by padgett (see edit history)
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1 minute ago, Marty Roth said:

 

 

All good points,

but I'm talking about a carbureted 1978 Suburban back in 1990, and 80+ year old vintage cars today, as well as our former 1986 carbureted 454 ci Suburban - not today's cars and fuel injectedengines

I likely have well in excess of 50,xxx miles between both examples.

The mixture of diesel into the gas has yet to show any negative effects on any of the vehicles, and despite having added electric supplemental fuel pumps to just about all of our vintage rides, they are rarely needed if facing extreme conditions with the "magic" mix. Nothing is perfect, but it works for me.

 The problem is the separation of the two fuels and a accumulation of diesel in the bottom of the tank, also if some of this unburned diesel finally  gets into your intake system and is unburned the catalyst you  have can make a real fire bottle going on, and  your 1978 Suburban has a catalytic converter. That is unless you removed it, which is illegal. 

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What is also being missed in this discussion of gas and vapor lock is a major part of the equation - that what goes into making gasoline is not the same throughout the Country. Gasoline is a blend of many chemicals that varies by state and company.

 

Back when as the follow along break-down vehicle for a national car club, I  was dealing with 12 cars with vapor lock problems during a week of  that car club's tours through central NYS. Some of the exact same year and model cars from out of state were doing fine,..... until they used up the gas in the tank from their home state and filled up on our NYS gasoline. Then their "I don't know what your problem is" expressions quickly changed to, "What just happened to my engine" ? 

 

Paul

Edited by PFitz (see edit history)
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That's the biggest issue I see with this rotgut that passes for modern gasoline- too many blends, even within states, to satisfy EPA and local ARB requirements. As an example, our gasoline here in Southern Virginia is sourced from a tank farm in Greensboro NC. Whatever they have to use, we get by default and Piedmont Triad area of NC has some pretty stringent requirements.

 

I can buy fuel sourced from Kenly NC tank farm and notice an immediate difference in drivability and fuel mileage.

 

2016 must have been another year the RVP was tweaked high. The fuel injected vehicles muddled thru but the carbureted 78 Olds wagon wasn't having it. Nearly impossible to start cold and vapor-locked more times than I care to remember that summer, until I started feeding it non-ethanol. At that point it ran as it always had.

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7 hours ago, PFitz said:

Gasoline is a blend of many chemicals that varies by state and company.

 

Also varies by season. The only part that varies between companies is the small additive package added into the tanker truck at the terminal. All brands get the same formula out of the pipeline at any regional location. Gasoline formulas are controlled by some govenrment agency. Like "Techron" Additive that other brands do not have rights to use. So a Shell delvery truck can fill up at an Exxon terminal as long as the driver has the Shell additive package to add to the tanker. 😉

 

8 hours ago, Pfeil said:

Gasoline needs to have an octane rating of 87-91 to fit today’s car engines.

 

Well, that depends....First on altitude! Denver area has 85 octane pump gas as the "regular". 87 is mid grade. 

 

Second, we are not discussing "today's car engines". Heck most made since 2012 can run 85% ethaanol! Sensors determine ethanol mix in the tank and run algorithms to fire the fuel injectors, timing, etc.👍 That's now 8 years ago....  In the 60s those would be valueless used cars.😁

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Many if not most updraft carburetor-equipped cars, including my 1922 Paige (6 cyl) and 1925 (6 cyl) and 1930 (8 cyl) Pierces have their exhaust downpipes at the FRONT of the engine.  Hot-day ambient air is pushed by the fan over the hot downpipe directly towards the carburetor bowl.  The fuel problem when these cars were built is exactly the opposite of our problem today:  then they needed to atomize fuel better by increasing the temperature of the fuel in the carburetor.  Accordingly, some wrap on front-mounted downpipes helps me a lot to solve today's problem--which is not vapor lock (a suction side problem) but percolation in the carburetor.

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Does anyone else find it amazing that cars made 100 years ago (when 32, 50, and 100vdc were common home powers. Remember AC-DC radios ?) can still run on today's gasolines ?

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Yet another thread about ethanol blend gasoline. Living in the DFW area we have had E10 forever and there are no sources of ethanol free gas reasonably close. In the last 15 years I have run every hobby car I owned on E10 without ANY issues except once - my 32 Cadillac V-12 was out of service for a long time, about 6 to 8 months. It had about 10 gallons of E10 in the tank and it separated so I had to drain and dispose of it. Every other car, which included 4 prewar and 5 50s / 60s cars, ran fine and were dependable using 87 or 93 octane E10. Yes, there was some tuning involved but nothing that dramatically affected the use of the car. The secret for me is keeping the tank at about 1/2 to 3/4 full and driving the cars on a regular basis so that fresh gas is introduced fairly often. Sure, I remember the smell of leaded Sunoco 260 going in and coming out of a high compression musclecar but we are not going back there no matter how much we complain about it.

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2 hours ago, padgett said:

Does anyone else find it amazing that cars made 100 years ago (when 32, 50, and 100vdc were common home powers. Remember AC-DC radios ?) can still run on today's gasolines ?

 

 The engines do not care. Only the carburetors do. 

 

  Ben

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12 hours ago, Frank DuVal said:

 

Also varies by season. The only part that varies between companies is the small additive package added into the tanker truck at the terminal. All brands get the same formula out of the pipeline at any regional location. Gasoline formulas are controlled by some govenrment agency. Like "Techron" Additive that other brands do not have rights to use. So a Shell delvery truck can fill up at an Exxon terminal as long as the driver has the Shell additive package to add to the tanker. 😉

 

 

Well, that depends....First on altitude! Denver area has 85 octane pump gas as the "regular". 87 is mid grade. 

 

Second, we are not discussing "today's car engines". Heck most made since 2012 can run 85% ethaanol! Sensors determine ethanol mix in the tank and run algorithms to fire the fuel injectors, timing, etc.👍 That's now 8 years ago....  In the 60s those would be valueless used cars.😁

 Whatever they did to the gasoline, it was enough change that when those out of State cars started filling up here at CNY gas stations, they had problems, too. 

 

After about two years the incidence of vapor lock was pretty well gone.  By 2002 we had over 100 cars touring, same area and even hotter weather that week. Record 102F in Syracuse the day we toured there. Only one car got stuck  due to vapor lock when we reached stop and go traffic in the city. A V12 with the fuel pump right next to exhaust pipe. A few minutes of my wrapping wet paper towels around the pump and we got it started again.   

 

Many I know have switched to e-free gasoline whenever they can get it. Just about every station here in CNY carries e-free 91 octane now, and it does make a noticeable difference,... even in how the engines perform when it's not hot weather. 

 

Paul

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27 minutes ago, Ben Bruce aka First Born said:

 

 The engines do not care. Only the carburetors do. 

 

  Ben

Is that why automotive engineers lowered compression ratio's and started using hardened valve seats in the early 70's when they knew leaded fuel was on it's way out??

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That was for emissions (Fed) requirements in the early daze. High compression led high temps which led to High NOx. Taking the lead out for the coming catalytic converters reduced valve lubrication and needed hardened exhaust (hottest) valve seats.  I could buy leaded regular at many stations into the mid-80s. Meanwhile Amoco Unleaded (in all grades) was a niche product and recommended a leaded tankful every fifth (from memory) tank.

 

Did a lot of studying while at GMI in early 70s & is when I started running cars about 10% cooler than stock. Everything under the hood lasts longer.

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I guess this has become academic (at least for me). The two gas stations that it makes sense to drive to have stopped carrying E0 gas. The chain's media person said they were having a hard time getting it due to the Covid and low oil prices so they just discontinued it.   The only place left to try is the airport, and I don't relish the thought of that.

 

Car is running fine on 91 - 93 octane E10 so I guess that's the way I'm going for the time being.

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"Car is running fine on 91 - 93 octane E10". I run 87 in cars designed for it, 93+Stabil+CD-2 in the Judge (12 heads are 10.25 & not hardened. If give trouble I have a set of 6Xs), and alternate 1/2 tanks of 89 and 93 for those needing 91. See no difference. Seem happy.

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