Can I use Synthetic Oil?

[Guest James Conkwright]

Hi, I just got my engine completely rebuilt in my '50 Special. I was wondering if I could use Synthetic oil?? Thanks

[Guest]

break it in with mineral based oil first, most people say to use synthetics

after 10,000 to 20,000 miles, I knew a guy that had rebuilt his vw type 1

engine and started it up with mobil 1, it sized up after a few miles.

[Jyrki]

Synthetic oil is too slippery for a break-in to occur, so use mineral oil for break-in, then switch to synthetic.

[Matt Harwood]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">break it in with mineral based oil first, most people say to use synthetics

after 10,000 to 20,000 miles, I knew a guy that had rebuilt his vw type 1

engine and started it up with mobil 1, it sized up after a few miles. </div></div>

Synthetic oils have to be the most misunderstood automotive substance this side of octane (which doesn't make more power or "clean out" the engine, by the way). Here's the straight dope:

They work better. They're slipperier, don't carbonize at as low a temperature, don't get as thick at cold temperatures and don't lose their lubrication properties as they age (not as quickly, anyway). They won't void warranties, won't eat seals and gaskets and don't cause engines to "seize" because they weren't broken in on conventional oils first.

I suspect what happened in the above situation is that there was some other defect in the engine that caused the problem. The issue with not using synthetics initially is to promote ring seal. On older cars where rings must "break in" over the first 2000-5000 miles, the synthetic actually works too well, limiting the friction between the rings and the cylinder walls, slowing this break in of the rings. Using a conventional oil will allow the rings to break in faster, then you can switch to synthetic. With modern engines, this is not much of an issue, since the rings don't need as much breaking in (Mobil 1 synthetic is factory fill on Corvettes, Porsches, Aston-Martin, etc.). <span style="font-style: italic"><span style="font-weight: bold">It will not cause your engine to seize if you use it after a rebuild! This is an old wives' tale that just won't die!</span></span>

As far as leakage and destroying seals, many people blame the synthetic for ruining their gaskets because they don't understand what is happening. Synthetic oils are "more slippery" than conventional oils, and can squeeze into much smaller spaces because of their molecular structure (straight chains of carbon rather than clusters). Therefore, when you switch to synthetic, the synthetic oils will find their way through holes that conventional oils cannot. This is what causes the leaks, not the oil itself. The gasket has not been damaged, but holes that already exist that are too small for conventional oil are large enough for the smaller synthetic molecule to fit through, and you have a leak. On a new or freshly rebuilt engine, this should not be an issue.

Synthetic oils have greater shear strength and a greater affinity for hot metal. This means that it "clings" to hot engine parts better than conventional oils and tends to stay on the parts when you shut off the engine rather than draining back into the pan.

Some manufacturers of synthetic oils claim extended oil change intervals, and while technically the oil itself doesn't wear out, it does get dirty, and the only way to get those contaminants out of your engine is to change the oil. Therefore, I don't go more than 3-4000 miles between changes on my cars, even though they all use Mobil 1. It's just peace of mind for me.

Also, I should point out that any oil changed regularly will make your engine last forever, especially these low-speed Buick engines. The synthetic is probably overkill. Like I said, I like the peace of mind they offer, so I use them in all my cars--including the Buick when it is done. I used to race my Mustang, so it was subject to high-RPM, high-temperature operation where the synthetic would make a difference. I use it in our two Mazdas because they are high-winding DOHC 4-cylinders. I put it in my mother's cars because she is somewhat "haphazard" with her maintenance, and the extended service interval will prevent her from doing any real damage to the motor. I also use it in the winter because it flows better at low temperatures and lubricates the engine faster, in addition to the aforementioned "clinging" to the motor parts. But if you're good with maintenance, it is more than you need. If you're like me, though, the added peace of mind it brings is worth the additional cost.

Hope this helps clear up any misconceptions you might have. E-mail me with questions.

[Guest]

matt, i like your thinking on this...

i would add, that it's a waste of money on an open ventilated engine. these old engines, like to breath oil out the vent pipe and oil cap. for $7 a quart, it's a little to pricey on a car with cork gaskets.

Since you car is only a weekender, are you really going to wear that oil out? not likely...

Plus, it's alwalys fun to change the oil in the spring!

matt, let's hear you high test 93... theory!

[Matt Harwood]

My theory on high octane? Easy: if your car doesn't knock on the cheap stuff, you don't need the expensive stuff.

The technical explanation is this: octane is a measurement of a fuel's <span style="font-style: italic">resistance</span> to being ignited. With gasoline, this may seem strange, but higher octane fuel needs more spark energy to ignite than regular fuel. That is all octane is--a measurement of the fuel's resistance to ignition. It isn't some special additive that makes horsepower (though it is an additive--one designed to resist ignition).

OK, with that in mind, here's what is happening in a car that needs high octane fuel. For one, it may have high compression (some cars built today are inching back up towards 11 or 12:1 compression!). More compression creates more heat and therefore more power. But the down side is that it creates "hot spots" inside the combustion chamber. These hot spots might be the edge of a valve, a piece of casting flash, an edge of the piston, whatever. In some cases, these hot spots are hot enough to ignite the fuel charge without the spark plug (this is how a diesel works, by the way, which is why this is sometimes called "dieseling"). When you hear a car laboring up a hill knocking away with the A/C on, that is what is happening inside the engine. Something is hot enough to ignite the fuel charge prematurely. Needless to say, this is very, very bad for the engine. High octane fuel can cure this because it will resist igniting from these hot spots, and will only ignite from the spark, which is far, far hotter. Supercharged engines, turbocharged engines and heavy towing can also create additional heat (obviously), which will increase the octane needs of an engine. There may be some situations where your engine needs more octane (towing) and when it doesn't (driving in the winter with no A/C and cold temperatures).

A second cause of knocking that high octane can cure is ignition timing. Too much advance and you get the same problems with hot spots. Modern cars have knock sensors that tell the engine computer to retard ignition even before the knock becomes audible. The computer will push ignition up as far as it can without inducing knock, so it is always on the edge. This is where it is most efficient and where it makes the most power. Using high octane allows the computer to dial in the maximum specified amount of timing advance, making the most power possible.

Now the important thing to realize here is that the octane only allows the engine to <span style="font-style: italic">make as much power as it is designed to make.</span> It doesn't magically make a hotter explosion and extract more power than the engine can generate. It just allows it to run at maximum. That means that your 200 horsepower 3800 engine might be making only 185 horsepower if you run crappy fuel in it. Putting high octane in it will allow it to make the full 200 horses, but no more. And if there is no knock on the low grade gas, you don't have a problem and you're getting all the power there is no matter what. If it ain't knockin', you don't need the expensive gas. Guys who claim they can feel the difference are only victims of wishful thinking--the placebo effect.

And although the gas companies will try to tell you otherwise, the high octane gas doesn't have any cleaner additives that the lower grades don't. It isn't inherently cleaner running, either. It's exactly the same except that it doesn't detonate early. <span style="font-weight: bold"><span style="font-style: italic">That's it. </span></span>

In some cases, higher octane can even hurt your engine's performance. While I don't exactly know why, I seem to get better fuel mileage out of my 5.0L Mustang when I use 89 octane instead of 92. I can't detect any difference in performance, but I get about 40 more miles per tankful, which is very noticable in a car that is lucky to get more than 200-250 out of a tank.

In summary, it is estimated that gas companies derive up to 40% of their profits from high octane gas. It doesn't cost much to make compared to regular, and there are a lot of fools out there who wrongly believe that they will have some more power or a cleaner engine in their Cavalier if they use the "good stuff." Untrue, but marketing and folklore have done their part to ingrain this into the collective conscious of the motoring public. People think that they're getting something they're not. If your car needs high octane, it will only let the engine run as well as it can. If you don't need it, you're only throwing your money away.

And as far as our old Buicks, with compression ratios under 7.5:1, they'll probably run just fine on a mixture of <span style="font-style: italic">Aqua-Velva</span> and some Jack Daniels (joking, but they don't need expensive gas). The old cars don't need the high octane, and with their weak ignition systems, may even misfire on high octane. The best gauge is your ear--if it knocks, try going up one step in octane ratings. See if it improves. If so, don't spend any more on the top grade. If not, try the top grade. If it still knocks, you've got a bigger problem and should probably be thinking about an engine rebuild.

Hope this helps.

Oh, yeah, one other thing: it doesn't effect emissions, either.

[Guest brh]

Matt thanks for all the info! My 300 runs on premium, its 11:1 and knocks like nobodys business on regular. I thought I was doing my daily driver a favor and putting in premium once in a while. The car developed a nasty hesitation during the winter, the first question the dealer asked was what grade of fuel am I burning, when I told em he said the car was not made for premium. I used nothing but regular and the hesitation went away. I tried synthetic oil on that car also, the gaskets leaked so bad it literaly ran down the sides of the engine. Had to have them replaced because even going back to mineral oil did not cure the leaking.

[Guest]

my daily rice-burner driver (nissan 300zx) has an octane sensor... so, i do burn high test in it once in a while for fun.

my '58 cadillac has 10:1 compression and ping like crazy without high test. i thought about retarting the timing, but that's the fun part of driving 300hp.

the other note i would make about high test, is that it's suppost to have cleaning solutions in it for the fuel injectors... not sure about the need if any.

if you every get a turn up, they run the special fuel enjector flush thru the car...

[Gene Brink]

Two good posts, Matt. Funny how these two items keep coming up over and over when both have been addressed multiple times, on this site alone, and should be throughly debunked by now... I guess it must be human nature to assume that if it cost more it must be better.

[Guest]

ok.... so why do people buy marvins mystery oil?

<img src="http://www.aaca.org/ubbthreads/images/graemlins/confused.gif" alt="" />

[NTX5467]

Some good replies, Matt.

As for oil leaking past gaskets, that can happen even with mineral oils of different brands. One friend complained that he didn't like Castrol GTX as it leaked, but he loved the Pennzoil back then as it didn't--in the same engine. My machine shop associate (and old drag racer who, like others of his age demographics and drag racers, gravitates toward Valvoline) concurred with the leakage issue as he'd experienced it himself on his Chevy pickup. Key thing is that if one brand leaks and the other one(of the same weight rating) doesn't, you know which one is most likely to get into all of the nooks and crannies of the engine to lubricate, cool, and keep it clean in there.

As for the cork gaskets, there are different qualities and cork particle sizes between some brands. Once a cork gasket starts wicking oil through it, you can't stop it so you'll need to replace it to stop the leak. One reason I coat the cork gaskets I use with silicone sealer is to prevent that wicking from starting in the first place (and easier clean up when it's time for replacement, should that be needed).

Synthetic lubes can eat, er "degrade", some seals. For ages, Chevrolet pickups with the 9.50" rear axle (usually 3/4 tons) used no rear cover gasket, with silicone being the sealer of choice (which was "fashionable" for when that axle probably saw its first uses). When GM made the move to synthetic rear axle lube in those vehicles a few years ago, low and behold, they came out with a new rear cover AND a gasket to go with it. The reason? The new synthetic rear axle lube would degrade the silicone sealer that had previously been used (by GM's own admission). Such action didn't take place overnight, though, from what I suspect, but over a period of time.

I know people that use Mobil 1 in everything they have. I'm fully aware that it's factory fill with many modern vehicles and has been since the old Shelby Dodge turbos of the '80s. I haven't looked to see if there's any difference in the rings and such in the current Corvettes and other LS1 style motors that don't come with it from the factory--or if the original run-in oil in those vehicles is mineral based and then changed after the 45 minutes or so of run time those new motors get at the engine plant.

The recommendation for mineral oil during break-in times dates back to when Amsoil was one of the few synthetic motor oils around.

In one respect, if the machining of a vintage engine is done correctly, that engine should last longer than it would have when new regardless of which modern oil is used. The other significant item would be if the seals and such are of more modern materials or are accurate to what the engine came with "back when", I suspect and that would be the ultimate determination of how synthetic oil (and certain brands thereof) would be tolerated in that operational environment.

The point of whether the crankcase ventilation system is open or closed can be a factor too. End result, it's your money to spend and your judgment call on the type of oil you use after the break-in period.

If I was going to venture off into synthetic oil in a '50s motor, I'd first do the break-in period with probably a 30W oil (due to its greater viscosity stability) and then switch to a 10W30 or so at the first oil change. It would probably work ok to use the multiweight from the start, but I might be a little old fashioned. After the second 4000 miles or so, then you'd have an idea of how the oil consumption was going and then make a determination of the projected costs to step up to a blended synthetic or a full synthetic. I don't see any reason why a blended synthetic would cause any problems with the seals and such--at least right now. At the least, the lessened amount of synthetic would probably extend the time it would take to degrade the seals--if it happens at all. The price difference between the mineral base oil and the blended synthetic is not nearly as large as it is from mineral base oil to full synthetic. For many, I suspect it could be the better value of the three, depending upon what useage the vehicle sees and such.

Just some additional thoughts . .

NTX5467

[Guest]

Once you have used synthetic oil do do have to continue using it? I was told that you cannot change back to regular oil or it would ruin the bearings. Larry

[NTX5467]

There should be no issue with changing from synthetic oil after using it for a while. The low friction and related anti-wear elements would be diluted as the residual synthetic oil is replaced with regular or blended synthetic oil that replaced the full synthetic oil that had been used.

What you might notice is that the engine might seem to run just a hair less silky or quietly, but not worse than if you'd been using mineral oil all along. Nothing worse than if you changed brands of synthetic oil or from one brand to another in the mineral based oil, I suspect.

I know there used to be horror stories of people changing the brand of oil in an engine and it cratering soon thereafter. Something about the gunk inside the engine reacting and clogging up the oil pump intake screen? When I've bought a used car, I devised a method to make sure it was clean inside.

I'd change the oil and then, when it was 1 qt down, I'd add a can of Stewart-Warner Alemite CD2 detergent additive to the oil. When it got 1 qt down again, I'd add another can. By that time, what I could see through the oil cap hole would be very clean of residual accumulations. Then, I'd change the oil to whatever I was going to use (usually Castrol GTX) and let it go from there. That way, whatever gunk that needed to be removed would be gradually liquified by the detergent additive and removed when I changed the oil. It also allowed a progressively higher dose of detergent after the first had started the cleaning process.

Another thing I started doing back then was, when the oil was on its last little bit of being drained out of the hot engine, to pour a quart of oil into the engine to kind of help flush out any residual oil that might be in a low spot in the pan. Sure, it basically wastes a quart of oil in the process, but it also makes sure that there's more clean oil in the engine after the change. To me, the extra cost and time is worth it--but I wasn't using the more expensive full synthetic oil either--and it was a 5 quart oil change too instead of a 6 or 7 (or greater) quart oil change.

Similarly, don't forget to fully or partially prefil the oil filter (if you can) or filter cannister with fresh oil prior to installation of the new oil filter. Helps get things moving a little sooner upon initial startup after the oil & filter change too.

Enjoy!

NTX5467

[TomE_1953]

I put in 0-30W Amsoil in my 1953 Roadmaster before the trip to Flint and it ran cooler and smoother than with conventional oil. I did use 1 qt. on the 1,600 mile trip but that is normal for her. I also used Amsoil 90 wt. for the rear-end. The Amsoil rep. gave me a can of their penetrating spray and I used it on my rear window vents (they were very hard to open and were binding up). I sprayed into the rubber seal around each window and now they move freely.

I didn't see any oil leakage on or around the engine compartment as some people warned me before the long trip. I'm very pleased with Amsoil products and glad I switched over before Flint. Yes, it's expensive but worth it on a 50 year old engine (62K). <img src="http://www.aaca.org/ubbthreads/images/graemlins/shocked.gif" alt="" />

[Jyrki]

It should be noted that Amsoil, Red Line Oil and some other ESTER-based oils tend to swell the seals rather than shrink them like the most common synthetic, polyalphaolefin (PAO). While these ester-based oils are expensive, they outperform all other oils in every aspect.

[NTX5467]

The Amsoil version (similar in action and orientation to WD-40, but synthetic) penetrating spray lube has the added bonus of not attracting dust, making it ideal in dusty climates for lubricating anything that will be exposed (i.e., lock cylinders, hinges, etc.). When I had a good source on it, I used it and it kind of smelled like eau de bug spray, but worked well.

Glad it worked for you!

Enjoy!

NTX5467

[Gene Brink]

Been very busy at work and am just catching up on my important reading. It's a mystery to me why anyone buys Marvel Mystery Oil, Tommy.