Synthetic lubricants VS. Petroleum

[Bob Lanham]

I checked the archives on this, I know its been done before. It seems like most of the advice I have seen recommend using synthetic, but I saw one post from a purported salesman of automotive lubricants that they should not be used in pre-1982 cars because the seals would leak. I have a 69 427/390 that I was thinking of converting to synthetic due to lower temps. Will I have a problem with leaking? Which story is right? I really like the idea of lower engine tmeps.

All comments appreciated.

[Duke W.]

Re: Synthetic lubricants VS. Petroleum

I assume you are talking specifically about motor oil. Based on the research I've done, I don't think synthetic motor oil is justified on a cost basis, particularly on a car that has low annual mileage accumulation. The primary benefit of sythetics is greater resistance to oxidation. If I had to drive from California to New York and back and knew I would not have a chance to change the oil until I got back, I would use a synthetic. For a daily driver I change oil every 5000 miles, which means about three times a year. For my low annual mileage cars (1000-1500 per year) I change the oil once a year. Check out Pat Bedard's column in the November Car and Driver. A motor oil expert he interviewed recommended a heavy duty oil (API spec CF-4) designed for diesel engines. These are generally mineral oil based, but have a higher dose of critical detergent, dispersant, and anti-corrosion additives than conventional spark ignition engine oils (current API spec SH). The expert said that seldon driven cars, in the long run, may suffer more from corrosion damage than wear.

On the other hand, I'm a proponent of sythentics in the gearbox and diff. Changing the oils in these boxes is often overlooked, but a 30,000 to 60,000 mile interval is reasonable, and on a collector car this is a long time, so the cost is justified.

It's noteworthy that GM fills the C5 with sythetic at the factory, and recommends it for field oil changes, but they also elimiated the oil cooler that was equipped on some C4 configurations. During top speed testing the press reported oil temperatures of 300 degrees on the C5 which is way too high. The oil may resist oxidation at this temperature, but it will fry all the gaskets and seals just the same. My choice would be to install an oil cooler to maintain engine oil temperature in the 180 to 230 degree range, with a slow down limit of 250 to 260.

Apparently there is some chance of oil leakage with either a synthetic or the CF-4 mineral oils, and this is primarily a function of the additive package. If your engine has been rebuilt the seals and gaskets likely utilize more modern materials, which should decrease the chance of leakage, however, if it is an original factory built engine, the chance of developing a leak is likely higher.

The truth is that there is no "correct" answer to this question. It comes down to a somewhat subjective choice once you have determined all the "facts" involved, including the economics.

Duke

[Rob Brainard]

Re: Synthetic lubricants VS. Petroleum

Bob, There was a post awhile back from a fellow who was having problems with fouling sparkplugs. As it turned out, he was driving the car such short distances, it never warmed up enough. The same goes for engine oil in that if you don't drive your car far enough or long enough you will end up with condensation and fuel polluting your oil. While synthetic oil claims to have superior ability to suspend contaminates, who wants to have them floating around in your oil. So, it comes down to "How do you drive your car?" and you then can make your decision. I have one car with Mobil One in it and I don't know what I'm going to do this spring. My other two cars will definitely get the oil changed. For the person driving their car 1500 to 2500 miles a year, I don't think the cost of synthetic oil will reap any benefits. It is more important to heat your engine up completely and the condensation etc. will be allowed to form.

[Rob Brainard]

Re: Synthetic lubricants VS. Petroleum

Bob, Correction to my post. ---- Last sentence -- "Condensation will NOT be allowed to form".

[Doug Flaten]

Re: Synthetic lubricants VS. Petroleum

I started using Mobil 1 in my Panhead Harley last year and did not notice any increase in leakage. (I ain't gonna say that it don't leak.) I switched oils for the higher temperature stability and the fact that Panheads have poorly designed lubrication systems. Old Panheads run oil to the heads via a passage running the length of the cylinder. The oil is cooked by the time it reaches the head. Anyway, due to fuel contamination and condensation, I still change the oil at 3,000 mile intervals. At least I was doing that until an old lady pulled out in front of me and broke my pelvis in November. I believe that old carburetors and old cars tend to contaminate the oil and shorten the lubricant's life more than the actual heat and stress. They just get dirtier than today's engines and need more frequent changes. Because of this, I do not use synthetics in the car since contamination is of larger concern. I would not use them in the air cooled engines of my bike or lawnmower if I did not think heat was a larger concern.

[Duke W.]

Excellent point, Rob

This seems to be a general problem with collector car guys in general - they don't drive them enough. Or they start then and let them idle for 10 or 15 minutes to "warm them up and circulate the fluids". They'd be better off not starting them if they don't take them out for a drive. Most wear occurs during cold start and warm up, so if you're going to start it up, take it for a drive. Drive it for at least 30 minutes at operating temperature and have some fun. Corvettes should have their legs stretched once in a while, like a good race horse.

I do disagree with your comment that synthetics better suspend contaminants. If you are using API SH oil either synthetic of mineral oil base, your blend does not have as high a dose of dispersants as the API CF-4 oils. Dispersants, which are part of the additive package, are what hold contaminants in suspension, which are then flushed out when the oil is drained.

[Rob Brainard]

Thnax Duke, Re: But

Duke, I can't disagree with you with regard to suspension of contaminates [because I have no real knowledge], but let me throw this out. When Mobil One showed up on the scene they CLAIMED that you could change their oil at 25,000 miles. Regular changes [3000 miles] of the oil filter was all that was needed. At the time I owned a repair shop and was asked about this by my customers. I did some checking and found a fellow who was in the petroleum business and asked him about Mobil One. His reply was that the synthetics were able to have additional detergents that the petro based oils could not tolerate and that the function of the detergents was to suspend contaminates, therefore extending the interval between changes. What do ya think?

[Duke W.]

I'll give it a shot

I recall that Mobil 1 came out in the early seventies, and Mobil claimed a 25,000 mile change interval, but the OEMs were quick to respond that to maintain warranty coverage the oil had to be changed at their specified interval regardless of the type of oil. I think Mobil backed away from their 25,000 mile claim years ago.

In the years since, the API specs have changed several times. The problem in SI engines is the additive's combustion by-products are not freindly to catalysts so they have actually been REDUCED as we've gone from SE to SH. So the basic rule is that any of today's SH oils have less detergent, dispersent, anti wear, and anti-corrosion additives than the CF-4 oils regardless of the base stock. It's the additive package that's critical more than the base stock. A synthetic base stock is more resistant to oxidation, so it is generally more suitable to extended oil change intervals or high operating temperatures. By the same token I suppose it could be argued that if the oil doesn't oxidize, you don't need as much dispersent, but that brings us back to only having a benefit at higher mileage change intervals. You've got to get a hold of Bedard's column in the November C and D. As you might know, Bedard is a former Chrysler engineer, and the oil expert he interviewed really knew his stuff.

I don't know what the C5 recommended oil change is with the current Mobil 1 blend that is factory installed, but I suspect it is in line with most of today's recommendations which are 7500 miles or one year, whichever comes first.

Duke

[Duke W.]

P.S.

The title of Bedard's Car and Driver column, November 1999, page 23 is: Searching for the Right Oil for "Keeper Cars". He's specifically talking us, guys! I get the feeling that hardly anybody on the Board reads general interest car mags.

Duke

[George Daina]

The benefits of synthetic over fossil oil.....

is the ability of synthetic to "FLOW" at cold temperatures. This translates into increased bearing, piston, cam, etc. wear. The ability to lubricate at cold temperatures is also synthetic's achille's heel, as the oil will find any and all potential places to escape. A marginal seal will keep fossil oil in chech, not so with synthetic. Also, as mentioned before, synthetic will dissipate heat better than fossil.

When Mobil introduced Mobil 1, a techie came to one of our club meetings, movies and projector in hand, no VCR in those days, and showed us of two engines, one lubricated by fossil oil, the other by Mobil 1. They ran the cars 100K miles each, changed the fossil oil & filter every 5-6K miles, changed the Mobil 1 oil every 25K miles and the filter every 5-6K and topped of with new Mobil 1. After the 100K runs, the motors were pulled, and the fossil lubricated motor, you could see wear, cyl. walls scored, piston scored, cam * tappet wear. The Mobil 1 lubricated motor, nary a scratch, hardly any bearing wear, cross hatches in the cylinders, and not a mark on the piston skirts.

Quite impressive, been using synthetic from that day forward. Only recommendation I can give you, if the motor is in dire need of a rebuild, stay with fossil, else use synthetic, but if you find oil puddles, change back to fossil. The synthetic won't eat the gaskets, but will squeeze by them if they are marginal.

[Duke W.]

Re: The benefits of synthetic over fossil oil.....

Agree with the cold temperature flow. That's why synthetic multi-vis is typically rated at 15W-50. It has a better natural viscosity index. That's one reason why the Army uses synthetics in their vehicles. Regarding wear, comtemplate the following paragraph from Bedard's column:

He [the expert] mentions a brand of synthetic oil that debuted with miraculous demonstrations of its protection; while the engine was running, the oil was drained, and the engine kept humming past the end of the commercial. "Yeah, but in normal use, customers found premature engine wear" That's because the miracle molecule that allowed the engine to survive briefly with no oil had a long term disagreement with the zinc anti-wear additive.

Does anyone remember this commerical? I'd like to know the brand!

Duke

[Gary Schisler]

Re: Excellent point, Rob

Good point, gents, about getting the fluids warm by driving, not idling. So many folks think that this is idling is just as good as driving. As has been said here, driving the car a sufficient distance to insure that all is the fluids are at normal operating temperatures is far better.

The one area that I didn't see discussed here is the main "reason for living". Specifically, their ability to withstand shearing and burning at higher temperatures. Most synthetics are long string molecules that, by design or construction, withstand breaking down far better than petroleum based oils. I actually don't recall any literature or ads from any of the synthetic manufacturers that claim a better suspension of solids. The other thing they do better is, on start up, they tend to flow better, which is the number one culprit for engine wear. They also tend to have better resisitance to acid formation and suspension than petroleum based products. These last two reasons are the principal arguement for synthetics in today's higher revving engines, and hotter running, synthetics. They really don't offer significant advantages for classic cars. I will say that I use them in my 66 solely because the car gets its oil changed as soon as it comes out of storage (hopefully later this month). When I prepare it for storage in December, I change the oil to a petroleum based oil, drive it about 15-20 miles and then right into storage.

[Robert C.]

Re: The benefits of synthetic over fossil oil.....

Duke, I don't know the ad you're referring to, But we have this guy at all the local Dallas area swap meets with this engine running on a stand with no oil pan, valve covers, etc. I swear I've seen him at every swap meet for the last 5 years! This engine is still running! He sells some kind of super synthetic oil. I have also seen the Mobil 1 seminar, at two different club events. You WILL use Mobil 1 after you see their presentation. We should get these guys at an upcomming NCRS show. It is VERY interresting! Porshe also uses Mobil 1 in all its new cars and I think the new Jag also.

[George Daina]

Prolong or Prolog is the commercial......

Al Unser Sr. was seen pushing this garbage. Bad stuff, good lubricating qualities, but toxic on non lubricated engine components, like Alien's blood dissolving all metal it touches.

[Rob Brainard]

Re: Excellent point, Rob

Well Duke, I guess we got everyone's attention here!! All have supplied some excellent info. I think we can agree, that synthetic oils are good for their intended use and better in many instances. For our Vettes [those we drive 1500 t0 2500 miles per year] it probably doesn't matter what we use as long as we drive them far enough to thoroughly warm them up. Thanx everyone for your input.