Hello everyone, I have a question about synthetic oil. I have a 1991 Corvette Coupe and a 1981 Z28 that I have been considering switching to synthetic oil. However, I was told to not use synthetic oil in older vehicles such as these. I was told it causes older vehicles such as these to leak oil. Has anyone else heard this before? If this is the case, why does synthetic oil cause older vehicles to leak oil? Thanks

 

go try it... and let us know....

 

Go here. http://www.bobistheoilguy.com/forums/ubbthreads.php
If you have oil leaks now, you more than likely will see more.
On the other hand, synthetic is better for extreme conditions such as cold and hot running conditions. More benefits, higher cost, more controversy etc etc.
Seriously, go to that website, it is the oil website.

 

Why do you want synthetic oil? Do you race your cars? If not there is no advantage to synthetic oil, petroleum oil is pefectly good for your cars. I have over 600,000 miles on cars I have owned and driven everyday and each for more than 100k miles with petroleum oil and no engine problems. You don't need it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

The molecule of synthetic oil is smaller than that of conventional oil so it can leak from areas where no leak was noted during previous use of conventional oil. If you see a damp area now around any seals, valve cover, intake and pan gaskets it might turn into an actual leak with synthetic. If it leaks you can either fix the problem or switch back to conventional.

Your 1981 Z-28 originally required an oil with an API rating of "SF." Current oil is API rated "SM" which is low in phosphorus, sulfer and ZDDP extreme pressure additives for emissions. There has been a lot of discussion about using later "SM" rated oils in older cars with flat tappet (meaning non-roller) cams because of failing cam lobes and tappets. The API claims ratings are backward compatible to previous generation ratings and says SM rated oil is recommended where SL, SJ, SH, SG were originally required but this is not proving to be the case out in the real world.

If you are driving an older classic muscle car or hot rod that has an engine with a flat tappet camshaft, you should be aware of the fact that today's "SM" rated motor oils contain much lower levels of anti-scuff additive called "ZDDP" (Zinc Dialkyl Dithio Phosphate). The level of ZDDP in current motor oils has been reduced to no more than 0.08% phosphorus to extend the life of the catalytic converter. Phosphorus can contaminate the catalyst over time if the engine uses oil, causing an increase in tailpipe emissions.

The lower ZDDP content is not harmful to late model engines with roller lifters or followers because the loads are much lower on the camshaft lobes. But on pushrod engines with flat tappet cams, the level of ZDDP may be inadequate to prevent cam lobe and lifter wear. In some cases, cam failures have occurred in as little as a few thousand miles of driving! This is even more of a risk in engines if stiffer valve springs and/or higher lift rocker arms are used.

To avoid such problems, you should add a ZDDP additive to the crankcase, or use an oil that meets the previous "SL" service rating, or use diesel motor oil or racing oil that contains adequate levels of ZDDP to protect the camshaft and lifters.

If you are installing a new camshaft in the engine, be sure to use the cam manufacturers assembly lube and follow the recommended break-in procedure. But you will still need to add ZDDP to the crankcase or use an oil that contains adequate levels of ZDDP for continued protection.

More reading on the subject:

http://members.themotoroilevaluator....dex.php?id=155

 

I forgot to mention Comp Cams is now offering an oil for engines with flat tappet cams. Called "break-in" oil possibly to get around EPA regulations. Any oil called "racing oil" is also exempt from EPA regulations and has the various levels of active ingredients necessary to protect competition engines.

http://www.compperformancegroupstore...&Category_Code

 

I agree with what Greg said. You can get ZDDP additives anywhere now just about, even STP oil treatment has it. There is now more debate whether its really needed as much as once thought in later engines (80's 90's). Synthetic oil is superior, especially on start up and high demand, it CAN cause leaks in older cars but one oil change and you'll see if it does or not, but I would use a good synthetic blend in a higher mileage engine that has been run this long on conventional then switch after rebuild.

 

 

For the Z28, I recommend Shell Rotella. Higher ZDDP and is a very good oil and cheap at Wal Mart. Its oil analysis are always very good. Bobstheoilguy forum highly recommends it.
The oil debate is just that, a debate, not quite global warming, but close LOL.
Good Luck on your choice.

 

GEZZZZ, jfb. Way too many exclamation points. Seems you're much too emphatic in your position and are ignoring all the testing that shows synthetic oil having definite benefits over petroleum based oil.

I tried to, but I just couldn't resist. Yea, I know, now I'll live to regret it. LOL

Jake

West Point ROCKS! Nation's TOP COLLEGE per Forbes Magazine!! Graduaton Day Parade 20 May 2010!!!

 

 

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!
There, Jake now that I have your attention. The L98 was designed around dino oil as was about a kabillion other Chebby small blocks up to the LT1. What jfb is saying is if you do not need the advantages of synthetic oil why change? Said another way, is the added expense worth the undefined gains?

 

I likewise use Shell Rotella, based on a HotRod Magazine, analysis in my 86. Actually, you should be fine with any oil meeting the standards for diesel engines.

I also use it in our newer cars because it is a better lubricant and I do not trust my government on environmental issues. I am an analyst working for the public in higher education and know how seldom decisions are based on research and science and how often they are about politics and publicity.

 

I use it in all my cars, and I just don't have a problem. Prior to using synthetic, I have changed out rounded lobe cams.
Even after doing a proper startup/breakin procedure, I still ended up changing a couple of cams.
Not any more......
On the older cars (1957) I use a synthetic blend.......3 quarts of synthetic, and 2 quarts of dino oil. When I add, I add synthetic.

 

I live in Norhern IN. and like the benifits of cold weather flow in synthitics. It's not just for race motors. considering start-up is when alot of your engines wear occurs it only makes sense to get it flowing faster in sub-Zero temps.
For a good all around oil in older/high milage vehicles I use a semi senthetic with some type of seal conditioner in its properties, This way you get the best of both worlds and save a few pennies in the long run.
I have heard good things about the Shell Rotella as far as wear goes. I use to run high HP outboard motors (2-strokes) if you want to get into some serious oil debates go to one if these forums. A proffesional race motor builder for outboards knows there oils. The first thing they ask when they tear down a motor is what oil were you using and what ratiomixing at.


I forgot to mention Comp Cams is now offering an oil for engines with flat tappet cams. Called "break-in" oil possibly to get around EPA regulations. Any oil called "racing oil" is also exempt from EPA regulations and has the various levels of active ingredients necessary to protect competition engines.

http://www.compperformancegroupstore...&Category_Code

HOLLY CRAP! they are proud of this stuff $63 a quart??????????????????

 

[QUOTE=Greg Gore;1572414048]The molecule of synthetic oil is smaller than that of conventional oil so it can leak from areas where no leak was noted during previous use of conventional oil. If you see a damp area now around any seals, valve cover, intake and pan gaskets it might turn into an actual leak with synthetic. If it leaks you can either fix the problem or switch back to conventional............

Yes synthetic oil will leak through gaskets more so than conventional oil.If you drive your car slowly & like my grandma conventional oil will work just fine,just change it every 3 months or 3000miles(whatever comes first).But if you beat on your car like I douse sythethic oil for the added engine protection.Synthetic was a factory fill for lt-1 engines due to the fact synthetic oil protects at a higher temp. & that way GM did not have to equip the lt-1s with an oil cooler.You can go longer between oil changes with synthetic but I personally change mine every 3000-3500 miles.But the worst thing you can do is not change the oil often(every 3000 miles with conventional or every 5000-6000 miles with syntheic) as this will cause engine sludge-you seen the commericals & I've personally seen sludge build-up in engines & when I show the customers they become believers

 

STP is ZDDP pretty much. Specially Treated Petroleum. Add this to regular oil changes, or just buy Schell Rotella

 

Thanks everyone.

 

It doesn't now but engines built back in the middle ages before 1970 or so did not have seals that were compatible with synthetic oils. Problem solved a long time ago, but your 91 has roller lifters and can use the current SM conventional oil with no problem and a lot less cost. YRMV.

 

I bought a Comp Cams camshaft for my 83 Camaro. It's a flat tappet cam. There was a note attached to the cam that talked about oil requirements. This cam and all the other flat tappet cams need Zinc and mageniese (sp?) other wise the lobes will wear out too fast and void the warranty on the cam. They suggested Rotella T, and other oils with zinc and mag. Now Rotella T is reduced in these additives. I found that Lucas has an additive with zinc and mag. Also Joe Gibbs has an additive. Valvoline has a racing oil with zinc and is available in AutoZone and other auto parts stores.