My recently aquired 1980 sat for four years prior to me getting her because of a fuel leak. I found and repaired the leak and drove it for about 500 miles at which point a got an oil change ( a few days ago). Prior to the oil change I noticed a few specs of oil on the garage floor now and again but now every time I look under her there is a few diffrent oil spots ranging from 3 inches to 5 inches in diameter under the oil pan and filter areas. They dont even look like new oil, it is dark like it has been in there forever, also when I check the dipstick the oil in the motor looks alot older than the few days its been in there. I know I need to change the valve cover gaskets and possible the head gaskets, could that be a cause to the problem and if so is it a tough job for a novice like myself to handle as I would like to start working on this car myself but have not had too much experience working on cars. whatcha guys think could be the issue. PS I also put a synthetic blend oil in her..... any help would be welcome...thanks..

Many areas to check. Rear main seal. Oil coming down the back of the block from leaky valve covers. Distributor shaft. Temperature sending unit leaking. Pan gasket. Oil filter on tight enough?
I am sure a mechanic can come up with a couple more.
Take it to a trustworthy shop for a look. They may charge you a few bucks to put it on a lift, but worth it to get your mind settled and a plan of action.

The most probably cause for the leaks is the use of the Synthetic motor oil. I know it sounds odd, but believe me, it causes them. Synthetics are GREAT for newer engines with good gaskets. However, if you go from conventional to synthetics in an older engine, one that already has a small leak especially, it will get worse. The smaller molecule size of the synthetic is why it happens, according to my reading anyway. My advice would be to go through with all new gaskets then use synthetic exclusively. If you have to pull the heads and all anyway might as well put a new pan gasket and rear main on there while you're at it and have all new seals. Good luck.

BINGO!!!!! My M-21 has never leaked as much as when I switch to RED-LINE NS gear oil. Nothing against the product, it's great, but every time I look underneath the car I see money on my garage floor (it's not cheap).


JR - Miramar, FL

Thanks for the replies... Can you guys think of any reason that the oil is so dark already with under a couple of hundred miles....

Once more. I am not an expert, but have to rely on what manufacturers say about their product, then make a decision. Valvoline makes an oil called Max Life, in all weights that is in a red container. It is made for older engines, and has different additives. I am in a hot climate, and am using it in my L82.
It is not going to help your leaks, but from reading how it is formulated, it cannot do any harm, and may be helping more then I know.
Check out their web site for more info.

Davii is on the money with what he said about using synthetics in an old engine that has not been overhauled or had gaskets, etc. replaced. That has been brought up several times about where to use synthetics.
Boatman

hey, its all worth looking at, thats why i needed some input from my fellow c3 owners.....thanks again

It's very dark due to its excellent cleaning and flow qualties. There has been sludge and dirt in the engine for years, even in small quanties. The new oil has loosened and disolved the crud, and suspended it in the oil. After sitting several years, this would happen with regular oil, much more so with synth. Put about 500 to 1000 miles on it, and change it again. This could go along with leak repair. Sounds weird but drive it enough so all of the leaks that are going to start do start, so you won't have to do them one at a time. 500 to 1000 miles.

Ken Styer

Thanks Ken.. Sounds logical to me....

Your leaks are most likely coming from a combination of a couple things. One they have strunk and gottne brittle, and secondly when the engine gets hot it expands and that makes the shruken gaskets seal even worse. This happens with all engines the older they get. The only remedy is to install new gaskets. Buy the best gaskets you can afford. Gasket technology has come a long way in the past 20 to 30 years.