: Different Oil for Leaky Seals?

04-06-04, 03:21 PM

Everyone here has been such a help to me in the past. Thanks.

My 97 Deville has an oil leak from the rear main seal that isn't too bad (about 1 quart every 1000 miles) but it leaks right onto the exhaust manifold causing bad smelling smoke to leak into the car when not moving. Sometimes the smoke is visible coming underneath and through the grille.

First, should I be worried about fire? One mechanic told me yes, but I read the the flash/combustion point of motor oils are generally 400+ degrees F. I am not sure what to do.

That brings me to my second question. Would it make good sense to use an oil that has a high flash point to reduce smoking? This website sells a smoke-free oil based on this principle:


Is this a scam?

Thanks very much,

04-06-04, 04:05 PM
Not to sure if that fire proof oil is a scam, but my wife used to own an 89 Bronco that had a serious oil leak, it would leak oil directly onto the exhaust manifild every time you went up a slight upgrade... It did this for about 1.4 years, never had a fire.. Not saying that it was perfectly safe, but I doubt that the exhaust manifold heat (though high) is enough to ignite oil..

One thing to think about, if your car every overheats, the exhaust manifild might get hot enough to light that oil (?) Anyone?

04-06-04, 04:20 PM
I would get it fixed..... I dont like petroleum products falling on hot objects, just my opinion.....

If anything would work you could try using a oil that is thicker and maybe one designed for higher mileage cars.....

If your running a thinner oil (like a 5w30 or 10w30), I might try a 10w40 or something along those lines... maybe valvoline max life, it says it swells seals, its at least worht a shot!!

04-06-04, 05:13 PM
Are you really sure it's coming from the rear main seal? If you have oil in the valley under the intake manifold it will run out a hole drilled in there and down the back of the block which would appear to be a rear main seal.

Just a thought. Lawrence can jump in on this one..

04-06-04, 05:36 PM
I agree..... i think it might be a valve cover, in my experience!

04-07-04, 12:29 PM
Thanks everyone. I'm not entirely sure whether it was the valve cover gasket or the rear main seal-I'll have to check with my mechanic. In either case, I spent $900 to have it repaired and it was great for about 50 miles. Then, the leak came back. Mechanic told me that some sort of internal vibration (not worth fixing) is the culprit. Without taking the engine apart, there is no way to know for sure, he said.

While he may be right or wrong, I don't want to spend any substantial amount more trying to figure it out, so I'm trying to get the thing to last as long as possible. I figure, the car is running well except for the bad smell and it's giving itself a natural oil change, soit may last me a while.

Do you if it's OK to use 10W-40 oil even though the oil cap & manual say only to use 10W-30? Also, is there a big difference in the thickness? Would it have a substantial effect on the leak?

Thanks so much for your help.

04-07-04, 12:35 PM
I think I would find another mechanic based on his reply. Get a 2nd opinion it can't hurt.

04-07-04, 03:48 PM
Your mechanic charged you $900.00 and didint fix the problem! What kind of excuse is "Its an internal vibration", he should of fixed that instead (whatever it may be) for $900.00.. I'd get my money back and go somewhere else.. Lucas Oil is extremly thick and supposed to clog up small oil leaks, its about $7.00 a quart and you shouldnt need more than 1 or 2.. Just an idea, but personally, I'd rather fix the problem directly..

04-07-04, 06:37 PM
Is it leaking the entire quart of oil per 1000 miles on the exhaust? If so, that's more than a minor leak and additives or special oils are usually a temporary fix, if at all. Also, leaks usually get worse with time. Don't add Lucas oil. It biases the balance of additives in your oil, making the oil overall less effective. I would stick with 10W-30, and a high milage type oil if the engine is older.

I too wonder if you got a raw deal from the guy who charged you $900. Maybe you could complain to the same mechanic/shop about the poor first round of service and use that as leverage for a discount in the second round of repairs to correctly resolve the problem.

04-07-04, 08:24 PM
Theres only a small diffference of 40 weight oils that 30s.. I like them because they will build more pressure during running temps, as the 30 weight might be a little on the thin side.....

Youll be perfectly fine, but swtich to a thinner oil for the winter time if you live where its cold!

04-08-04, 05:12 PM
I hear that 20W-50 is better than 10W-40 because it contains less additives. Has anyone tried 20W-50 or even 5W-50?

04-08-04, 06:57 PM
I wasnt aware they made 5w50.... there would have to be a lot of vicosity enhancers to qualify for a 5w50...

Id still go with the 10w40 at 90 day intervals... 3500 miles or so, if your running dino...

04-10-04, 12:19 AM
There is another recent thread that talks about using 10W-40 oil instead of the recommended 5W or 10W-30. My opinion is that unless you know that someone with a similiar situation (similiar engine and similiar problem, etc.) improved their situation by going to a 10W-40, for example, stick with what the mfr recommends. As for the very wide viscosity range oils, they are not recommended. There is a website, bobistheoilguy.com that beats the subject to death. Basically, a milti-viscosity oil starts with a lighter viscosity oil (typically 5 weight or 10 weight) and blends in molecules that polymerize (expand) when heated. This polymerization causes the oil to behave like a higher viscosity oil that thins less (not thickens) with temperature. Polymers, however, deteriorate for a variety of reasons. I am not up to speed with the chemistry but I can tell you that it is best to go with an oil with a narrow viscosity range since it has fewer of these molecules (and in some cases, such as Mobil 1, none). I live in Louisiana and I use a 10W-30 year round as it doesn't get too cold here. The "high milage" oils bias the additive package slightly in favor of things that tend to occur with older engines, especially valve stem seals and seals/oil leaks in general. They may help a little or they may not. Some additives are for people trying to harvest what's left of junk they drive, like those smoke-be-gone additives. It sounds like your vehicle is far from junk. If the vehicle looks and smells respectable, maybe you could just keep adding oil or get it fixed the other way ($). Delimma, yes. I know it hurts. Too bad viagra for cars does not exist.

04-10-04, 09:24 AM
You make good points, but the additives that they use will NOT deterioriate any appreciable difference after 90 days, and what you should be changing your oil at anyway!!!!

I dont really care about the oil life monitor, if you REALLY care about your car youll change the oil often... Its the best (and really cheap) way to keep your car running good and long!

04-10-04, 12:35 PM
I had a similar condition on my 93 STS. It was actually the oil pan bolts and oil manifold just above the oil pan that leaked.

As a short term solution I got a piece of sheet aluminum from the hardware store. I cut it into a rectangle shape about 6"x8", slightly rounded the corners and with a little trial and error slipped it up and over the exhaust cross under pipe to deflect the oil from the pipe. Basically creating as big an "umbrella" over the pipe as I could. The sheet aluminum is easily cut with heavy sissors and will not burn.
Another oil smell source is oil being blown back to hit the main exhaust pipe, right where it joins the catalytic converter. There is a large neoprene flap, that attaches to the frame, that is there to deflect oil from hitting the exhaust pipe; is it missing?


04-10-04, 01:44 PM
For what it is worth, on my 95 sls that I bought used, The wet pan and small leak that I noticed, is much less today than before. I run Valvoline Max life, 10/30 in cold temps and Vmax 20/50 in the hot months. Seepage is much less, but hasn't gone away. Doesn't bother me much anyway. Car runs fine. 141k miles anyway.

05-07-04, 05:24 PM
:coolgleam On an oil-nutball board I belong to, somebody claimed that Valvoline Max Life no longer has the extra esters in it to swell seals but the Pennzoil and Castrol high-mileage oils do. .02.