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Legendary Member
17 April 2000
Northern VA
I know this is one of the most beat up questions but here I go. I searched thru the past topics and the FAQ, so hopefully I won't get shot down by the FAQ Nazi.

My '94 with 43k is in need of oil change. From it seems on the past posts, people seem to swear by Mobil 1 Synthetic. I'd like to drive my car semi-aggressive, meaning redlining everytime I drive, and several track/solo events per year. However, here's my dilemma. It seems from the service record that the previous owner only used regular oil when doing oil change at the dealer. I have heard plenty that switching from conventional oil to synthetic can result in oil leaks....this I need to avoid. Considering the age and mileage on my car, I"m not sure whether it's still safe to switch or just stay with regular oil? What doyall think?
I think that business about causing oil leaks either (a) is an old wives' tale, or (b) only applies to cars that have been so poorly maintained (never changing oil) that they built up sludge in the engine.

If it were my car, I'd change to synthetic and not give it a second thought.

Originally posted by nsxtasy:
I think that business about causing oil leaks either (a) is an old wives' tale, or

That is what I used to think as well. I dont know if it was a coincidence, but both cam plugs started to weep oil within 2 months of switching to a synthetic blend. It doesnt seem to leak much after I got it fixed.

Ive contemplated switching back to regular oil for the past year, but havent done much about it since there havent been any leaks in a while.
Switch. If your car leaks with the proper weight of either regular or synthetic oil, the oil is not the problem, it is the symptom.
I agree with Lud and would add that the only reason it may leak more is that the synthetics flow like a lower viscosity oil, which is part of the reason why they are better. Changing from regular to synthetic on an older car may "find" more leaks, but not cause them. I can't think of a single reason not to change. Synthetics are better, period.

[This message has been edited by sjs (edited 29 May 2001).]
It seems like it'll be a good idea to switch. The car's been maintained fairly well but not extremely well...meaning the oil change has been 3000 mile period and not 3month period but considering the guy never drove it in the cold or dusty condition, it shouldn't be too bad. Going Mobil 1!! I hope it's not much of a stab on my very thin wallet....hehe thanks for the words
There are two reasons the leak problem happens when switching. First, synthetics have significantly better detergent properties than most conventional oils. Second, the gasket material used in some older cars shrinks over time. So, switching to a synthetic on a very high milage older car results in the synthetic cleaning out all the gunk that built up around the old gaskets and you get oil seeping out.

If you get a leak with the synthetic, the oil is not the problem, it is just showing you a gasket that is not properly sealed.
Going Mobil 1!! I hope it's not much of a stab on my very thin wallet

It will help your wallet that the dealer near your house (top-notch service department, with the most NSX customers of any dealer of the nine in the Chicago area) doesn't stock synthetic 10W30, so you won't have to pay the dealer markup when you buy it at the store and bring it along.
I got this response from Mobil about Mobil 1 synthetic. Pretty much what you guys said, but I figured I'd post it.

Thank you for your inquiry.

Mobil 1 can be used in older vehicles with high mileage on them .
However, in older vehicles, if there is a problem with oil consumption
or leakage, it may not be economically wise to convert to Mobil 1 until
such mechanical problems have been corrected.

Mobil 1 is fully compatible with the elastometric materials from which
automotive seals and gaskets are made. In fact, Mobil 1 meets the
requirements of seal performance tests established by a number of
manufacturers. In vehicles which are in good condition, there should
be any problem with compatibility.
However, if the seals have hardened and have started to shrink, you may
notice some seepage.

my recomendation if you change to syntetic, witch I recomend, is to change the oil (to syntetic) and filter, run it for a few houres and then change the filter again and then top-off with oil. I've noticed that syntetic oil seems to "flush the inside of the engine clean" so the filter can get clogged. I have done this trick with a couple of turbo engines, and it worked OK. never had any problems with lekage. can be worth the few extra buck to sleep well at night.
FYI...I just had my clutch replaced by our Acura dealer and while they were at it I had them switch me to Mobil 1. My '91 has 94k miles on it and had no oil leaks before or since. Also the oil change just prior to this one I had the Bilstien Flush operation performed on my car to clear out any sludge build up. Don't know how well that actually worked but so far so good.