PatrickP

My '85 owner's manual indicates,when discussing oil, that "Porsche does not recommend" oil additives. I am wondering if perhaps in that last 15 years since an additive has been developed (i.e Slick 50, Tribotech, etc.) that Porsche would "approve" or regardless which would perhaps add to the life/performance of my 928. Interested as an oil change is in my near future. Thanks

Ed Ruiz

I find it is cheaper in the long run to use Mobil 1 and nothing else. In the Spring I put in 8 quarts of 15W50. In the Fall I put in 4 quarts of 5W30 and 4 quarts of 15W50 (which yields a blended 8 quarts of 10W40).

To the best of my understanding, all new Porsches come from the factory with Mobil 1 in them. I very seriously doubt Porsche AG would recommend any oil additive given that they are either being paid to use Mobil 1 or are getting it at a significant discount.

[ 07-06-2001: Message edited by: Ed Ruiz ]

PatrickP

Thanks Ed:

I had heard that there might be a problem with synthetics causing leaking. Legitimate concern?

Ed Ruiz

Back in the early Mobil 1 days, it was a very thin oil. Also, rope gaskets were more common than now. (I think Oldsmobile may still be using a rope gasket somewhere.) As a result, if the engine's seals or gaskets had little weaknesses, they would start to leak like a sieve after Mobil 1 was added.

Today, a properly maintained engine will not have any more leaks with Mobil 1 than with conventional oil. The leaks will be costlier, since we usually take more notice of a leak when the oil is $4 to $5 per quart than when the oil is about $1 to $2 per quart. YMMV.

PatrickP

Okay, I'll probably give the Mobile 1 a try. Just paranoid about putting anything in the engine that might cause an expensive problem later. No Slick 50, etc., then, right?

DoubleNutz

SLICK 50! Dude stay away from the additives in this engine. The Nikisil bores of the 928 are absolutly bullet proof, (until you start adding additives that may damage them) I currently use Mobil One in the same fashion as Ed Ruiz, however I have been considering going to Amsoil, and I have NO PROBLEMS.

No further science is required on this except STAY AWAY FROM THE ADDITIVES.

p@

SHRKBIT

Hi, Patrick.

When I switched my '87 S4 to Mobil 1 it started dribbling oil on the garage floor. It just pointed out work that needed to be done, and sooner. You want to tighten any loose fittings and replace any bad gaskets anyway, right?

Ed Ruiz

That last response points out an interesting characteristic about Mobil 1.

It has extremely good detergent properties. It will clean-out accumulated sludge in about one or two oil changes. That sludge may be acting as an additional seal around aging and leaking seals and gaskets. When they are cleaned out, those weakened seals and gaskets are likely to start leaking.

That's the down-side. The up-side is your engine is alot cleaner, and will likely run smoother and cooler. YMMV.

[ 08-06-2001: Message edited by: Ed Ruiz ]

PatrickP

I guess that's my worry. Would the synthetic REVEAL loose fittings/gaskets or, especially with the gaskets, EXACERBATE the problem? I don't want to do anything that would, for example, cause a major head gasket leak which would in turn cost big $$$$ to fix before I able ready to put out the money.

Tabor

The main thing about synthetic oils is that, if you have an oil leak, it will leak more with the synthetic than the conventional. I was told that the individual molecules of synthetic motor oil were smaller than conventional oil.

Ed Ruiz

You won't get a head gasket leak if it is properly torqued down. Oil seals and gaskets that are being helped by a coating of sludge will very likely start to leak once the sludge is cleaned away by Mobil 1.

For me, I don't like sludge in my engine. If it means I'll need to replace seals and gaskets sooner than later, so be it. YMMV.

~ Merry motoring ~

[ 08-06-2001: Message edited by: Ed Ruiz ]

Darren '85S

Stay away from the additives. Each oil company formulates their oil with their own unique additive package. If you add others to it, you can change the characteristics. Also of interest is you can mix oils (even synthetic and conventional), but they should have the same rating (SG). I'm not sure if blending different weights (lie 5w30 & 15w50) is necessary, since Mobil 1 15w50 pours at -55 and out performs most conventional 5w30 in cold weather. I have a good article on oil (but only in hard copy, I could probably scan it in). Also of note is that synthetic oil does not combust like conventional, so although they maybe thinner and more prone to leak, they don’t get used (consumed) as easily. This keeps the oil a lot cleaner and if you use your 928 on open roads, you can probably go longer between oil changes.

SHRKBIT

I think there's more to it than detergent properties. In the case of my S4, the enhanced leakage began pretty much overnight. As I recall some fitting needed to be tightened.

[ 08-06-2001: Message edited by: SHRKBIT ]

Darren '85S

These are great articles on oil. I can't believe I found them again (I printed this out from a news group 7-8 years ago).

Snake Oil! by Fred Rau
More Than You Ever Wanted to Know About Motor Oil by Ed Hackett
Lubricants Notes from Redline
AMSOIL Notes

[ 08-06-2001: Message edited by: Darren '85S ]

M@951

Mobil 1 rates poor on this comparison. What is the deal?

http://www.1st-in-synthetics.com/racing_oils.htm