ODSharkBytes

Synthetic oil is just hydrocarbon molecules that are uniform and straight-chain. These are manufactured by assembling smaller straight-chain molecules into longer straight-chain molecules, similar to how polyethylene or polypropylene is created, except that the molecular weights are not very large. Petroleum-based lubricants will have these same molecules but also some branched-chain molecules and unhydrogenated molecules, which makes the petroleum-based oils a bit more susceptible to breakdown from engine heat and pressure. The breakdown products created are typically acid or base in nature, and besides losing lubricity, will promote corrosion. Mixing will not compromise either oil, and the additives are typically similar and provide properties such as metal corrosion inhibition, buffering of acidic or basic by-products, de-foaming, etc. No harm done IMO.

Andre Hedrick

I use 7 quarts of 20-50 and 2 quarts of Lucas !!!

jon928se

Mixing oils not a likely problem in the short term long term would depend on the mix .

10W30 is just too thin at high temps - I would say drive hard up a hill then look at the hot idle oil pressure, but I wouldn't recommend it.

IF you don't know the recent oil change history change chnage the oil and filter, aka treat it as an engione flush.

If the recent history is good and within the specified intervals just change the oil, and dump the old oil out of the flter then refit it.

FWIW my 88SE is running 10W70 Penrite, here in Sydney OZ which should be generally as hot or hotter than CA but is damn cold and wet at the moment. Hot idle OP is a tad under 3 Bar.

UKKid35

The Penrite site is very readable and explains the Zinc or ZDTP issue clear enough even for me to understand

Penrite on Zinc

hacker-pschorr

I run straight castor oil - does wonders for the exhaust ports.

Jim bailey - 928 International

Lifted from another forum....but a good read.."Since a 1997 court case brought on by Mobil against Castrol (in the US), and subsequently won by Castrol granted anyone to produce their non-PAO Group III base oil and sell it as a full synthetic, again, ONLY in the United States because anything can be bought or decided by the wrong people (courts, not scientists) in the US. So, since 1997 there has really only been one true synthetic oil available for sale in the United States, Mobil 1.


Well, I'm letting everyone in on a little secret. Castrol DOES sell a true synthetic in the US, it just doesn't make it here (which is fine by me). Autozone sells Castrol 0w30 "European Formula" Syntec. Look for the "Made in Germany" on the back of the bottle. See, in Europe the BS that is allowed to fly in the US isn't worth squat before a real set of government standards groups as in Europe. This is one of those few. Castrol SLX (now Castrol Edge). Note again, there are no other versions of Castrol or any other brand you can buy in a store on any given day other than Mobil 1 which are true synthetics.


There are racing specialties and what not, and "Amsoil" which while a true synthetic has some of the sleaziest marketing people in the world. Contrary to what they'd have you believe, Amsoil isn't the secret oil that most race teams use. In my 10 years of Rallying, Hillclimb and Time Trials I believe I've seen Amsoil once. Most people either use a high end conventional from Castrol or Valvoline, or Mobil 1 Synthetic.


Either way, if you DO look at the various tests online, you'll find that Castrol actually does indeed beat Mobil 1 on many levels (though not all), so either really will do well for your synthetic needs. Mobil 1 is generally a little on the thinner side of its viscosity rating (high number), whereas German Castrol (as it is referenced (or simply GC)) is a little on the thick for its equivalent viscosity rating.


If you are running a high performance engine, a turbo engine, a supercharged engine and/or care simply about providing your engine the best care you can in terms of motor oil, you've got those choices for synthetics and nothing else. Caveat emptor.


And if anyone is wondering, the reason why I specifically went for German Castrol is because it has been pretty much designed for the German motor manufacturers. It is the only oil in the United States (synthetic) that passes the stricter of VW, Audi, Mercedes, Opel, BMW and Porsches requirements for engine oil. ....." Much of what is sold as "synthetic" really is NOT but is simply ultra refined regular old Dino Juice think about that for a while .

morganabowen

Since we are on the topic of motor oil, I picked up a case of Torco Synthetic Motor Oil in a drawing at a car show. Is anyone familiar with this oil?? Can you use it in my 928??? Just curious. I just put it on e-bay the other day.

Bill Ball

That does look pretty good. One key point is the discussion of oils rated GF-4 - these are called "energy conserving" oils, and are a subset of the SM rated oils.
Doug has pointed out that GF-4 oils do not meet requirements for our motors as the HTHS is too low. This has casued a lot of confusion about SM rated oils. If the API "dounut" rating seal has GF-4 in the lower portion, avoid it. Otherwise, SM grades of 0W40 and 15W50, such as M1, are fine.

Here is a recent post on the 993 forum where Doug comments...
https://rennlist.com/forums/showthre...25#post5116525

So, the 10W30 synthetic used in this case should be examined closely. It may be GF-4. Even if not, it is likely it has too low of an HTHS.

FlyingDog

I have read good reviews of Torco for use in E46 M3 engines. Those engines have similar requirements to our engines and are far more finicky about oils. I just bought 10L of what BMW Motorsport uses in those engines, Elf Excelium 10W50.

Nightfly

I still believe that unless you're running your engine at the limit a whole lot, you're fine with what's in there at least until it gets real hot where you live. Even then, your car does have a cooling system, doesn't it?? So unless you're racing about, your oil should easily be within it's design limits. It's kind of sad to see another 'What oil is best' thread again. If there really was one 'best' oil, I'm sure that every single racing team would be using the same thing, just to protect their engines. Instead, what usually happens is they pour in whatever premium product is made by whoever is sponsoring them. If any of those products had lots of engine failures, I'm sure the other companies would point that out in their advertising. So far, that hasn't happened. Instead, what we get is idiotic things like 'look how long an engine can run without any oil left in it after we drained all of ours out'. So, as long as you keep the oil IN your engine, you should be alright, and so should your engine. If you're planning on going open road racing, and holding the revs to the max for extended periods, then maybe you should go ahead and change it. Oil is still pretty cheap. Other than other consumables, it is the cheapest thing we put into our cars.

Emickelsen

Damn, this is good stuff!

hacker-pschorr

Define "real hot".
I experimented with some lighter weight oil last summer, just putting around town my car was not happy (low to no oil pressure at idle, clacking lifters etc...). I'm in NE Wisconsin, most of the country is warmer than it is here.

Bill51sdr

I think the consensus here is... just top it off and show up at the damn karting event!!! See ya manana!

The_Remora

Lets see what MK has to say about this one, lol.

FlyingDog

Umm... I wouldn't consider that consensus. I wouldn't drive it unless I absolutely had to get somewhere. 10W30