EMan 928

Not to start yet another oil thread, but one question.

New to me 89 911 Cab (84-89 variety) with 54k miles. Previous records show the owner using Mobile 15W-50 Synthetic oil for the car. Today I call my shop to schedule an oil change and he says no to synthetic and is suggesting Shell Rotella 15W-40 non-synthetic. He says these cars used conventional oil when they were new and no reason to go to synthetic..in fact, he said the Mobile 1 is too "thin" for these cars.

What do you guys think. With the engine using Mobile 1 for the last 16 years, is it a good idea to switch?

Thanks in advance,

LexVan

Buy your own oil, and deliver to the shop. Mobil 15W50, Mobil 20W50 Twin V, or Motul 300V, Brad Penn. Are all excellent aircooled selections.

theiceman

i have never been a mobil one fan but thats just my personal experience. i am sure they are all good products.
i stick with BP or Valvoline VR1 racing .

rstarga

I've used Mobil 1 15-50 in all my Porsches, 73S, 82 Turbo, 91 Turbo. Never had a problem, available just about everywhere. Probably put around 280k miles on all 3, hot weather, cold weather, long high speed trips and around town, over 38 years of using it, (since it came out).
Make sure it is 15-50.

P.S> I never go past 8k or 5 months between oil and filter replacement, whichever comes first.

spanky

I use a combination of M1 15/50 oil and M1 V twin 20/50 oil in the 911, 951, 240Z & 968. 50/50 mixture at every oil/ filter change. The V Twin 20/ 50 has the higher ZDDP levels that s needed in the older engines. I have been doing this for over 14 yrs and my engine seems very happy. I change the oil & filter in the 911, 951, 240Z every 2 yrs as I never put more than 4000/5000 miles on them per yr. The 968 oil is changed every yr The 2 BMW 's uses Shell Rotella 5/40 synthetic oil which is a great oil and I change it every yr.

rstarga

The 15-50 Mobil 1 already has enough ZDDP, the other weights do not. Is is specifically recommended for flat tappet cars.

spanky

^^^^I ues a blend just to be sure. M1 V twin has 1600 ppm vs 1200 ppm for reg 15/50 M1

myflat6

I have been using Brad Penn. seems to have consistent recommendations.

EMan 928

Thanks for the responses, everyone. So, the consensus says to keep the Mobile 1 or at least a synthetic oil. The shops recommendation to put non-synthetic is something you guys wouldn't do.

LexVan

Correct. Bring own oil. Or find new shop. Drop the "e" too.

Sent from my iPhone using Rennlist

rstarga

my recommendation is for Mobil 1 15-50, don't have knowledge or experience with other synthetics.

jcslocum

The Rotella is a good choice for older cars as it's now the latest spec of diesel oils that still has the good additives. We use it in our old Alfa and Mini. I use Brad Penn for the 911. You are looking to avoioi cam wear that is common when using the low zinc (ZDDP) oils of today.

EMan 928

What Brad Penn do you use? I'm using 20W50 in my 928. Same weight for the 911?

mpiffaretti

If the car was using conventional oil and then you go to a Full Synthetic oil, the molecules of the latter are smaller and therefore will make a car leak sometimes. It happened to me on my SC, and I regret having deviated from the conventional I was using.
Since your car is already using Synthetic, and if its not leaking, then there shouldn't be a reason not to continue to use the same oil if that is your preference. Porsche sells their own brand for your car and it is a Synthetic, they only make conventional for the pre 1974's. Your engine will be happy either way, just remember that the best oil is always clean oil..

TerrySmith

So I'm new to this whole ancient Porsche thing and the Indy guys that have looked at and changed oil on my '88 Cab have used Swepco 306 20W-50. The label does not say it's synthetic but does list all the cool stuff they put in it to make my engine last.

So is this a good one, or are the mechanics using it because it is cheap?