Oil Grade

[johnmaddox]

I have a 2007 gen 1 Cayman 3.4S and I am confused regarding oil grade to use. Mobil 1 0-40 seems to be the factory fill but those frightened by the bore scoring risk suggest using 5-40 grade as it is thicker and hopefully protecting the bore a bit more.

I always thought that the first number in the grade was the viscosity when cold - the lower the number the thinner when cold and circulates quicker in a cold engine.

The second number I thought was the viscosity when hot - the higher the number the thicker when hot.

In the context of bore scoring which tends to happen when the engine is very hot and put under heavy load then a 5-50 oil or even a 10-60 competition oil would seem to be a better bet.

Can someone help on grade to use to minimise bore scoring risk. I am not wanting a huge discussion on make of oil to use but just the grade issue.

Thanks.

[Trev450]

Hartech recommend 5w/40 for new engines and 5w/50 once run in.

[Ape50]

If 5/40 or 5/50 is better for the engine why wouldn't Porsche recommend / use it ? Sorry if this is a dumb question.

[Ape50]

...

Edited by Ape50 on Thursday 20th August 16:35

[Oso]

Porsche A40 approved spec includes 5w-40 and 5w-50 as well as 0w-40.

These formulations are all blends of oils of different viscosity grades. The idea is the lighter oils give protection when the engine is cold and the heavier oil would be too thick, and the heavier oils when the engine is warm and the lighter oils would be too thin.

The first number above refers to the viscosity of the lighter oils in the blend. Ow is very light - great for cold start protection but tends to burn off more easily when the engine is hot.

5w-40 and 5w-50 are fine as long as the temperature is above -25C - 0w-40 is for all temperature ranges which is why that comes from the factory.

So in the UK you are fine (and arguably better) with the 5w-40 or 5w-50 (edit: unless you live in in the cold depths of Scotland or drive to the alps in winter! - I have friends in Arizona who run 5w-50 in the summer when it's regularly over 40 degrees and then change to 0w-40 in the winter to go ski-ing e.g. for ski trips to Colorado).

Top tips if your car is a keeper - change your oil every 12 months or 10k miles. Use the best synthetic oil you can buy. Keep it fully topped up.

Edited by Oso on Thursday 20th August 17:14

[Oso]

I wrote to Hartech and asked them to look at this thread - I think it's a very interesting question and I'd appreciate hearing their thoughts and the thinking behind their recommendations (which for their rebuilt engines are here in the second paragraph under 'Labour'):

http://www.hartech.org/porsche_996_997_Boxster_eng...

[YoungMD]

Yes I wondered about this after getting my 997.1 wanted to top up oil but didn't know which oil to used, called the last Indy who serviced it and they said they use 10-40w mobile s2000 after cars are 5 years old. There explanation was that after a bit of wear 0w synthetic is too thin.......as I am a bit of an engineer and sad I did loads of research, seems loads of conflicting chit chat, in the end I used Millers 5-40w, but seems different people say different things

[johnmaddox]

Very interesting to hear the views so far. Thanks.

[Rockster]

YoungMD said:

Yes I wondered about this after getting my 997.1 wanted to top up oil but didn't know which oil to used, called the last Indy who serviced it and they said they use 10-40w mobile s2000 after cars are 5 years old. There explanation was that after a bit of wear 0w synthetic is too thin.......as I am a bit of an engineer and sad I did loads of research, seems loads of conflicting chit chat, in the end I used Millers 5-40w, but seems different people say different things

Gee don't let my 2003 Turbo with 135K+ miles on its engine or my 2002 Boxster with 293K miles on its engine hear that.

They are both fine with 0w-40 even in pretty high ambient temperatures (116F one day in the Boxster, 118F when I was in the Turbo) but since it doesn't get that cold here (hardly every below 32F even on the coldest days (or nights)) and yet gets pretty hot (100F+ once in a while in the summer) I switched to 5w-50 oil just because it seemed like the right thing to do. But one in a while 0w-40 gets used when 5w-50 is not available and the engines are fine.

No 10w-XX oil is a Porsche approved oil and for this reason I would not use it. I would not use a shop that uses it either.

Oh I don't run any oil more than 5K miles.

[evojam]

I run 5w40 Fuch Titan Pro race-S in my Boxster 2.7 changed every 5000 miles.Best oil I've tried.

[Shaoxter]

evojam said:

I run 5w40 Fuch Titan Pro race-S in my Boxster 2.7 changed every 5000 miles.Best oil I've tried.

Could you elaborate on how you can tell one oil is better than another?

[evojam]

Shaoxter said:

evojam said:

I run 5w40 Fuch Titan Pro race-S in my Boxster 2.7 changed every 5000 miles.Best oil I've tried.

Could you elaborate on how you can tell one oil is better than another?

I'm no oil expert but I trust my ears,tried a few different brands and using the car everyday plus long jaunts abroad and getting very tuned in with how the engine sounds from both cold startup and baking hot after a good thrashing I reckon this stuff makes the engine a little smoother all round.Not saying it's better than another brand,just personal experience..

[Klippie]

The Oil Lab, I had them check a sample from my car at its first major service and the results showed there was plenty life left in the oil and nothing of concern with contaminates, this will be done at every major service from now on to keep an eye on the engines condition.

I'll keep using Mobil 1 0w-40 and change it at the recommended interval.