Only playing Devil's Advocate, but just because Prodrive use a 0W-40 oil in their WRC's doesn't necessarily mean it's right for a standard car - the pistons, crank, bearings etc. are different and running clearances are likely much tighter, hence the need for a thinner oil.

Having said that I'm sure both are fine, just I'm an engineer in the oil industry and ex-engine builder (though not with tremendous success !) so am just trying to point out that viscosity is one of many critical properties and shouldn't be overlooked.

Russ

 

Russell.

If you read all postings prior to this, you will see, that most points have been brought out, and analysed.

This was merely a conclusion reached based on the theoretical merits of all of the relevant technical postings.

Read all of the postings and THEN Colins and it will make more sense, (well it did to me).

Mike.

 

ANY OIL WILL DO AS LONG AS YOU REMEMBER TO PUT A SQUIRT OF FAIRY LIQUID IN EVERY SUNDAY MORNING AT ABOUT 6.30 AM
IT REALLY HELPS THE GEARS SLIP IN AND OUT NICE AND EASY AND WHEN IT COMES TO REBUILD TIME THE FITTER WON'T GET DIRTY HANDS.
WARNING-DO NOT USE A CHEAP BRAND BUT WHY DON'T WE ALL EXPERIMENT AND POST THE MOST FACINATING RESULTS ON THIS PAGE

 

Hmmm...the pressures obviously getting to you Justy. Must have been that comment about your broken caps lock key. Keyboards are pretty cheap nowadays - in fact less than the difference in cost between Mobil 1 and Shell Helix Semi. Which reminds me - what do you use in your grey import? Anyway back to the debate. The only thing I currently have to add follows on from Russell's comments - and that is, as the Impreza's turbo engine runs rather hot, then the clearances at cold start are likely to be quite large (re: heat expansion) - therefore perhaps requiring a thicker oil.

Also I've noticed in my Owner's Manual that it says that 0W..30 is not recommended for sustained high speed driving - implying it's OK for low speed gentle driving which of course includes starting the car (i.e. cold start)! Anyway I've hedged by bets and used 5W..40 fully synthetic (Esso stuff).

 

Justy.

There's no chance of any of your fitters getting their hands dirty really is there?

Most of the Imprezas in this country have been made out of bounds to you by your masters.

Still it's some peoples job to serve and others to be served I suppose.

 

Mail recently received on the IWOC.......

From: "Don Piper" <cipfa.vw@virgin.net>

message from Subaru technical service ( I happened to stumble across) From
John Baker no 1-1B-015 27/1/99

Subaru UK technical department have recently been receiving a large number
of queries from both the Subaru dealer Network and Subaru Turbo owners,
relating to the use of Mobil 1 0w-40w engine oil and the companies official
policy regarding its use in our 2.0 Turbo engine.
The only engine oil specifications we would recommend for use in the 2.0
Turbo engine are oil grade APIclassification SG, SJ, SH, SAE viscosity
10w-30, 10w-40. Using a SAE 5w-30w or lower viscosity for the Turbo models
is not recommended, as stated on page 10-14,10-15 of the Impreza owners
handbook A1790GE page 10-14, 10-15.

So their you are , if all else fails RTFM.

Hope this assists, oils were getting boring!

Second mail also received ..........

I have just been talking to Power Engineering who are going to give my car
its first service and they have recommended the use of Mobil one 15-50W as
they say that they have found the others too thin for the cosworths they
have dealt with in the past.

I then went to Mobil's web site and found this statement about 15-50W

http://www.mobil.com/oneracing/about/products/engineoil/15w_50/index.html

"15W-50 is perfect for hot-running or heavily loaded vehicles and special
high tech imported cars"

And as we dont get very cold conditions in the UK which is where a lower
rated oil such as 0W-30 comes in then I think this is certainly the right
oil to have in the car over summer.

..............................