I have just increased my Miles per Tank by 40 ! yese that's 40 miles of my usual driving and in similar conditions etc......how I hear you ask........wel it's like this:-

Last service I asked for fully synthetic oil and the dealership in question used Castrol 20/60 (the prefeered oils by Subaru (that's what they said)). I complained syaing it was too thick and they ignored me say it is recommended by Subaru UK, so I know nothing.

I called Subaru UK and they agreed with me and said they recommend Shell Helix Ultra, fully Synthetic 5/40 I think that's what it was). So I suggested they inform the dealership again.

Anyway this service I asked again and they had both the Shell and the castrol and I chose the thinner Shell and that's what they have used.

Ergo, less friction and better miles per gallon by far, Whey hey !!
Slightly better performance and more miles per gallon, happy chappy !

 

most people on here prefer Motul though ......and we don't care about mileage lol

 

Send them a bill for the extra petrol you've used .....Oh and go somewhere else in future who know what they are talking about