A 5w 30 would be fine if you lived in Norway or Alaska. 10w 50 is what's considered right for the 2.5 with the uk climate. I doubt a 5w 30 will cause you any problems especially in the cold weather and normal driving but i doubt it will give you the best protection for hard driving or a hot engine. As said by another poster in this thread, the 2.5 engine runs at least 10* hotter than the 2.0 engine hence the heavier grade oil. I always used a fully synth 5w 40 but when my engine was re-built (nothing to do with the oil) the engine builder told me not to run a 2.5 on anything less than a 10w 50.

 

Theres loads of choice for 5/30 full synth. There was a castrol edge 10/40 full synth but it said turbo diesel in big letters on which put me off ha ha.

 

Is 0 grade oil quite a new technology then with the companys trying to cover all bases?

 

I just looked in my hand book. it gives 5w 30 with an arrow pointing left towards cooler temps, then the arrow pointing right towards hotter temps and the grades 5w 40, 10w 40 and 10w 50. On the other page 11/16 it says use API sm rated 5w 30 "Energy saving". I think there recommending the 5w 30 because it takes less energy to move a lighter oil around your engine so will do more mpg and make the car appear greener. Any extra wear caused due to lighter oils in a hot engine will be over the long term. I doubt Subaru will lose sleep over that. Just means they may get to sell you parts or a new car at a later date.

 

Will defo be moving up grades when I change the oil again, but Will report back if I have any trouble in the mean time.

 

Well i returned it and got 5/40 castrol edge. Sweet

 

The climate here over the past few months has been like Alaska, used 5-30 last time but will change it again when we start to head toward the warmer weather in August it may get up till 10 or 12 by then

 

Have been thinking it is time to change my oil (3000 miles)

i have been using Magnatec 10w-40 part synthetic so
good time to buy £20 for 4 litres