I serviced my wifes 2005 3.0 R Spec B legacy which has a H6 boxer engine fitted.

I asked her to send me the detail of grade of oil to be used - ie viscosity. I bought oil from my local motor factors of the correct viscosity, but have noted on the container that its ACEA specification is C3.

I was looking for something else in the service manual for her car today and notice that it states use oil of ACEA B3 specification only.

I know that the oil I bought is intended for extended service intervals, that is not why I bought it, it will be changed at the usual 10,000 miles.

Is it possible that ACEA C3 oil did not exist in 2005 when the manual was produced therefore it was not prohibiting its use, because the spec was non-existent or are there additives either absent or present in the oil I have used which will have a detrimental effect on the engine. Happy to ditch £90 worth of oil rather than cause engine damage.

 

It will be absolutely fine. ACEA C spec relates to modern diesel engines as they are low ash to prevent the diesel particulate filters from blocking, but they are also fine for petrol engines and are generally good quality oils.