Hi all -

I recently saw 5w-40 castrol syntec (fully synthetic) in autozone - and on the back it says "made in belgium". Now, I know its probably not as good as the G.C. stuff, but is it better than say, 10w30 mobil 1? I still lose a little oil with the mobil 1.

Also, Ive been using 10w-30 mobil 1 for the last 2 oil changes, would it be detrimental to change to a 5w-40 oil?

I have a 2004 WRX.

The "good" Castrol is supposed to be made in Germany. Don't know about this Belgium stuff, but try it out. Swap oils willy nilly, your car or engine don't care. Mobil's stuff tends to be on the thin side of their weights so try another brand and see what happens.

The Belgian Castrol 5w-40 isn't as well loved as the German Castrol over on the BITOG forums. Most folks feel it's mostly group III, thus not as good as the excellent GC. If I was looking to run a 5w-40 in my STi, I'd go with Mobil 1 T&SUV 5w-40...an excellent oil for the money ($20 for a 5 quart jug at Wal-Mart).