When I take my car to Audi for the free oil changes they use Castrol (I am guessing 5w-40, as it is the approved Audi oil). However, when I change my own oil (can't wait 10,000 miles). I use Mobil 1 0w-40 (can't find Castrol 5w-40 at either of the auto stores in Annapolis). So on to my question - Is it a bad thing to change oil brand and weight?

Thanks

 

I've never heard of any problems, but if it were me I would stick to one or the other.