Millers XFD 5w/40 fully synthetic for diesl engines that require that grade. It gets the API CH4 classification which is unique to Millers at this time, I think.
For cars I've again stuck with a fully synthetic oil but there's much more competition out there. Millers is up there with the best, but Mobil 1 is hard to fault. Even Halfords' own brand 5w/40 synthetic is a decent oil - manufactured by Esso.
I suggest that you dismiss mineral oils entirely, a good semi is a much better bet for just about any engine. Unless, of course, you're running some tasty 1940's machinery that really does burn some oil intentionally, then you need the good ole mother earth stuff |