This is a recent topic from an MG site. The standard go-to grade in MGs and a lot of other old British cars for a long time has been 20W-50. The manuals list about a dozen different possible grades depending on expected operating conditions, but 20W-50 is the go-to all around grade. With concerns over ZDDP, many of us now have switched to oils specifically indicated to be high in it(Brad Penn, Amsoil, and VR-1 are all favorites) but that's another discussion/argument. Recently, there was a thread where someone's arguing that their mechanic is very adamant about how these "small engines" are "harmed" but oil as heavy as 20W-50, and that 10W-40 or lighter should be used instead. The member, BTW, is base out of Florida. Of course, a lot of less than charitable discussion has ensued, but I'm wondering what the thoughts on here are.