Used coventional 5w30 in Explorer 4.0 and conventional 10w-40 Jetta 2.Slo without issue and both ran well.
Tried synthetic 5w30 in Silverado 5.3 and was louder and noisier than anything else I've run thru the Silverado. Not a huge difference, but a difference was there. Also experience a very short but very loud lifter rapping with going from high revs to idle towards the end of a 5000 mile OCI. Coincidence, I do not know, but I'll not try again in the Chevy. As far as the others, the next OCI on the Jetta will likely be a Peak 5w30/10w-40 blend for the winter.