I know the technology is better but I have a bad feeling about running anything thinner than a 30 weight. Why? Old habits I guess. But I wouldn't use super thin oil in a car I was going to beat on or a truck that was hauling but that's just me
First off, have you ever owned a vehicle that specified 5W-20 from the factory?
If yes, did you experience an engine failure directly related to the 5W-20 not providing enough protection, when the oil was changed at the manufactures recommended interval?
I'm going to bet the answer to both is no.
I'm going to double down on that bet by saying that this whole forum, the number of oil related failures for an engine that recommended 5W-20, and the owner changed the 5W-20 at the recommended intervals is less than 5.
This is for all different types of engines, and not just the Mustang engine in question.
5W-20 is good oil, for the engines that its recommended for.