I know some recommend Quaker State Ultimate Durability 0W-20 Full Synthetic Motor Oil, which apparently has the lowest kinematic viscosity, if you care about that kind of thing (prob more so on the hypermiling side). If I did my own changes, I'd prob go with that. It even beats out ...
Yup, the cat. Most manufacturer specified oils are good for cats and recently mileage and not good for the engine. Look at the latest oil standards - SN, etc. The is the crap ford is using 0W20! Obviously 10W60 is not MPG focused oil, the M division has a say here. But that is...