The 3.0 3VZFE from Toyota was always mocked as the “fuel efficiency of a V8, power of a 4 cyl”. The motor was a joke and the 5VZFE that came later was much improved.

Ford does decent with their V8 cars (they’ve had most issues with the 1.0, 1.5, and 2.7 ecoboosts), although the EPA ratings are tight. To get a good idea you’d have to compare equally, like finding another 5.0L, 480hp car that weighs 4,000 lbs (or at least that ballpark). they’re not terribly common.

I think the most common failure on a mod family V8 was either cam phasers or spark plugs. Which thankfully they fixed on the coyote. Other than that the car will die before the engine.

When I bought my 2016 mustang, I got 27.5 mpg on the trip home. I’ve averaged 30 before. They’re efficient if you stay under 3k rpm’s most of the time. City driving they’re ok, I get 18. Averaged over the life of the car I have got 24 mpg total. Which for a 3,800lb 435hp car is pretty damn good.

Throwing that Americans get bad mpg out of V8’s is a bit skewed. Gas is cheap here (relatively) and they’re mostly in trucks/suv’s and not cars. Like currently it’s $2.50/gallon at my Costco.

Not to mention, heavy duty “light trucks” like the F250 or GM2500 and up, do not have to adhere to any mileage standards and are exempt.