38% in the Toyota atkinson cycle engines, which are the top of the industry. Typical is more like 28% for gasoline engines. Then you have automatic transmission efficiency, which is at best ~%80, so now you're down to 30% at best.
More typical: 28% engine thermal efficiency, 75% transmission efficiency means 21% overall efficiency.
So yes, gasoline energy equivalency is pretty meaningless unless you multiply it by 0.2 first.
Gas mileage figures from the EPA and others don't account at all for the time a vehicle spends idling before/after a trip - or even in heavy traffic, just waiting at traffic lights. For example, time parents spend sitting in their cars idling waiting to pick up their kids, time spend idling in coffee and fast food drive-through lines, etc. Start-stop systems help, but a lot of people disable them.
More typical: 28% engine thermal efficiency, 75% transmission efficiency means 21% overall efficiency.
So yes, gasoline energy equivalency is pretty meaningless unless you multiply it by 0.2 first.
Gas mileage figures from the EPA and others don't account at all for the time a vehicle spends idling before/after a trip - or even in heavy traffic, just waiting at traffic lights. For example, time parents spend sitting in their cars idling waiting to pick up their kids, time spend idling in coffee and fast food drive-through lines, etc. Start-stop systems help, but a lot of people disable them.