[jpd80]

I've noticed that that a larger capacity atmo engine generally gives better economy when
towing than an Ecoboost engine which needs part throttle enrichment to avoid detonation.

Also, if Ford put an Ecoboost into a really heavy truck like a Super Duty, it would be
constantly under part throttle fuel enrichment and using a lot more fuel than a large V8.

A petrol V8 towing anything is always going to use plenty of fuel but with enough
basic capacity like say, a 5.0 litre may be enough to keep it away from rich mixtures
and mitigate the hit on fuel economy like the large Ram Gasoline Pick ups.