318 MAX fuel economy builds?

Any time you raise the compression you make the engine more efficient. Research expansion ratio. It’s a BIG deal.

But you have to be able to build a combination that is capable of the compression ratio you want and do it without making it miserable to tune or it’s so detonation sensitive you want to pull the pin on a grenade and drop it on the carb.

It can be a fine line there.
If that's the case I'd get a custom ground cam for a higher compression ratio but low enough lift and duration for efficiency. I'll research the expansion ratio as well I appreciate that info.