I feel sorry for Daryl, I just filled up this week for $3.62/gal for 87 octane, and I'm still complaining about it.
When gas prices go up everyone starts questioning their need for economy vs power.
The cam selection will affect MPG much more than the gears. This is why the newer engines with cam phasers can produce so much power and still achieve good mileage.
The cam phasers are good but after owning one for a while, the Honda VTEC is definitely the coolest way I've seen this done. It has two completely different cam profiles that engage at higher RPM and high power engagement. This allows for both increased duration and valve event timing changes only when needed.
This isn't really new knowledge. Manufactures were getting really good mileage in the '70s at the sacrifice of power:
https://www.ford-trucks.com/articles/throwback-thursday-1976-f-100-50l-got-better-mpg-than-2015/ What's changed is they've learned how to engineer and manufacture engines that can do both.
More commonly known is the inverse relation between displacement and economy. This is because a large engine doing the work of maintaining cruising speed is at a very low throttle compared to a small engine doing the same work. The large engine will have a higher vacuum and be working against that, wasting energy.
So when you want more power with older technology engines without sacrificing MPG, think turbo before cam and stroker kits.