I’ve heard that doing over 65 and going in reverse (not at the same time) uses more gas. Don’t know if thats true.
Find the cheapest gas in your area on gasbuddy.
The best gas saving tip (at least for your wallet) is get a ride. Or walk.
Always keep a lookout on the stretch of road ahead of you so you can plan ahead
Also a good idea to avoid any detours to the hospital (c’v)