So I usually fill up my tank after I go 300 miles on it, which turns out to be just under 30mpg usually. But I'm at just over 300 miles and found out that I am running low on gas because I let my girlfriend drive my car for an hour so she can practice stick. I really don't want to run out of gas and couldn't get it before work, and I need to make it back home (there's a really cheap gas station right by my house). What speed on the highway should I maintain to get the gas mileage? I know I should stay under 70mph, but there was this tour bus going 75mph and I was drafting right behind him to save gas. I figured I was so close to him that I was getting over 50mpg, but I'm not really sure how that stuff works. But my car felt much more powerful behind the bus when I accelerated, it was great! So is it worth it to go slower to conserve gas or to draft behind a huge truck??