Here are a few ways to save on gas over Memorial Day weekend: Fill up now, because prices are expected to peak tomorrow. Use an app like GasBuddy to find the cheapest gas stations along your route. Paying with cash can save you 10 to 15 cents a gallon at a lot of places. And make sure your tires are properly inflated. It can save you over 10 cents a gallon, but 80% of us don’t have them at the right P.S.I.