Gas Buddy (Free)-- Find the cheapest gas on the go for iphone, app and all mobile devices.
GasBuddy shows you a map with each station represented by an icon and price (For iPhone, Android, Windows Phone and Blackberry)
Local Gas Prices (Free) -- Local Gas Prices provides the latest information for helping you save money at gas stations across the United States. You will find the cheapest prices in your local area for regular, plus, premium, and diesel grades. (For iPhone)
Cheap Gas (Free) -- Find the cheapest gasoline nearest to where you are! Then, map a route to where the cheap gas is.(For iPhone)
AAA TripTik Mobile (Free) -- Shows gas station locations and provides current fuel prices for road trips (For iPhone and Android)
Fuel Finder ($2.99) -- Helps you find the cheapest gas prices in the US and Canada. It lists gas stations based on price and distance. Has calculator to determine annual savings. (For iPhone)
Tips to Improve Your Gas Mileage
Drive sensibly: Aggressive driving (speeding, rapid acceleration and braking) wastes gas. It can lower your gas mileage by 33 percent at highway speeds and by 5 percent around town.
Observe the Speed Limit: While each vehicle reaches its optimal fuel economy at a different speed (or range of speeds), gas mileage usually decreases rapidly at speeds above 60 mph.
Remove Excess Weight: Avoid keeping unnecessary items in your vehicle, especially heavy ones. An extra 100 pounds in your vehicle could reduce your MPG by up to 2%. The reduction is based on the percentage of extra weight relative to the vehicle's weight and affects smaller vehicles more than larger ones.
Avoid Excessive Idling: Idling gets 0 miles per gallon. Cars with larger engines typically waste more gas at idle than do cars with smaller engines.
Use Cruise Control: Using cruise control on the highway helps you maintain a constant speed and, in most cases, will save gas.
Use Overdrive Gears: When you use overdrive gearing, your car's engine speed goes down. This saves gas and reduces engine wear.