Car Maintenance Once it was considered good practice to let the car engine idle a minute or two following cold starts. Today with modern technology, the opposite is true. An engine operating under road conditions will warm up faster and run more efficiently than one that is idling.(46). When you have a full tank of gas, park the car facing downhill if possible; this will prevent any gas from coming out of the tank.(47). Your car will stay cooler, too, and that means less gas-eating work for the air conditioner once the engine is started. (48). Narrow-track tires produce less friction and thus less rolling resistance. The same effect is achieved by adding three to five pounds above the recommended pressure to each tire, without exceeding 32 p. s. i.; while this won't noticeably affect your car's riding quality, it will increase tire life and gas mileage. Check tire pressure often, especially when the weather turns cold.(49). This could Cost you two miles per gallon. Fuel-economy tests show that radial tires improve gas mileage. A car that gets 15 miles per gallon with conventional tires would get 16 miles per gallon with radials. Snow tires should be fixed no sooner than necessary and removed as soon as weather permits.(50),and you pay a one-to-three-mile-per-gallon loss when you have 'snows' on. A Stay away from popular widetrack tires if you want mileage