Oil breaks down under use and won't lubricate, cool, or protect as well. A poorly tuned engine can increase fuel consumption by up to 50 percent or more. And a well-tuned engine minimizes engine wear.
Warm tires give an inaccurate reading because heat build up increases tire pressure during use.
Under inflated tires wear faster, waste fuel and are unsafe. Keep your tires inflated to the pressure specified by the vehicle manufacturer. Idling consumes fuel. Fifteen seconds of idling can use up more fuel than restarting the engine. Turn off the ignition if you are waiting for someone.