To be honest, I don’t really feel that “tune up”’ is a term that applies to modern vehicles. A better term for modern vehicles is “service.” Back in the day, engine management systems were mostly mechanical. Therefore, you would do a periodic tune-up of the engine and its systems to get it to run efficiently. This might involve some adjustments as well as replacing some of the serviceable parts and filters.
These days, those adjustments are a thing of the past. In some ways, this makes things easier, as you don’t have to have the experience and tools necessary to perform a proper tune-up or service. Theoretically, the only thing you need to worry about on modern vehicles is purchasing quality parts and installing them correctly. That is sometimes easier said than done, but you get the point.
So, if you have an MPG problem and you’ve gone through the simple checks, it’s time to turn your attention to the serviceable parts on your vehicle. Most modern vehicles have a service interval, usually consisting of a list of checks accompanied by fluid and filter changes within a given mileage or time frame. See your owner’s manual or service manual for the service items and service interval for your vehicle. You can find more information on diagnosing and repairing performance problems in the Diagnosing Performance Issues article.