Are you seeing the pattern yet? Yep, anything that makes your engine work harder costs you fuel economy. Your transmission is no exception. Primarily I’m speaking of automatic transmissions, but you could also apply this to the manual transmission as well. If you have a manual transmission, this might not be your first check, but if you’re running out of options with a manual transmission vehicle, it’s definitely worth a look. This section mainly refers to the automatic transmission, however.
If you have poor fuel economy and an automatic transmission, checking the fluid level is one of those quick checks that can yield big results. If the fluid is low, discolored, or full of air bubbles, your transmission won’t work as efficiently. It might even start to slip, which can cost you MPG. If the fluid appears dark or old, you might consider changing the fluid. Just like changing your engine oil, this can help your fuel economy a great deal. While you’re at it, you might also consider changing the transmission filter if applicable. This will ensure that your automatic transmission is in top form and is as efficient as it can be. You can find more information about automatic transmissions in the Solving Transmission Problems article.