there are many factors that come into play when addressing fuel mileage concerns. I always address the first things that I see, and disregard if you have done some of these check already, wheel and tire size and pressure: are they the factory size and is the pressure correct. The tire pressure spec is on the driver door jamb sticker. Second: Maintenance, air filter, oil and filter, spark plugs. Even if they seem good, they have an expiration date in regards to the miles on the vehicle. Third: Trouble codes in the power-train control module. Even though the service engine soon light is not on, There could be continuous memory trouble codes in the background. Fourth: turn on the vehicle and view the fuel trim pids (if you have a scanner with this capability), they should be within 10% of 0. They PCM will not set a code until the fuel trims exceed 15% for a calibrated amount of time. I replaced the intake gaskets on my daughter's corolla because the rubber gasket was hard as a rock and allowed unmetered air to enter the intake on a cold start-up. Your mileage is right at that point where these gaskets go bad fyi. If the thermostat has not been replaced yet, I would recommend doing that because a stuck open thermostat will leave the vehicle in closed loop operation, which is a fuel rich cold start operation. Just a few basic things for you to check, hope this helps!
Sep 23, 2019 at 9:57 AM
