Fuel mileage drop

Hi All new here have had several Tacomas, My 2019 SR 4x2 recently has been experiencing 3 to 4 mpg less that previously recorded. It dropped suuddenly in december 2024 at around 52k, Has new air filter 0w20 amsoil in the engine, since i've had the truck this happened suddenly, no check engine light, good performance and drivability. Anyone having the same issues? Ideas?
Thanks HalJ

 

Welcome to TW.
Same issue every year around that time (see below). Winter fuel mix, driving habits, warm-up period, etc.

 

how has the daily average temperature changed? Longer warm-up times = more gas used. Cooler temps = more gas used (as engine is more efficient as air is denser = more gas is required)

 

Well Thanks for the reply and graph. This didn't happen last winter, don't let it warm up for mor than several minutes do this even in the summer, possibly winter fuel but just seems odd that it happened like some one turned a switch., probably keep an eye on it and see what happens in the spring. just seemed odd

 

Where are you located?

Even while driving around, it takes much longer to warm the engine up. When your vehicle is sitting still it takes much longer to warm up, then if it is under load. honestly it should go back to normal once it's about 70F consistently. if that doesn't happen, look into it.

 

well i'm in connecticut and have noticed thi while driving both locally and on the hi way for my 24 mile commute to work...all gages and eng temp are normal
thanks

 

Cold air is also denser so requires more effort to essentially push thru.

 

As am I. You can compare to the chart showing my experience.
If you pay attention to the instantaneous MPGs you can discern when the drive train has warmed up to optimum (acceptable) fuel economy. For me, it's about 4 miles at 55 MPH at 30°F. On a flat road at 55 MPH the instantaneous MPGs will jump to close to 30 once it reaches the most efficient operating temperature.
This Winter's numbers are skewed because of the extreme temps and my desire to thaw out my fingers in a stationary warm idling Taco cab.