Engine braking and mpg

2008 Tacoma TRD off road, V6, auto with towing package.

Did my first transmission flush at 102k by Toyota Dealer in Havasu City. Next two tanks of gas my mpg was down by 25% and am trying to figure out why. I monitor tire pressure a lot and it has not changed. Type of roads and driving has not changed. Every day a couple miles around town, about 10 miles on Highway 95 doing 50-60 mph and a couple miles off road to a campsite on BLM land. Another thing that has not changed is I do engine braking a lot when I approach a stop because I have a heavy camper in the back -camper is on full time. I shift to 3rd at 50 mph and then to 2nd at 40 mph. Have not downshifted to first at all lately. I don't think the flush impacted mpg, but could it?

 

Maybe the switch to winter gas? Still shouldn't be a 25% difference in mileage though.

 

I wouldn't panic over 2 tanks of gas. Give it some more time. I've seen fuel mileage fluctuate like that for reasons that can be hard to explain. It could be the gas you bought, or other factors. Sometimes you get gas the truck just doesn't like. It could old or contaminated. I'd try buying from a different source.

I've seen a high of 23 mpg and a low of 16 mpg on different tanks on the same day. Of course I drove 950 miles that day and conditions were somewhat different. But over the course of that 5000+mile road trip the overall average still hit 20.0 which is very typical.

 

Never heard of a transmission flush to cause poor mpg but anything is possible. Using the wrong fluid or not enough fluid, maybe.

My bet is on winter gas and/or idling to warm truck.

Also, are you down shifting your auto?

 

I had the tranny flushed and did not notice any difference. Definitely a mpg hit with winter gas. Buying gas in Yuma for Xmas.
Ho ho ho.

 

Have you cleaned your MAF ? My mileage is horrible and I suspect a dirty MAF . It’s on my list ! I’m 2008 also 127000 miles and have never cleaned the MAF

 

You're right! and add the fact the temperature is colder now can and will lead to lower gas mileage....Check your air pressure in you tires just to make sure that one is checked as well. Good luck