Decrease in fuel economy after 10K dealer service

Hand calcs and on-board mpg meter are showing a consistent trend.

17 mpg average tanks before service and 15 mpg average tanks after service. Service was 5 weeks ago.

I saw a mpg increase after swapping my CPS. Did they swap in another CPS? I don't want to ask them about this for various reasons.

Has anyone else experienced this?

 

Winter fuel has definitely hit me in the last few weeks. Could be that, or they reset your truck and it will need to relearn.
Maybe see if they did anything special during the service that could have affected your mileage. I'd just call and ask and if they ask why, just tell them your mpg have taken a hit since it was in.

 

Winter fuel + cooler, denser air (resulting in a slightly richer mix) = reduce MPG.

Nothing to do with 10k service

 

What’s your location? Alaska or florida or somewhere in between or elsewhere?

As stated the winter blend and cold air if applicable are most likely the culprit. My mpg’s have def. taken a hit the last month or so as well.

 

I live in SF Bay Area.
It hasn't been much colder 75 on average here

 

Same thing here. Down to 21-22 from 24ish.

 

How the heck is your MPG average that low? I'm getting 21-23mpg.

 

Manual

 

My last tank was a shit 15.92 mpg calculated at the pump. 16 mpg even on the dash. I commute into Philly area but live in the suburbs with an 18 mile commute, I have an auto 2017 TRD Off Road.

Granted I drove it like I stole it that tank as was late to work a couple days. I try not to use the heater or AC unless I have to.

My lifetime average seems to hang around mid to high 17’s though and my best was 18 ...Not the greatest but whatever.

Edit: back a couple months ago I could easily get 20-22 or so mpg per drive into work (not tank avg but trip commute avg) on the dash. It has to be the weather and the frickin winter gas.

 

Well damn. Maybe someone local can interject , I have no clue if San Fran has winter blend or where the north/ south cutoff is if there is one for winter blend.

 

Agree. Here in Michigan I’ve gone from 19.3 +/- 0.2 mpg down about 1.0 mpg as temps dropped from 80-90 degrees down to the 45-55 degree range. Have about 8700 miles on a 6MT.
Usually see a smaller drop as we head down in to the 20’s with other vehicles but every one of them took the most noticeable hit in the fall.

We also see more ethanol in the winter too but I’ve not been able to pin any #’s on that.

 

Maybe that's your problem? I've never had a tank under 18mpg, including towing a loaded trailer for over a tank.

 

If the wrong weight of oil was put into the engine during the service, eg 5w30, this could decrease your fuel efficiency immediately. Thats the only that would make sense to me.

 

I normally drive pretty gentle so my 17-18 mpg per tank thus far seems about right and on par with what everyone else is getting..


And the driving it real hard was only for Few drives into work. Granted I’m sure it didn’t help, but it didn’t kill my mpg like I thought it would have surprisingly. Granted I don’t think it can get much much worse than that. Haha.

 

Winter blend is sold everywhere... even the left coast. Even in places that don't get cold. Every year in October it switches. I posted a big long post explaining it last week or so.

 

Makes sense.