Lowered mpg after dealer visit

so I took my truck in for 15k mile maintenance. After I got my truck back, I noticed my mpg were dropping down to 11-13 mpg average. I normally average 18-20mpg. It’s my daily driver and nothing has changed from before I dropped it off at the dealership. When I refueled yesterday, today I’m back up to averaging 18-20. We had a small cold front last week but I don’t think it should affect my mpg that bad? Anyone have any experience with this?

 

Do you still have tread on the rear tires after picking it up?

 

Everything looks normal. I thought the mpg were a fluke at first but I drove it an entire week averaging 13 at best. I had to fill up at 220 miles in and I got 16 gallons during fill up. Doing the math that average is 13.75mpg for the tank.

 

Maybe a trans reflash so it had to relearn your driving.

 

I've had the same thing happen as well. But I have a dash cam running all the time so I went in for review and found that it was just idling for well over an hour going nowhere (0 MPG) while waiting on the car wash at the dealer (one car at a time, moves manually from what I can tell). So on the next visits I just tell them to skip the wash as I can just do it myself.

Also noticed they turned my stereo waaay up testing out my OEM Audio Plus setup I suppose. But I didn't haggle them over it as they seemed to be having a good time and it was some good music my iPod was already playing

But that was just that tank avg.

However, I've noticed I've been getting around 15 MPG myself rather than my usual 17 lately, but it has cooled down a bit here. Not sure what's up with that, but I did have one trip do 18 so it's not all the time. Hard to say sometimes.

 

Even if they idled it shouldn’t reflect my daily trip average per drive. Like every time you turn off the truck the screen pops up telling you your trip mpg average and distance travelled. Every trip for an entire week I was averaging 11-13 per drive and i take the same route to work every day with traffic not being too different day to day.

 

Most likely, the porter that took you car left the engine running in the overflow parking lot until a service bay was open for a mechanic to work on your truck. It might have been idling for 20-30 minutes causing your MPG to go down.

One time when I took my truck in for service, I left my cell phone in the truck, so they told me it was ok to go to the back to get it. When I went back there, I saw a porter move one car to get access to another car. He left that car running, while he delivered the other car to the customer. After he delivered the customer car, I saw him jump in the shuttle bus to drive another customer home... who knows how long that car was left idling in the back parking lot.

 

I’m referring to continued low mpg output for the entire week of driving. Not just for that day the dealer had it.

 

Do you have an itemized service invoice? That might shed some light?

Should have been a tire rotation and that's about it. Did you feel a difference in your e-brake take-up (i.e. how many clicks). Maybe they adjusted the rear shoes and got them too tight?

 

I bet they re-flashed the trans and it is re-learning. Give it about 600 miles and you should be back to normal

 

i also noticed a drop for the first couple tanks after my 10k service...i usually average 17.9....idk how you guys are getting 20mpg....i feel like i baby the thing as much as possible already

 

possibly a combo of winter gas and reflash?

 

Looks like you got 20 MPG average in August according to fuelly. Wind, rain, snow, and winter formulation of gas all bring things down during this time of year.

 

Some dealers update to the latest software release every time the truck comes in. My dealer updated the software on my 5000 mile visit without me asking. Then at 10k miles I asked they update again to 04B03 which is the latest version.

 

Tire pressures drop when the temps drop.

 

Are you guys calculating your mpg or going off the lying computer? The 22ish tank averages are not close to the 17mpg reality.

 

Cold makes a huge difference especially on short trips from cold. The transmission won’t shift up into 6th until it hits a certain trans temp which affects your mileage. The engine doesn’t run as efficiently when cold.

With the OP in Texas I can’t comment on his local weather and temps so don’t know if this has any effect on him at the moment.

 

How is it lying? My truck tells me I get 16 mpg and fuelly tells me I get 16mpg. Before my tire upgrade I averaged in the high 18s but most was in town driving.

 

Do the cold temps require more air?

 

I had the same problem after my 5K service and I have a 6MT. I was getting 19-20 mpg and after the service I had to struggle just to get 17. I was trying to figure out what to say when I took it back. I can't think of what would have caused it. After a couple of tanks it's back to normal though.