Since November my mileage has gone down noticeably. Seemed to get worse in cold weather. Last spring I had replaced the plugs and changed the t-stat and coolant. It runs at what seems to be the right temperature and runs strong, just seems to get poor mileage compared to what it used to get.

Went from around 14l/100km on the highway and 15 in town to a consistent 18, doesn't really matter if it's in town or on the highway. It was a solid 22L/100km on my hunting trip when it was -30C, didn't matter if I was cruising the highway at 100kmh or pushing it down a gravel road at 130.

Air filter is new, cleaned the MAF, I recently switched back to running 91 octane with the SCT canned tune. Even took off my 33's and put the stock size back on with no difference. Brakes are not dragging and it doesn't make any weird noises, just uses more fuel. I'm wondering if the O2 sensors are starting to fail but haven't thrown a code yet or perhaps the temp sensor even though the gauge shows hot and it blows hot air pretty quick after a cold start.

Something has changed or isn't working as good as it used to but I have no codes to point me in the right direction, the shop I go to figured it was maybe fuel or the bigger tires neither excuse of which I buy into. any ideas?

 

My best guess would me 02 sensors and or poor quality gas, especially if you went back to factory wheel / tire size. You haven't changed your driving habits lately have you? Just asking..

 

Is the SCT still set to the 33"s?

Wayne

 

Good point bro..missed the tune

 

It could be something to do with the winter blend fuel. I've read stories where guys get worse mileage in the winter then summer due to the additives they put in fuel for the cold winter. I am hoping that is the reason for the terrible mileage I am getting from my truck.

 

Nope, changed back to 32's

 

check injectors

 

Winter blend fuel always decreases performance and mileage. It is supposed to lower emissions. Now that it is spring, the refineries should go back to a warm weather blend. Fuel blends vary by area.

 

I know here in Eastern Canada, I have to startup the truck I the mornings because it's been soooo cold. I notice in my EB, the mileage has gone down this winter as well. If the truck is running for 15-20mins each morning, would that still have an effect on overall L/KM even though your not driving wile its sitting in the yard warming Up? Just a thought. I too am hoping my mileage increases as spring and summer are soon upon us. I've had the same issue all wintered I just put bigger tires on two weeks ago, so it's not that.

 

Engines perform more efficiently at the correct internal temps. Warmer air is less dense so you will lose power but realize better mpg. Conversely in colder air temps, you will gain power but realize lesser mpg. Then add in winter fuel changes and VOILA...decreased mpg.
1) Try getting warmer engine air into your intake (block off any cold air access).
2) Block off some or most or your radiator from the colder outside air (you cn even try cardboard first)