2015 Mileage drop

[rgould22]

When my truck was new I would average between 20-25 on the highway. Recently it has dropped to 15-20 on the highway. 58k on the odometer. Same gas. I hooked the truck up to a scanner on a computer and got interesting reading from one of the O2 sensors. It would bounce between .7v and 0v while the other sensor would stay at about .7v. (see picture bottom blue graph line) Is their anything that could cause this besides a bad O2 sensor? I plan on replacing the O2 sensors. 

 

[Brianibew]

What do your long term fuel trims look like?

[15 Z71]

My 15 is same way. I could get 23 mpg on highway when new also. Now I'm lucky to hit 19 or 20. 44,000 miles on it now. I guess the motor is getting older not new anymore. I still average 17 which I'm happy with. 

[SS502]

16 minutes ago, 15 Z71 said:

My 15 is same way. I could get 23 mpg on highway when new also. Now I'm lucky to hit 19 or 20. 44,000 miles on it now. I guess the motor is getting older not new anymore. I still average 17 which I'm happy with. 

I am NOT selling oil catch cans!! With that said, do you by chance run one? The thought is that over time, oil and contamination gets sucked into your combustion cycle through the intake valves. When the valves get "coking" the airflow is interrupted causing less efficient combustion and thus robbing you of some MPG. This would obviously get worse over time so it would make sense to see this as the miles get higher. Certainly not saying this is the cause but it could be part of it.

[15 Z71]

16 minutes ago, SS502 said:

I am NOT selling oil catch cans!! With that said, do you by chance run one? The thought is that over time, oil and contamination gets sucked into your combustion cycle through the intake valves. When the valves get "coking" the airflow is interrupted causing less efficient combustion and thus robbing you of some MPG. This would obviously get worse over time so it would make sense to see this as the miles get higher. Certainly not saying this is the cause but it could be part of it.

No catch can. I'm not sold on them alot of my friends have 14-18 gm trucks none of them have them either. Some have over 100,000 with out one.  I think a big part of it is I'm not is easy on the gas pedal as I was when it was new. Lol

[PMurray]

Cold climate area? Canmake a big difference this time of year. Fuel mix is different than in warm weather.

[Grumpy Bear]

Fairly specific question. I'm betting @1SLOW1500 has an answer or at least a direction. He does a fair amount of lap top tuning and will know what your readings mean....I hope....

 

He has a build thread or look him up in the directory. 

[chrispassas21]

Fairly specific question. I'm betting 1SLOW1500 has an answer or at least a direction. He does a fair amount of lap top tuning and will know what your readings mean....I hope....

 

He has a build thread or look him up in the directory. 

@1slow1500

 

 

2015 Silverado LT Midnight Edition

4.5” CST suspension lift

Sent from my iPhone using Tapatalk

[Loco-diablo]

I and a few other guys with trucks that I've talked to have noticed a drop in mileage just over the past few weeks! Coincidence? Or did they do something to the gas refinement that being shipped to the northeast?

Weird... 

[Olvim]

17 hours ago, PMurray said:

Cold climate area? Canmake a big difference this time of year. Fuel mix is different than in warm weather.

This. I’m from Michigan, and the winter gas mix along with temps hovering at or below 20 degrees, combined with fairly short average trips (15 mile drive to work) have seen my MPG drop from 19.5 combined to around 17. I drive a 2018 5.3L. I’m also a little heavier on the pedal than I was when I first got the truck. 

 

Nature of the beast here in the north, so I suppose it could be an O2 sensor or, depending on where you live, it might just be the climate. I was getting 24mpg on the highway in the summer! Summer blend and good temps help mileage a ton.