Help! Struggling to break 11 mpg

[hammonss]

I've got a 2015 Sierra crew cab, 5.3 liter. Driving mostly city miles, just rolled 1000. I'm not hard on the throttle, I've tried 87 and 89 octane. I even tried to drive as conservatively as possible to keep it in v4 as much as possible for an entire tank. Doesn't change, I get somewhere between 10.4 an 10.9 per tank. That's actually resetting the trip meter and calculating with actual fuel going in the tank. The last 25, 100, 400 reflect numbers pretty similar, maybe a little lower than I calculate, but real close.

 

Any thoughts? These numbers are nowhere near the estimates. Had I known this going in, if this is how it's going to be I never would have gone this route. MPG is one of the big reasons I went with the Sierra over the tundra.

 

Hope someone can help

[tw627x]

Where are you located and weather conditions?

[Bigmoore]

I get about the same up in Ohio with the colder weather, nothing to worry about. Was getting 17 to 20 mpg prior to winter.

[hammonss]

Northern indiana. It's bee -5 to +25 since I bought the truck about a month ago. Are we suggesting that cold weather drops the mpg by 40% ?

[Bigmoore]

For me yes, i also use remote start frequently too. That uses a lot more gas than you think. I have the same problems in my cars. about a 4 to 6 mpg drop.

[SouthpawHD]

I'm getting around 11-12 now. But I let my truck warm up for 10+ minutes most of the time because its been so cold during February and my commute is rather short.

 

When I got the truck in January, I was getting around 14-15.

[Bigmoore]

I typically get 15-17 in the city also normally. i usually drive on highway and backroads so its alittle higher in my case

[SouthpawHD]

Edit - double post.

[Bigmoore]

double post for me too

[TJay74]

Yes, cold weather along with winter gas, extended idle time and remote starts could easily drop fuel mileage by 40%. The colder it is outside the more fuel the ECM delivers since the air is denser. Add to that the other factors I mentioned at it will eat at your mileage pretty quick.

[pm26]

Stock GM tuning probably accounts for that bad fuel economy under cold conditions too.

Stock GM tuning probably accounts for that bad fuel economy under cold conditions.

[SouthernSilveradoGuy85]

I got an average of around 16-18 with mostly city driving and some interstate during the summer. Around here I get around 11.5-12 of all city driving with a little highway or interstate in the winter. I also have no problem getting 22 on the interstate in V8 mode in the summer but I can't hit 16 in the winter.

 

So yes, cold weather does effect mpg. It's not just from warming up either. Cold air is more dense which means the computer will adjust the air/fuel mixture by adding more fuel. It's also why back in the day you had to always adjust the carb, especially if you went to the mountains where higher up you go the less dense the air is. Sometimes depending on the setup you might can even feel the difference in acceleration between summer and winter by having better throttle response in the winter.

[hammonss]

That's pretty disheartening to hear. I've owned 2 4cyl turbos, 2 twin turbo v6s, a v6 4 runner with super charger, v6 fj cruiser, and a v6 sienna. Non of those have been affected by the air temperature like this. Someone mentioned the stock GM tune, has anyone had better success with an aftermarket tune? I mean in regards to MPG.

[fondupot]

If you are doing constant city stop and go with a lot of cold weather 11 mpg sounds about right

 

 

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[SouthernSilveradoGuy85]

That's pretty disheartening to hear. I've owned 2 4cyl turbos, 2 twin turbo v6s, a v6 4 runner with super charger, v6 fj cruiser, and a v6 sienna. Non of those have been affected by the air temperature like this. Someone mentioned the stock GM tune, has anyone had better success with an aftermarket tune? I mean in regards to MPG.

 

I don't know much about forced induction other than what I've read and all, but I would think a forced induction engine wouldn't be effected as much by cold weather since a turbo or supercharger already compresses the air so the air being more dense int he winter may not look to be as big of a difference. Then the 2 naturally aspirated V6s you've had use less air than a V8 so you won't see as much of a difference.

 

Science and physics, aren't they great lol.

 

 

I will admit though, it seems like this '14 is effected more than my 98 and 86 that I had. Maybe the '14 being direct injection has something to do with it. My 86 was carb and my 98 was FI but was sequential so the injectors put the gas in right above the valve opening while direct injection puts the gas in directly in the cylinder hints the name.