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Fuel issues.

Birk01

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Burlington Kansas
I have a 2020 chevy trail boss with 40k miles on it. I bought it with 23k so second owner. Anywho I noticed a huge drop in fuel mileage 2 oil changes ago. Was averaging 17 to 18 mpg but now I'm at 10 to 11 mpg. I've switched fuel, where I have purchased fuel, I'm also driving about the same speeds everyday. I haven't done pen and paper yet I was just going off by my monitor/dash screen. Even if it's not right I can tell my fuel mileage has gone down. I do usually put 87 in it but if I was getting the good mileage with it why all of the sudden drop? No codes nothing seems wrong it drives great and throttle response is solid. Any insight would be greatly appreciated!
 
Any ethanol in the fuel you are using? It'll lessen your range over 100% gasoline... (E85 = 25% less MPG)
Other changes? Bigger tires? Lift?
If not, maybe hook up a scanner and check the long term fuel trim for too rich, but not significant enough to set a code. If you have a vacuum leak or other situation causing the computer to see lean, it will add fuel, within the parameters of its programming, to compensate and MPG will suffer.
 
Any ethanol in the fuel you are using? It'll lessen your range over 100% gasoline... (E85 = 25% less MPG)
Other changes? Bigger tires? Lift?
If not, maybe hook up a scanner and check the long term fuel trim for too rich, but not significant enough to set a code. If you have a vacuum leak or other situation causing the computer to see lean, it will add fuel, within the parameters of its programming, to compensate and MPG will suffer.
I agree. If your truck is chipped (after market) some of the companies offer a pigtail that you Bluetooth to your phone and app. It works very nice as you can watch and historically look at saved maps. I like it. I have a 2021 with 34K on it now and being chipped, lifted and big tires I still get 19-21 on flat ground. Off road, yeah don't care. 😂 If you lived closer I'd look at it. You shouldn't see a drop in mpg like that. Highly unlikely as you would get a warning or smell of a sieged brake, but something like that as well.
 
I have a 2020 chevy trail boss with 40k miles on it. I bought it with 23k so second owner. Anywho I noticed a huge drop in fuel mileage 2 oil changes ago. Was averaging 17 to 18 mpg but now I'm at 10 to 11 mpg. I've switched fuel, where I have purchased fuel, I'm also driving about the same speeds everyday. I haven't done pen and paper yet I was just going off by my monitor/dash screen. Even if it's not right I can tell my fuel mileage has gone down. I do usually put 87 in it but if I was getting the good mileage with it why all of the sudden drop? No codes nothing seems wrong it drives great and throttle response is solid. Any insight would be greatly appreciated!
What engine do you have? I know the 5.3 and the 6.2 call for 91 or better octane. You should see some improvements with the higher octane, enough to offset the cost. But that still doesn't explain the big drop. Does it seem like you are filling up more often, aside from what the screen mileage says? You might go ahead and do your pen and paper calculations just to double check. Does power seem like it has gone down? You might double check your air filter and make sure all vacuum lines are tight.
 
Any ethanol in the fuel you are using? It'll lessen your range over 100% gasoline... (E85 = 25% less MPG)
Other changes? Bigger tires? Lift?
If not, maybe hook up a scanner and check the long term fuel trim for too rich, but not significant enough to set a code. If you have a vacuum leak or other situation causing the computer to see lean, it will add fuel, within the parameters of its programming, to compensate and MPG will suffer.
Agreed on the ethanol. And it is a messier combustion too. Ethanol-free and top tier is the way to go for sure.
 
All these are pretty solid thanks everyone! As for the truck it's a 5.3 so the next time I go fuel up I'll do some pen and paper and use 91 not 87. I have noticed im at the fuel station more. The truck is still all stock I haven't changed anything to it yet. Everything seems fine and runs great. The only thing I have noticed maybe and that's maybe is that the active fuel management has been kicking in more often and my golly I absolutely can't stand that. Makes the truck sound like shit. I have a code reader but doesn't go into all the parameters for fuel. I do know someone who has one. I have been looking at getting a chip to delete the active fuel management. Is there any suggestions on what to get?
 
Mine is the 5.3 and it gets horrible mileage. Right now its average is showing 12.6 for the last 50 miles. I shut off DFM and auto-stop, and increased the throttle response with the programmer and it was getting 11mpg! When I got the programmer, I also added a S&B Cold Air Intake and RC Exhaust, which I thought would actually help fuel economy, but apparently not. Even with stock wheels and tires, which are now 33x12.5 MT, and everything else stock, I think it was running 13-14mpg. I might try better fuel...or maybe buy a Rivian...lol!
 
Agreed on the ethanol. And it is a messier combustion too. Ethanol-free and top tier is the way to go for sure.
I get 2-3 more mpg with non-ethanol. I've gotten as much as 27mpg on a 35 mile trip which has hills and according to the elevation figures between the two towns it's downhill about 600 ft. Round trip for 5 days averaged 25 mpg. Now that's not driving normally, that's driving conservatively for better mileage.
 

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