Unusually Poor Gas Mileage

[SonicBoomhauer]

Well, another week has gone by, and I have tried changing things up some, including getting out of first gear quickly, and doing exactly the speed limit. I've also used premium for my last three fill ups.

Still getting the EXACT same mileage, no matter what I do. I have yet to crack 30 mpg, and have done 80% highway driving.

I'm extremely aggravated. I bought this car because I wanted something that got great gas mileage. My Sonic has been getting exactly the same mileage that my 2005 Outback 2.5i gets on the highway.

Something is clearly wrong with the car. There's no reason in hell I should only be getting 27-29 mpg when cruising at 75 mph at 2100 rpm...


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[SonicBoomhauer]

Side note, the car is an LT 1.4 turbo with the six speed manual. Not an RS. If this was an RS I would be a lot less annoyed, but hell, I see most people with RS's averaging 33, and most LT owners getting 35-39 combined, so why on Gods green earth am I getting such piss poor mileage, especially when I've got my tires aired up properly, I'm using premium fuel and I'm driving it fairly conservatively.

I'm going to Portland/Seattle for a week, but when I get back, I am taking it into a Chevy dealer and having them run diagnostics.


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[Cavell219]

Well, another week has gone by, and I have tried changing things up some, including getting out of first gear quickly, and doing exactly the speed limit. I've also used premium for my last three fill ups.

Still getting the EXACT same mileage, no matter what I do. I have yet to crack 30 mpg, and have done 80% highway driving.

I'm extremely aggravated. I bought this car because I wanted something that got great gas mileage. My Sonic has been getting exactly the same mileage that my 2005 Outback 2.5i gets on the highway.

Something is clearly wrong with the car. There's no reason in hell I should only be getting 27-29 mpg when cruising at 75 mph at 2100 rpm...


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Having the same problem as you, 1.4T terrible gas mileage. I had to have the water pump replaced last week and have an engine noise at 1800-2400 RPM that happens in all gears that the dealer can not figure out. I think there is a problem with my turbo.

//Begin Rant about MPG
Just drove 750 miles highway and averaged 30.8 MPG, temperature was 48-60 there and back. Speed was with cruise Control. November did the same drive with close to same temperature, was a little colder and got 40MPG... Big difference.

Currently my last 3 fill ups excluding the trip were 25.3, 25.7, and 23. 70% HIghway. It is getting very upsetting. My G6 got me the same gas mileage, and I traded for better gas mileage. I have been to the dealer about my gas mileage now twice and they tell me the sonic averages 25 and there is nothing wrong... Then why does the EPA say 33 for the turbo...

/End Rant

 

[SonicBoomhauer]

So I'm not the only one having this issue. Luckily I have been keeping track of my mileage on Fuelly, I'm going to shove the fuel records in front of the service manager and say 'explain this'.


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[Cavell219]

So I'm not the only one having this issue. Luckily I have been keeping track of my mileage on Fuelly, I'm going to shove the fuel records in front of the service manager and say 'explain this'.


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I have my gas mileage taken with an app called aCar on Android from when I had 1200 miles on my car. It has every time I have stopped at a gas station. It didn't help. I hope you have better luck than me.

 

[SonicBoomhauer]

It's pretty simple - if the dealer can't resolve my mileage issue in the next couple thousand miles, I'll have no choice but to trade it in for another hatchback that will actually get the advertised mileage. Which would make me very sad, because I genuinely love the snot out of my Sonic, but I absolutely NEED a vehicle that gets 35-40 mpg consistently. :sadbanana:

 

[barrstev]

I shift from 2-4-6th gear. I don't even bother with first. I get horrible gas mileage over 60mph in my RS. Cold weather kills your mileage because air is more dense which results in much greater aerodynamic drag. EPA mileage tests reach a max speed of 60mph. You may also be pressing harder on the gas pedal than you need to. If you want to get better mileage, find the sweet spot on the gas pedal where you are pressing so lightly that that you just about lose speed. At 55-60mph with my RS and drafting a semi I've been able to get 40mpg. Driving at 75mph I get closer to 27mpg (actual). Check out the speed penalty calculator to see why your mileage sucks. Your subaru got better mileage because it wasn't a boxy hatchback...

Gas Mileage Tips - Driving More Efficiently

 

[Stew]

EPA mileage tests reach a max speed of 60mph.

Actually, since 2008 the max speed is 80 mph on the high speed test.

https://www.fueleconomy.gov/feg/fe_test_schedules.shtml

 

[mitdr774]

Look at the average speed though. Epa test cycles are unrealistic. That being said my 1.8 is at an average of just over 35mpg for the last 40k miles or so.

People that get bad economy usually need to adjust driving style and habits.

 

[XilliK]

I've got a 2014 RS and have at best gotten around 29 mpg have been only using premium, grades here are 86 88 and 90 I believe so gonna try plus and see if there's improvement... my drives are mostly highway going to work and I may need to fill up about every 3 days...

 

[XilliK]

UPDATE just put a couple gallons of plus in and the MPG difference was immediately noticed, from 28 to 40 wow all those like 5 fill ups almost just wasted...

 

[Dirkdaddy]

Good...keep up on it! You may have had a sensor not showing temperature properly (engine temp might do it) and it could have run rich on the fuel mixture...some things don't throw a code. But someone with a tool could check fuel trims and other diagnostics but unfortunately people who really understand these things are the harder to find. Most mechanics are parts swappers.

 

[RMinNJ]

I've noticed my MPG has gone down with the cold weather we're finally having in NJ.
Like 38MPG now down to 33-34 on the display.

 

[Hdmanny]

UPDATE just put a couple gallons of plus in and the MPG difference was immediately noticed, from 28 to 40 wow all those like 5 fill ups almost just wasted...

There had to be something wrong, there is no way that using plus would increase you gas mileage almost 50%. I agree that it must have been running rich and it was correct about the time you used the plus gas. I average about 35 mpg per week so if I used plus I should get over 50 mpg.

 

[XilliK]

There had to be something wrong, there is no way that using plus would increase you gas mileage almost 50%. I agree that it must have been running rich and it was correct about the time you used the plus gas. I average about 35 mpg per week so if I used plus I should get over 50 mpg.

Yeah well from the pump to home it climbed quickly to 40, then as I leave again just now it switched down to 32 not sure how that happened and city it's staying at about a steady 31 32

 

[NewZJ]

I'm at 31-32 average. With a few mods. And I drive it like I stole it

 

[redhot1.4]

I run nothing but 93 shell Vpower. Driving like I'm 65 I got 36 38mpg. But my normal driving 32 33mpg.

 

[XilliK]

Yeah I only ever put shell or chevron gas in it... unleaded is 86 so don't think that would be suitable. About 2-3 better MPG than putting premium figured it would be better for the turbo... I got a 14 RS should I be getting closer to 40 MPG?

 

[perrymk]

I got a 14 RS should I be getting closer to 40 MPG?

I believe the RS version is rated for 34mpg highway. The LT version with the 1.4T and 6 speed manual is rated for 40mpg highway.

I have a 2014 Sonic LT 1.4T 6 speed manual and typcially get 37-38mpg calculated, dashboard display is 39 mpg. Most of my driving is what I call stop-and-go highway and I drive for gas mileage as much as possible. Also, I only use non-ethanol gas.

 

[Italianjoe1]

I get 27 avg in my turbo 6at hatch but it's got 17" wheels with beefier tires, and a tune with more boost/fuel. I strongly prefer being able to drive the car aggressively and get out of my own way to saving a little gas money, traffic in south FL is brutal and if you try to drive like you want to hit 40mpg you are likely to get run over by a truck.