Is My Average MPG Guage Off or Something Else? - Chevy Cobalt Forum / Cobalt Reviews / Cobalt SS / Cobalt Parts
All about MPG All about maximizing your Miles Per Gallon (MPG)

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post #1 of 12 (permalink) Old 03-24-2012, 09:47 PM Thread Starter
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Is My Average MPG Guage Off or Something Else?

most of you know that i have been trying to improve my MPG with different methods the last couple of months.

i was averaging around 36 mpg (my calculations) along with my average MPG on my car. ( there would maybe be only a .5 MPG differance) pretty regularly but here lately its been a mile or two lower. i know, its not that big of a deal. well what i am concerned about is, i drive a strait shot highway road every day to work and hold my car at 55 98% of the time and coast my car as much as possible and my average MPG meter slowly goes up and it usually peeks at about 37 mpg and almost never drops more than maybe .3 on a daily bases. it will stay roughly around 37 on my average MPG untill im out of gas then i go and fill my car up with gas and do the math and with my calculations it says i am only getting between 34-35. i stop filling the car on the first pump shut off, i do not over fill it.

is there a reason my average MPG and my calculations are so far off? again, its only off about 2.5 MPG but why does my car say i should be getting more? i am going to try to change my air filter and see if that helps.

in a side note, with going 55 and coasting my car every day shouldnt my MPG be over 35 anyway? if i run 60 and dont coast my car i can usually run around the low 34's. it dont really add up there for me, you would think running slower and coasting would make the MPG a decent amount more. if im only going to gain roughly 1 more mpg with going 55 and coasting then IMO i dont think its really worth it. i literally take my time getting up to speed too, rather than just speeding off.

any opinions are welcome.

BTW, i know i might be taking this MPG too far but im hooked lol


Last edited by bean2080; 03-24-2012 at 09:50 PM.
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post #2 of 12 (permalink) Old 03-25-2012, 03:56 AM
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Mine is off also in favor of GM. It reads 8.2 liters per 100 kms but I calculate 8.9. So yours appears to be as inaccurate as mine. But once you know it serves as a reference point.

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post #3 of 12 (permalink) Old 03-25-2012, 07:36 AM
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Mine is either under by 1 mpg or over by 0.5 mpg.
Maybe use the same pump every time.

If your an auto coasting won't help you much and you actualy don't want to accelerate that slowly.
The goal is to open the throttle as much as you can without the car downshifting and then tricking the car to shift at low rpms (2,500 - 3,000).

In my wifes auto Malibu I have to steadily increase pressure on the accelerator and then let off a bit between 2,200 - 3,000 rpms to cause the car to shift up. Then I put as much pressure as I can without causing the car to downshift again and as revs raise I can put a little more pressure on the throttle.

Think of it this way, if the throttle is only open a little it's like the engine is trying to breath in air through a coffee stirrer instead of at full open throttle a paper towel roll.

But you need to keep rpms down or the engine richens the air fuel ratio.

Only mod I've done to her car is pumping tires up to 38 psi and they are some junk discount tires, not even LRR (low rolling resistant).

I can get 38+ mpg doing 60+ driving between Raleigh, NC and Baltimore, MD and her car is a 3.5L V6.

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post #4 of 12 (permalink) Old 03-25-2012, 07:39 AM Thread Starter
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thanks for the info guys, ill give that stuff a shot and see where i end up. its all trial and error lol

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post #5 of 12 (permalink) Old 06-07-2012, 11:14 PM
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ive noticed mine going up when i give it more gas at the beginning (first and second gears)
and then taking my foot off the gas a little and getting up to 60 about half throttle
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post #6 of 12 (permalink) Old 06-07-2012, 11:21 PM
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post #7 of 12 (permalink) Old 06-08-2012, 02:00 AM
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I use cruise control on straight shots and i get around 45.... @ 53 MPH
& use your foot going up hill, and make it shift at 2,500 - 3,000 RPM like he said.


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post #8 of 12 (permalink) Old 06-08-2012, 05:40 PM
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JacksonWilder3: Does your signature really say 1% tint all around? Damn, that's DARK! I like it!



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post #9 of 12 (permalink) Old 06-09-2012, 12:10 AM
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Yep Had to special order it off eBay
What % is yours?
I love the silver.


2010 Cobalt 2LT Sports Package
2.5% tint all the way round.
SUPRRAAACHARRRGGEDDD
2.9 pulley, 60# Injectors, Injen 2.5" intake
55 Watt 6000K Hi/Lo HID's
35 Watt 5000K Fogs
Black SS 17" Wheels
Debadged
Spyder 3" Carbon Fiber Antenna
YAKIMA ROOF RACK WITH 40" LIGHTBAR
2.5' ZZP DP
Full set of Black Recaros
Eibach sportlines for teh low.
Front and rear SS lips
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post #10 of 12 (permalink) Old 06-12-2012, 06:56 PM
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Very nice! I have 35% on the front sides and 20% on the rest. I used to run 20% or darker on my cars but got tired of of being stopped and "knowing someone" for an inspection sticker



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