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Old February 12th, 2010, 01:26 PM   #1
samuraijunkie
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Default 2000 chevy malibu bad MPG ?????

My car is getting really bad gas mileage and I have no idea why mabe i missed something. Its getting about 17-21 mpg. Its a 2000 with the 3.1L V6 98,000 miles, runs great good power not getting the same mileage i used to around 27-29mpg

New parts: Plugs, wires, trans fluid and filter, Air filter, Oil change. Even ran some sea foam through the gas and only it only went up to 22mpg on that tank and then droped back down

Checked tire press its good. No brakes hanging up tires spin free when lifted off the ground I'm at a loss
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Old February 12th, 2010, 01:31 PM   #2
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Hows the coolant? Those motors are notorious, and I mean NOTORIOUS for LIM gasket failure.

LIM = lower intake manifold

When you run seafoam it does tend to increase your mileage slightly....FYI

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Old February 12th, 2010, 01:31 PM   #3
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Are you measuring the difference between what you were getting in the summer and what you're getting now in the middle of winter?

It's pretty common for your gas mileage to drop that much in the winter.

Winter fuels are concocted with a shorter hydrocarbon chain. This is because evaporative emissions aren't an issue, but trying to get the fuel to ignite in cold weather is. The shorter the chain, the easier it will be ignited. Summer fuel is the opposite. Longer hydrocarbon chains mean the fuel has a little more energy to it.

You're also usually idling the car more, and it is taking much longer for the car to warm up and reach closed loop, and until then the car is running rich when in open loop.

I usually get around 27 MPG in the summer, and drop down to about 22-23 in the winter.

Other than that, only thing I could recommend would be doing a compression test.
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Old February 12th, 2010, 01:33 PM   #4
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Did you change the fuel filter?
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Old February 12th, 2010, 01:38 PM   #5
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Quote:
Originally Posted by greygoose View Post
Hows the coolant? Those motors are notorious, and I mean NOTORIOUS for LIM gasket failure.

LIM = lower intake manifold

When you run seafoam it does tend to increase your mileage slightly....FYI
The coolant is good so i don't think its an intake manifold no spots on the snow and no missing coolant. The seafoam does help but not much and only on the tank with the seafoam in it.

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Did you change the fuel filter?

Fuel filter is stock
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Old February 12th, 2010, 01:40 PM   #6
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Quote:
Originally Posted by samuraijunkie View Post
The coolant is good so i don't think its an intake manifold no spots on the snow and no missing coolant. The seafoam does help but not much and only on the tank with the seafoam in it.




Fuel filter is stock

Well is should be changed about every 30k
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Old February 12th, 2010, 01:43 PM   #7
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I'll pick one up today its a little past 30,000 close to 60,000 past should i get two just for good measure?
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Old February 12th, 2010, 01:47 PM   #8
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When did you measure the 27-29 MPG compared to what you're getting now?
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Old February 12th, 2010, 01:57 PM   #9
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I've gotten that before (not this year) it was steady when i bought it about 3 years ago even in the winter up until this winter late fall when it went in the shitter
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Old February 12th, 2010, 02:04 PM   #10
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Stop by a Vatozone and borrow their code reader - see if you have any trans issues that wouldn't necessarily light the MIL. (such as TC not entering lockup)

If anything, fuel economy should improve with miles.
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Old February 12th, 2010, 02:06 PM   #11
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Well 3 years ago not all gas had 10% ethanol in it, now they all do. I would assume that would contribute to a mileage drop as well.
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Old February 12th, 2010, 02:09 PM   #12
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Quote:
Originally Posted by scooter View Post
stop by a vatozone and borrow their code reader - see if you have any trans issues that wouldn't necessarily light the mil. (such as tc not entering lockup)

if anything, fuel economy should improve with miles.
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Old February 12th, 2010, 02:48 PM   #13
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Quote:
Originally Posted by IFS SUCKS View Post
p1811
What does a trans code have to do with it unless the TCC isn't engaging?

Put a new fuel filter on it. Do a compression test and a fuel pressure test.

See if the compression and fuel pressure are up to spec. Pretty much most of what you replaced will fix poor fuel mileage, and usually poor fuel mileage is associated with some other drivability concern.
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Old February 12th, 2010, 03:08 PM   #14
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I have also noticed my truck is down on MPG since the cold weather is here.

It is normal for this to happen. Cold air is more dense and needs more fuel.
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Old February 12th, 2010, 09:30 PM   #15
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Quote:
Originally Posted by GreaseMonkey View Post
Are you measuring the difference between what you were getting in the summer and what you're getting now in the middle of winter?

It's pretty common for your gas mileage to drop that much in the winter.

Winter fuels are concocted with a shorter hydrocarbon chain. This is because evaporative emissions aren't an issue, but trying to get the fuel to ignite in cold weather is. The shorter the chain, the easier it will be ignited. Summer fuel is the opposite. Longer hydrocarbon chains mean the fuel has a little more energy to it.

You're also usually idling the car more, and it is taking much longer for the car to warm up and reach closed loop, and until then the car is running rich when in open loop.

I usually get around 27 MPG in the summer, and drop down to about 22-23 in the winter.

Other than that, only thing I could recommend would be doing a compression test.
Plus your tires are colder increasing rolling resistance and cold air is denser there for it takes more horse power to push a car through 0 degree air vs 70 degree air.

Many many factors cause you to get worse gas mileage in the winter...wifes truck went from 20mpg to 13mpg!!!
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