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Discussion Starter · #1 ·
My daughters 2001 V6 (not 4motion) averaged ~19 MPG when she got it 3 years ago with 63,000 miles. Now, at 83,000 miles, it's averaging ~16 MPG. This is mostly town driving.

I don't know what and when things were done to the car by the previous owner when we got it with 63,000 miles.

I put a new air filter in it a while back and just checked it. It had very minimal dust in it when I blew it out with compressed air.

The car seems to run good. Starts great.

What are some of the most likely culprits with this engine that could be responsible for the drop in mileage?

Thanks.
 

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A scan with VCDS to check fuel trims would be the most helpful. Has the timing belt been changed? How about the plugs? Perhaps she's gotten used to the car and uses the gas pedal more? Do they add ethanol to the fuel up there or run winter gas?
 
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Discussion Starter · #3 ·
A scan with VCDS to check fuel trims would be the most helpful. Has the timing belt been changed? How about the plugs? Perhaps she's gotten used to the car and uses the gas pedal more? Do they add ethanol to the fuel up there or run winter gas?
Thanks for you reply.

Yes, I do know that the timing belt has been changed...shortly before we bought the car. I don't know about the plugs....and I'm not sure about her driving habits. I considered that but....my guess is that her habits aren't much different. She's a timid and cautious driver. As far as ethanol....yes. There are not many pumps here with ethanol free gas. She uses the 91 octane with ethanol.
 

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PZ has a great suggestion to do the scan.

Other things things I would at least check out:
1) Make sure the CEL is not on.
2) Make sure the PCV system is all in tact.
3) Check to make sure all tires are at correct pressure.
4) Make sure non of the brakes are dragging.

The low mileage on this car is impressive, however just the age of the car could compromise some of the systems like the PCV system.
 
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Discussion Starter · #5 ·
PZ has a great suggestion to do the scan.

Other things things I would at least check out:
1) Make sure the CEL is not on.
2) Make sure the PCV system is all in tact.
3) Check to make sure all tires are at correct pressure.
4) Make sure non of the brakes are dragging.

The low mileage on this car is impressive, however just the age of the car could compromise some of the systems like the PCV system.
Thanks. I don't have a scanner but a friend does. If his doesn't fit, I'll ask my mechanic to do it while the CV joints are being replaced.

Excuse my ignorance (I'm just a backyard mechanic w/ knowledge of older technology ie, 60s, 70s era) but what is the CEL?
 

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Your air cleaner's condition won't affect gas mileage in a MAF sensor car, like the old carburetor cars, so that's not it. One thing that can is the coolant temperature sensor, which tend to go bad at some point, and yours could be 20 years old. If the coolant temperature signal being read by the engine control unit is incorrect (too cold), then the mixture will be too rich and lower the fuel mileage. These are inexpensive and not a terrible chore to change; AndreasPassat has covered this before. And as he said; air up the tires- to the max shown on the door jamb label.
 

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One thing that can is the coolant temperature sensor, which tend to go bad at some point, and yours could be 20 years old. If the coolant temperature signal being read by the engine control unit is incorrect (too cold), then the mixture will be too rich and lower the fuel mileage. These are inexpensive and not a terrible chore to change.
Good call on the coolant temp sensors. Completely forgot about that.
 
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