Gas mileage


Old 06-28-12, 08:13 AM
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Join Date: Jul 2003
Location: USA
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Gas mileage

I own a 2000 Town & Country van with a 3.8 liter v6 engine. It has 160000 miles on it and the spark plugs have 35000 miles. Recently the gas mileage has dropped from 19 to 16 city and 24 to 21 highway. I think it may be an oxygen sensor, but the check engine light has never come on.

Where is the most likely oxygen sensor located? Seems it might be worth a try. Any suggestions?
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Old 06-28-12, 08:35 AM
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Even without lights, there may be a code in the computer, I would start by having that checked.
Old 06-28-12, 08:56 AM
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Could have as many as 4 O2 sensors, not sure on a T&C. They're in the exhaust between the engine and cat converter and/or after the cat. Usually pretty easy to spot, but can be difficult to access for replacement.

Like Mitch, I would investigate other possibles before condemning the O2 sensors. How old are the plug wires, for instance, and has the air filter been replaced lately? Dirty MAF sensor another possible. Tire pressures, dragging brake(s), lots of things on the troubleshooting list.
Old 06-28-12, 09:20 AM
Join Date: Jan 2012
Location: Canada
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I don't know if I would go swapping sensors for that small of a drop.
There are so many little things that on their own, or in conjunction with other things, could drop your millage by that much or more.

First thing to check; regular maintenance
- air filter
- tire pressure (use tire specs, not inner driver door specs)
- transmission fluid level (flush and fill if it hasn't been done over within the last 50k miles)
- check and change all other fluids if needed (again, your high millage, should be done anyway)
- Carbon clean out. Mopar has an amazing system (fuel attitive and fog) that works wonders.

I would suggest also remove unnessessary stuff from your vehicle. I know our van accumulates stuff pretty quickly and as a result, the van is moving more weight then nessessary.

Other conditions that will affect your millage are;
- fuel quality (winter gas gets worse millage then summer)
- temperature
- road conditions
- type of roads (hilly vs flat)
- road conjestion
- engine temp (better millage over longer run times vs. short trips)
- Frequency of engine starts per tank (more engine start ups results in worse millage)

Also, where you using your A/C both when you where getting the first average, and when getting your second? A/C puts a load on your vehicle and in city driving, will really impact the millage. Our 07 Grand Caravan (3.3l) sees a 5-10% engine load increase with the A/C on while city driving. My car (08 Caliber SRT4) sees 2-5% increase in load.

Because of my long commutes to work (100miles of hwy, round trip), I have really started watching my driving and both our vehicle's performance. I now have a device called a ScanGaugeII which gives me a reading of most of my sensors and if the need comes, check and clear engine codes (pending codes or Check engine light codes).
I have used this to adjust my driving habbits which has helped a bit. On the car, I have dropped my millage down from ~8.6L per 100km to ~7.9L per 100km on average. For a small crossover with more then 300hp at the wheels, this makes a huge difference.

My suggestion would be to start with the basic maintenance stuff listed at the top and go from there.
Old 06-28-12, 09:41 AM
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Mike those must be Canadian The US version only listed 285 hp.

Looks like yer getting about 29 mpg though (I think)...thats pretty darn good.
Old 06-28-12, 11:06 AM
Join Date: Jan 2012
Location: Canada
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Ya, it was about 285hp, 265ftlb torque when it was stock. Not so stock anymore.

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