Gas mileage 12MPG on a 2000 Dodge Caravan with a V6. What could be wrong?

Question

The van runs very well, recent tune up, oil change every 3000 miles. Has around 80,000 miles. No other problems. I do live in a hilly area, but it's only uphill 1/2 the time!! ;)

OK- Thermostat looks good. The mechanic said the O2 sensor looked good on the scope, but was a little slow. We changed it. He said it had the wrong plugs (single platinum, should be double platinum) He changed all the plugs. The catalytic converter checks out good. The van runs good. Still 12 MPG.

More history- About a year ago I bought a house on a hill. Within the first week this van blew the transmission. The transmission was rebuilt. My recollection is when I was a “flatlander” I used to get 16-18 MPG with a similar driving pattern minus the hills. I figured the hills could hurt the mileage a little, but the downhill part would also help somewhat.

Half of my driving is on an engine that is not hot. I drive city driving only 6 miles downhill to work (1 stop to drop off kids at school) about 25 minutes one way. Then 6 miles uphill (again stop to pick up kids) another 25 minutes. Maybe with this type of driving, I should only expect 12MPG?

Answer 1

O2 sensor a likely possibility - can cause significan loss of mileage depending on condition and driving habits. Clogged converter is also a possibility, but often comes with other problems. Can also be a combination of O2 sensor and Cat. Converter. A clogged converter will sometimes cause and already worn O2 sensor to really act up. I'm assuming the van used to get better mileage. Check your filters of course and maybe buy gas at a few different places - likely won't help, but worth a shot.

Since you say your previous mileage was 16-18 (lower than I thought) The yes, the hills can matter.

A caravan, even one with a V6, is carrying a lot more weight that a car with a similar engine. It boils down to engine load. My truck with a 4.7 V8 gets around 17.5 MGP. When I go into hilly areas I've calculated it to be as low as 13 MPG. When towing a 1100lb trailer (empty) I get 12-13 MPG. Most likely you are applying more throttle at all times than you need, and not taking advantage of the torq curve. For instance, a stock vehicle will generally accelerate as fast under 3/4 throttle as it will full throttle from a stop, and burn less gas. THe extra load produced at full throttle is wasted. The next time you find yourself on flat land, play with your accelerator and find the point at which you are applying only minimal throttle. If you press the accelerator down very slightly you'll find that your speed hasn't increased, nor has your engine speed in RPM's. It's that range in which more acceleration doesn't produce more speed that your engine experiences uneccessary load. Play with that and adapt it to the hills.

Also check your trans fluid, have it changed if neccessary to make sure the torq converter is working efficiently. Little stuff adds up fast when it comes to MPG

Answer 2

This Site Might Help You.

RE:
Gas mileage 12MPG on a 2000 Dodge Caravan with a V6. What could be wrong?
The van runs very well, recent tune up, oil change every 3000 miles. Has around 80,000 miles. No other problems. I do live in a hilly area, but it's only uphill 1/2 the time!! ;)

Answer 3

Dodge Caravan Mileage

Answer 4

2000 Dodge Caravan Mpg

Answer 5

A bad thermostat will cause the van to run richer then it should. Does the Temp gauge read normal ( striaght up in the middle?) Also, A slow switching or lazy O2 sensor will cause poor mileage. Another possibility is a bad fuel Pressure Regulator

Answer 6

Did it start after the tune up ?
cheap parts arent always the cheapest in the long run.
Lazy O2,dirty air filter,wrong spark plugs,may need new wires,
Take to a good shop and pay for a Daig, $80 - $100 might save you some money on gas

Answer 7

O2 sensors are probably bad,
During the tune up someone may have disconnected a vacuum line too.
Have a mechanic hook it up to a scanner and get the readings from the o2 sensors to make sure they are doing their job before replacing them though.
Try a good fuel injection cleaner and change that fuel filter!

Answer 8

A clogged cat will kill the mileage. Thermostats and sensors wouldn't hurt it anywhere near that much. A muffler shop can tell you if it's an exhaust problem real quick.

Answer 9

gas leak maybe??? that thing should be getting over 20 for sure. get an exhaust pressure test done, usually only 25 bucks or so and anything over 1psi is bad and a plugged exhaust will cause MPG problems

Answer 10

I was trying to reply to a message you sent me but it wouldnt send. I have no idea about your van but I wanted to say,Thanks. I hope that maybe it helps someone who is also afraid to die. Maybe they won't feel alone.