[Jdaugh01]

Hello, all!

I have a 2007 Odyssey EX-L w/RES. For the first three years, it got around 400 miles per tank of gas (both city and highway driving). For the past six months or so, it doesn't get more than 260 miles per tank of gas. Taken it to the dealer three times ... no error codes, dealer is clueless. We've tried EVERYTHING, checked everything, with no solution. I love my van, but I'm seriously considering selling it. Any ideas? Thanks!

 

[mindoro]

Sorry to hear about the drastic drop in mileage. Ques: Have you tried an independent shop? Perhaps something IS wrong, but the dealer does not want any part of it....

Also, what is the current mileage of the van?

 

[sontakke]

Frozen calipers are often overlooked. That would kill the mileage quickly.

 

[noanswer]

Have you noticed any difference in driving dynamics?

Have you noticed any difference in engine or transmission noise?

Are you sure you're completely filling it up? Sometimes the gas tank vent tube gets clogged and cannot vent properly which causes some gas pumps to shut off early, though you may think you're filling it up (especially with gas prices today).

You could also have a bad fuel level sending unit which goes to empty before it's time, which would leave you filling up on a half or quarter tank full.

Tire pressure good? Oil changed regularly?

Any change what so ever (other than reduced range) such as less power/sluggish response, etc.?

Are you suddenly delivering masonry building supplies for a living (or regularly carry anything else significantly heavy)?

I know some of these questions are obvious, but you never know what some people expect.

 

[Jdaugh01]

Sorry to hear about the drastic drop in mileage. Ques: Have you tried an independent shop? Perhaps something IS wrong, but the dealer does not want any part of it....

Also, what is the current mileage of the van?

Current mileage is 60k. Talked to a couple of mechanics who have said they wouldn't do anything different than the Honda dealership. I have a couple of mechanic friends who are baffled that there are no error codes.

 

[Jdaugh01]

No real difference in driving dynamics. Maybe a very slight surge at times when driving on the highway. No weird noises and yes, we have made sure it is completely filled up. Good tire pressure, oil changed regularly. No bricks in the back Dealer assures me if there was a problem it would throw a code. So since there's no code, they say they can't do a darn thing! I have noticed a small group of Ody owners who get horrible MPG. Maybe I just got a lemon. I hate to sell the van to someone else though knowing this info.

 

[UmmGooD]

No real difference in driving dynamics. Maybe a very slight surge at times when driving on the highway. No weird noises and yes, we have made sure it is completely filled up. Good tire pressure, oil changed regularly. No bricks in the back Dealer assures me if there was a problem it would throw a code. So since there's no code, they say they can't do a darn thing! I have noticed a small group of Ody owners who get horrible MPG. Maybe I just got a lemon. I hate to sell the van to someone else though knowing this info.

If you fuel up at the same station every time did they add Ethanol mix to your fuel recently? I know here in Austin I used to be able to get 100% gas but just recently it seems like more and more pumps now have the Ethanol blend gas and it really effects the mileage on my cars.

 

[Jdaugh01]

If you fuel up at the same station every time did they add Ethanol mix to your fuel recently? I know here in Austin I used to be able to get 100% gas but just recently it seems like more and more pumps now have the Ethanol blend gas and it really effects the mileage on my cars.

Yep, we've tried different gas stations, as well. Dealer suggested using premium for a couple of times, which we did, and we gained about 30 extra miles.

 

[davedrivesody]

How is the air filter?

Also, have your mechanic check the temperature of the exhaust manifold. A partially blocked cat converter will cause it to overheat (and reduce engine performance).

 

[Dirkdaddy]

Your engine may be staying in "cold" mode (open loop) longer than it should which would lead to richer fuel mix and less MPG and discolor most of the plugs, or an injector that's spewing more fuel than needed - that would discolor 1 plug, and its possible either one would not throw a code. Faulty sensor could give less spark advance which lowers power and uses more fuel...etc. You need better mechanics and have them spend time doing diagnostics (and you have be willing to pay for this) instead of swapping parts or throwing up hands in the air. The brake issue could also cause problems as noted, or more obscure things like dragging accessory drives, clogged air filter, etc. Good luck.

 

[redmondjp]

A lot of good suggestions above. I also suspect the winterized fuel could be your culprit based upon your timeline (past 6 months). That should be phasing out soon if not already depending upon where you live. So I'd ask around at your fuel suppliers and run a month after you know they have switched back over to summer fuel and then see if you still have the issue.

I'm assuming that you've already gotten the vehicle up on a lift or jacks and checked that each wheel turns easily, and that your brake calipers are properly releasing (spin wheel by hand, have helper apply and then release brake pedal, wheel should freely turn again immediately)? Obviously the front wheels are a bit more difficult to turn due to the friction in the drivetrain components.

I would also second the recommendation to find a good, independent shop with a first-rate driveability/diagnosis tech (yes, they are few and far between). Somebody who has a high-dollar scantool and knows how to use it. They can ride with you and check parameters while you are driving such as injector duty cycle and O2 sensor switching which may lead to the culprit. I think that some scantools can even monitor fuel useage IIRC.

I feel your frustration; I recommend looking at this as an opportunity to put on your detective hat and to outsmart the car (it really ticks me off when the car wins!).

 

[OddDrive]

Your engine may be staying in "cold" mode (open loop) longer than it should which would lead to richer fuel mix and less MPG and discolor most of the plugs, or an injector that's spewing more fuel than needed - that would discolor 1 plug, and its possible either one would not throw a code. Faulty sensor could give less spark advance which lowers power and uses more fuel...etc. You need better mechanics and have them spend time doing diagnostics (and you have be willing to pay for this) instead of swapping parts or throwing up hands in the air. The brake issue could also cause problems as noted, or more obscure things like dragging accessory drives, clogged air filter, etc. Good luck.

Similar idea - could the thermostat be broken? Is the temp gauge going up to almost 1/2 way? When you turn the heat on, is it as hot as it should be?