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Michael Gabbay
01-13-2006, 10:33 AM
Over the past several fill ups, I've noticed that my gas mileage is off by a couple of mpg in my Honda Pilot. I've been driving the same commute to work and using the same type of gas. The only thing that has changed is I took it into the dealer a few weeks ago to get the 13K mile service (oil change, tire rotation, filters etc.).

I normally average 18 mpg, now I'm getting around 16mpg. For all of the grease monkeys, any ideas for such a dramatic decrease in mpg?

Mike

John Miliunas
01-13-2006, 10:38 AM
Mike, I'm far from a "certified" grease monkey but, I can't help but wonder if while they were in there swapping stuff out, if a vacuum hose didn't inadvertenly get disconnected? :confused: :cool:

Mark Cothren
01-13-2006, 10:52 AM
I'd double check air pressure in tires, visually inspect for any loose vacuum lines as John has suggested, and also inspect your air filter/cleaner to make sure they changed it and it isn't clogged up.

Are you noticing any change in performance (loss of power, etc)?

I took a vehicle in to a dealer for some work and had them do a tune up while they had it in there. I was billed for a full tune up (including plugs and wires) and less than a week later when I had a miss in the motor I realized that I still had the same plug wires - not the new ones I paid for...:mad:

John Miliunas
01-13-2006, 11:03 AM
I took a vehicle in to a dealer for some work and had them do a tune up while they had it in there. I was billed for a full tune up (including plugs and wires) and less than a week later when I had a miss in the motor I realized that I still had the same plug wires - not the new ones I paid for...:mad:

Eeeeeek! :eek: And on today's motors, them thar wires are some of the most expensive components on the tune-up!!!:mad: Hope you got it resolved!!!!:) :cool:

Dan Larson
01-13-2006, 11:22 AM
Have you been having colder than usual weather lately? Outdoor temp can influence mpg significantly. Granted you have a more moderate climate than we have here in WI, but my average mpg drops by as much as 15% during the dead of winter.

Dan

Bob Johnson2
01-13-2006, 11:22 AM
I live a bit farther north, but I get a couple mpg less in the winter, don't really know why. I know the gas formula is different this time of year, but that's just a guess.

Dan Larson
01-13-2006, 11:26 AM
I live a bit farther north, but I get a couple mpg less in the winter, don't really know why. I know the gas formula is different this time of year, but that's just a guess.
I think it has to do with engines needing to run on a precise fuel:air ratio. Cold air is more dense, so more fuel is needed to maintain the correct ratio. Side benefit of this is that the engine makes more power on a cold day.:D

John Miliunas
01-13-2006, 11:28 AM
Have you been having colder than usual weather lately? Outdoor temp can influence mpg significantly. Granted you have a more moderate climate than we have here in WI, but my average mpg drops by as much as 15% during the dead of winter.

Dan

Ditto! Don't that just suck??? :mad: Doesn't really seem to improve significantly until the temps start to top over 30, either! Oh well...At least it's not as bad as it was last month!!! :) :cool:

Steve Ash
01-13-2006, 11:29 AM
I don't have anything to add to the reason you may be expieriencing a loss to your gas mileage....I was surprised that you aren't getting more than 18. I get 18 m.p.g. with my 1969 Chevelle ....as long as I just cruise that is.

Joe Pelonio
01-13-2006, 11:30 AM
While not a mechanic by trade I've been doing most of my own work on cars since I was 14 (1966) especially on my '72 El Camino, so here's my 2 cents.

I don't know if it's every state, but here and many others are selling only oxygenated fuel during the winter. That typically reduces you mileage from 2-10% depending on the car. It can also cause driveability issues. The reason they do it is to reduce winter emissions when it takes longer for cars to warm up to normal operating conditions and when they are at peak efficiency.
If the pumps are labeled that it's oxygenated you really cannot do anything about it. If it doesn't go back up in the spring when the normal fuel returns then it's likely something else. Some of the other causes besides those already mentioned are: Leaking fuel injectors, carboned up throttle body, dragging brakes, misaligned wheels, worn wheel bearings,
transmission slippage, engine running too cold, even faulty speedometer.
Most of these condtions would not set a check engine light. Also, if you are using the defroster a lot it's like running the A/C since it kicks on to dehumidify.

Jim Becker
01-13-2006, 11:32 AM
Colder temps, different fuel formulas, etc., combined with defroster (A/C!) use will often lower mileage during the winter months. Late spring and early fall are usually the best in my experience...

Dan Larson
01-13-2006, 11:47 AM
Oh well...At least it's not as bad as it was last month!!! :) :cool:
Yeah, we've gotten off pretty easy this month. If it weren't so dang dark outside all of the time:mad: , you might be able to convince me that it's already March.

Michael Gabbay
01-13-2006, 1:07 PM
I'll check the vacuum hoses and air filter. I'm sure the air filter is clean since I checked it before I took it in so even if they did not replace it I should be ok.

Tire pressure looks to be good.

I rarely use the AC for my defroster. For the last tank I did let the car idle and warm up since the weather was not too bad.

My commute is about 5 miles with a mix of city and about 2 miles highway. Normally highway only I get about 22 - 23 mpg. And I don't have any dead bodies in the back. They are up front! :D

Thanks Guys!

Anthony Anderson
01-13-2006, 4:16 PM
Did you make sure they used the fuel efficient oil filter? If not, that can account for the 2-3 mpg fuel loss. HTH, Bill

Michael Gabbay
01-13-2006, 6:54 PM
Anthony - I've never heard of a fuel efficient oil filter. :confused:

Joe Pelonio
01-13-2006, 7:49 PM
I've never heard it referred to that way either, but since the job of the filter is to cleanse the oil of particles that cause friction, a lousy oil filter would contribute to increased fuel consumption. I don't know that it would be this noticeable just from that, but would always get at the minumum a "premium" filter and not just the cheapest one. I've never seen any test results as to which are the best.

Anthony Anderson
01-13-2006, 8:38 PM
Anthony - I've never heard of a fuel efficient oil filter. :confused:

Sorry Michael, I forgot to add the ":D ". At the parts store it is in the same isle as the muffler bearings:D. In all seriousness though, the cold temperature sounds valid. Do you park your car in the garage? Is the garage heated? You could do some experimenting to see how various conditions affects the mpg. If it were a vacuum hose, I would expect the engine to be somewhat erratic, at least sporatically. As another poster said, low or uneven air pressure among the tires could also be something to check that would definately cause a 2mpg change in fuel economy. What's the temperature in your area been when the change in fuel economy happened? Wait for the weather to break and then measure mpg. I am not a certified "grease monkey", but think simple first. Go from the easiest and start there, then rule out potential problems. Worst case a fuel/air mixture sensor could have gone bad. In that case let the dealer handle it. But rule all else out first. Do you trust that dealer? Let us know how it turns out. Regards, Bill

Scott Parks
01-14-2006, 7:41 PM
Over the past several fill ups, I've noticed that my gas mileage is off by a couple of mpg in my Honda Pilot. I've been driving the same commute to work and using the same type of gas. The only thing that has changed is I took it into the dealer a few weeks ago to get the 13K mile service (oil change, tire rotation, filters etc.).

I normally average 18 mpg, now I'm getting around 16mpg. For all of the grease monkeys, any ideas for such a dramatic decrease in mpg?

Mike

If you're in a high consumption area with smog control, your local stations sell oxygenated gas in the winter. Like clockwork every year, my 4 cylinder cars lose about 4-6 mpg! My truck isn't as picky, 13.8mpg year round. If everything is OK with your car, don't blame the cold temps, blame the gas!

Frank Hagan
01-14-2006, 11:09 PM
I'll check the vacuum hoses and air filter. I'm sure the air filter is clean since I checked it before I took it in so even if they did not replace it I should be ok.

Tire pressure looks to be good.

I rarely use the AC for my defroster. For the last tank I did let the car idle and warm up since the weather was not too bad.

My commute is about 5 miles with a mix of city and about 2 miles highway. Normally highway only I get about 22 - 23 mpg. And I don't have any dead bodies in the back. They are up front! :D

Thanks Guys!

I'm buying a Prius this month, and I've been following the gas mileage fanatic's postings at several bulletin boards. They always see a decrease of a few MPG at the first tire rotation. Seems the tires have to "break in" a bit, as the rear tires that are now on the front don't have the "edges" worn off yet.

Mind you, these are guys that are charting the wind direction and speed, and trying to figure out how that is affecting their MPG. So they are truly fanatics about it. And 2 MPG when you are gettting 50 is a smaller percentage than your 2 MPG is, but that could very well be the cause.

Jeff Cybulski
01-14-2006, 11:11 PM
Do you remember what the tire pressure was before you took it in? I'm only asking because dealers like to set the pressure around 35psi, so you get a better ride. If you had it in the 40-45 psi range ( which wouldn't be out of spec for an SUV) that probably would be the caue. I took my 96 Z-71 in for a tire rotation and they lowered the pressure to 35. It rode better then the wifes bimmer, but my mpg went down to 15 ( from 17.5). I tend to keep it around 45psi

Jeff

Jim Becker
01-15-2006, 10:01 AM
I'm buying a Prius this month, and I've been following the gas mileage fanatic's postings at several bulletin boards.

Frank, our 2002 Prius also takes a hit in the winter for mileage, but no biggie...we love the vehicle. My new Highlander Hybrid has been averaging a little over 26 mpg so far and is still "climbing". (Less than 1800 miles on it, so we are still in the early stages of break-in) Don't necessarily expect the sticker mileage from any vehicle. The Prius is "close" in the summer and it will be interesting to see if the Highlander matches that once the weather is warm. Also, these vehicles use pressurized bladders in the fuel system and tempurature affects them and the sensor accuracy. Therefore, a "manual check" on mileage once in awhile is a good idea rather than just trusting the computer.