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Discussion Starter #1
Alright so my 05 mdx is getting pretty ****ty MPG, between 10-11 city and I try my best to be light on the peddle, but when I do that it's still bad. One of my co workers told me to use a fuel injector cleaner so I was going to get chevron techron but Home Depot only had gumout so I settled for that.

Now before I used gumout, I used to fill up about every 12 days, almost two weeks. Nothing has changed, if anything like I said I'm trying to be more light on the peddle, after gumout I'm filling up every week. Once again, nothing has changed! Same driving conditions! It's insane. I just filled up on Sunday and didn't drive anywhere, on Monday I drove to work, about 26 miles round trip and today I picked up my girlfriend and we went out to eat, probably added another 15 miles and already my gas is saying I've almost used a quarter tank.

I purchased chevron techron with this previous fill up that I got on Sunday and I'm waiting to use it all up with my tank and see how that goes. Anyone knows why I got a sudden drop in gas?
 

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I am sorry, but you cannot tell anything without written gas mileage tracking, averaged over may miles. You need to average it over many tank fulls of similar driving. For example even my weekly commute totaling about a tank full per week, on the same route, with similar driving habits will change a MPG here and there, over a tank full. The mileage computer is also often inaccurate, and I know we all think we can just tell, but unless you have had MAJOR changes in mileage you cannot "feel" a 1-3 MPG change just by watching the gauge. The only possibility I can come up with, is the injector cleaner has dislodged other particles and they have collected somewhere such as the fuel pump strainer, or injector inlets, that now restricts flow to the injectors, causing mileage issues. It's entirely possible you got some old gas, and it just doesn't have the BTUs that you normally get, resulting in a perceived change that really has nothing to do with the injector cleaner. Hang on and keep driving it, unless it gets drastically worse, and won't run, I have a feeling you will return to more normal "feel" next week.
 

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Discussion Starter #3
Well I am going based off my refills. Usually takes me about two weeks to refill my tank (12 days) and now its taking me about a week, and nothing has changed in my driving, nor my driving routine. Just real weird seeing your gas go down that fast.
 

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Discussion Starter #5
Yah I am currently in the process of doing that. I clocked my mileage before I filled up my car with chevron techron (which is was 2 tanks after the gumout fill up. So I put gumout with gas, then let it finish, put gas again without anything, let it finish again and then put chevron and gas).
 

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Discussion Starter #8
So when I used Chevron Techron I started with 93557 miles and I refueled at 93740 miles with 18 gallons. So If my math is correct I got 10.1 mpg. Also I had like 15 more miles left on my trip computer, if that means anything.

I just feel like this is so low. Why does my car burn so much gas? It is mostly city driving, but I am not hard on the pedal at all.
 

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Fuel blends in different states change (many go to more ethanol in the summer - don't even get me started on THAT scam). Also, you are likely running the A/C more than you used to, and might be letting the car cool off (I know we do, but we live in an area that's the approximate temperature of molten lead). The A/C will burn a lot of extra gas, especially around town. Also, get a new air filter - hands down the best thing to do if you notice your gas mileage slipping... they're cheap, easy to change, and could make a pretty big difference if your old one is dirty.
 

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If you can access a scanner w/ tracking of car data values, check the Long Term Fuel Trim (LTFT) for trends. Normal is +/- 5% or lower. High + LTFT (> 5%) indicates the PCM is adding fuel to compensate for a perceived lean condition. It could indicate intake air leak or possibly faulty A/F sensor. Advanced diagnostics req'd to run fault to ground.

Poor valve gap can result in performance issues, but usually causes missing and rough idle. DTC's would usually be set.

OTOH, a fuel leak will cause poor gas mileage and engine runs fine. Look for leaking fuel injector/fuel rail connection, corroded fuel line, fuel tank leak.

If your figure of 10 mpg is accurate something is wrong. I got better than this towing a 21-ft boat recently.

good luck
 

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Discussion Starter #11
If you can access a scanner w/ tracking of car data values, check the Long Term Fuel Trim (LTFT) for trends. Normal is +/- 5% or lower. High + LTFT (> 5%) indicates the PCM is adding fuel to compensate for a perceived lean condition. It could indicate intake air leak or possibly faulty A/F sensor. Advanced diagnostics req'd to run fault to ground.

Poor valve gap can result in performance issues, but usually causes missing and rough idle. DTC's would usually be set.

OTOH, a fuel leak will cause poor gas mileage and engine runs fine. Look for leaking fuel injector/fuel rail connection, corroded fuel line, fuel tank leak.

If your figure of 10 mpg is accurate something is wrong. I got better than this towing a 21-ft boat recently.

good luck
Thanks will check it out.
 

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Alright so my 05 mdx is getting pretty ****ty MPG, between 10-11 city and I try my best to be light on the peddle, but when I do that it's still bad. One of my co workers told me to use a fuel injector cleaner so I was going to get chevron techron but Home Depot only had gumout so I settled for that.

Now before I used gumout, I used to fill up about every 12 days, almost two weeks. Nothing has changed, if anything like I said I'm trying to be more light on the peddle, after gumout I'm filling up every week. Once again, nothing has changed! Same driving conditions! It's insane. I just filled up on Sunday and didn't drive anywhere, on Monday I drove to work, about 26 miles round trip and today I picked up my girlfriend and we went out to eat, probably added another 15 miles and already my gas is saying I've almost used a quarter tank.

I purchased chevron techron with this previous fill up that I got on Sunday and I'm waiting to use it all up with my tank and see how that goes. Anyone knows why I got a sudden drop in gas?
Replace the engine air filter every 30K miles. Dirty one makes your car make less power and use more fuel. What's the mileage? Replace the spark plugs every 100K. How's the transmission fluid? It should be a pinkish red. Brown means it's burnt and your trans isn't able to put the power down on the road.

Also make sure you are using 91+ octane. Using anything less makes the engine pull timing thus causing more fuel to be used.
 

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Discussion Starter #13
Replace the engine air filter every 30K miles. Dirty one makes your car make less power and use more fuel. What's the mileage? Replace the spark plugs every 100K. How's the transmission fluid? It should be a pinkish red. Brown means it's burnt and your trans isn't able to put the power down on the road.

Also make sure you are using 91+ octane. Using anything less makes the engine pull timing thus causing more fuel to be used.
Bought the car with 907xx miles, currently at 938xx. When I bought it I used nothing but 93 octane and I did a oil change, changed the tranny fluid, changed the filter and a/c filter, replaced front and side motor mount, serpentine belt, and spark plugs. Original owner changed the timing belt.
 

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You can try changing the PCV valve (dead simple--should take you 2 minutes, half of which is spent locating it--and cheap; you can also pull it out and inspect it yourself, just shake it and make sure it still rattles, but honestly, it's so cheap that you might as well replace it while you have it out) and/or the EGR valve (more expensive, not much more difficult, it might be enough to take it off and clean it out with some carb cleaner to free up any deposits). Both of those affect MPG.

While you're under the hood, make sure that the air intake hose isn't cracked or something. Good luck.
 
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