n3ok318

iTrader: (1)

I've never complained about gas mileage on my tsx. I have gone over 500 miles numerous times before and mpg always stayed above 30mpg as I drive 90% freeway. But, after 50k, my gas mileage is going down day by day. I average about 24-26mpg and my driving habbit hasn't changed, nor my daily route. I don't carry extra weight or anything. Anyone else having same problem? I hope it's the weather that's causing it but my car has given me constant 30mpg past two years.

Sigh, I wish there's no more problems ahead

SodaLuvr

Usual checks under such situations:

1. Is the tire pressure correct?

2. Any recent change in driving style?

3. Engine Air Filter been replaced?

4. A bit early, but check the spark plugs. If necessary, drop it four new NGK Iridiums for about $40.

5. Any Check Engine Light?

xenonhid

What kind of Gasoline are you using? Brand + Octane,

Mokos23

Should I worry? I'm about to hit this plateau soon. I just hit 48,000 miles this morning.

micvog

Did you just replace your tires? I only have 39K miles, but after switching from OEM to Kumho Ecsta SPTs, my mileage went from ~29 to ~25 with everything else the same.

SodaLuvr

Yeah, some tires do have a greater rolling resistance than others, and new tires will cause your mileage to suffer quite a bit sometimes.

dwest1023

Are you using gas with ethanol? That stuff burns like water. Try a tank of Chevron or BP and see what you get.

PACman

O2 sensor could be going, but a CEL should show up if it does.

Tangoman

All oil companies sell gas with 10 percent ethanol (including Chevron and BP)....

My 04 TSX has 53,000 miles on it, and I have gotten up to 32 miles per gallon on the highway.

davidspalding

• Has all scheduled maintenance been done?
• Have you changed gas brand?
• Do you run the a/c more? Or ... have you had the cabin air filter changed in the last year (a clogged filter makes the HVAC work harder, I'm told)?
• Are you running on OLD tires, aside from checking the cold air inflation?
• Have the tires been rotated and balanced recently (within last 6000 miles)?

dwest1023

Not in my area. It is suppose to be posted on the pumps if it has ethanol in it. In my area Texaco, BP and chevron do not use it.

Tangoman

I stand corrected....

Well, then I should say that all I have ever been able to use is 10 percent ethanol, and I get 32 mpg on the highway (53,000 miles).

n3ok318

iTrader: (1)

Hmm.. all maintenance has been done and I use Shell 91 Octane only and I've been using it since I bought the car. Believe it or not, my gas mileage does not change much even if I have full AC on all the time (maybe 1mpg at most) and I changed AC filter around 50k.

Along with the filter, I changed all my tires. And yes, I changed them at 50k. They're Yokohama so they aren't stock. I think it's the tires causing the drop on gas mileage. Argg.. They perform so much better than stock. But I guess in exchange, it gives bad mileage.

davidspalding

Bingo. Different tires can effect MPG, I'm told. If you get better performance than Michelins or Nexens, then the trade-off is probably worth it. Particularly if you experience less tire-road noise. I hear that complaint regularly.

How was your cabin air filter? I'm thinking of starting a thread of "worst HVAC filter" photos. Some wait the whole 30,000 to change, and I can only imagine the filth that's in there.

n3ok318

iTrader: (1)

Well, I changed mine at 50k for the first time and it was very clean.

I heard horror stories about them being extremely dirty, but mine was so clean that I could've use them again after shaking the dust out couple times.

But I used new one since there might be hidden micro dusts

visuelz

Give them more air =]

csmeance

if you want to get better MPG, run some seafoam through the car. in any gas car, there will be some buildup of carbon and gunk in the motor, seafoam helps get rid of it and works well.

CarbonGray Earl

I think its the tires. I changed mine at 48k and that's when my mileage changed. I thought it was because I was driving faster with my new setup. I went from a consistent 26+ on my drives to a 22-23.

davidspalding

Cabin air filter? Unless you've been driving in a clean room, the more likely explanation is that your cabin filter has been changed out during periodic servicing,* and you haven't noticed it on the service invoice. You may also be driving in a relatively smog-free area, too; lots of rain may cut down on ambient particulates, too. (David thinks wistfully of WA and OR.) Since I'm beginning to suspect the Acura and Honda/micronAir filters are near -HEPA quality, stuff that didn't shake out is just as prevalent.

*Can't say which one, can't read the online manuals from Linux at work. Guessing ... 20K and 40K?

n3ok318

iTrader: (1)

Hm, maybe mine's different from all others?

My friend changed it along with me (he civic with 30k miles) and it was filled with small yellow dusts. But mine on the other hand was so clean, just some pieces of scattered leaves.

And NO, Acura wouldn't have changed them for free because I paid $35 for oil change and nothing more all the time.

davidspalding

Who said anything about free? ("Free" and "dealer" are rarely used together in a sentence.) Some of the periodic maintenance visits have a whole slew of items. Are you telling us that over the 50,000 mile lifetime of your car, you've only changed the oil? Did you buy this car new?

What I'm driving at is that there is another reason why your last cabin filter was "so clean that I could've use them again" than it just wasn't getting dirty. Could be your environment, could be the result of a prior servicing, or ... I dunno, maybe you guys hve little Cabin Air Filter Fairies up there who change filters during the nighttime. Boy I wish some of those CAFFs would migrate south....

Tsx536

This could be the problem. Sporatic idle can be an indication if you don't see a CEL. You can also try hooking up an ODBII tool that can see your a/f ratio. 14.0 instead of 14.7 at idle is an indication that the O2 sensor is going bad and the ECU is going into limp mode. This richer a/f ratio will lead to reduced gas mileage.