I have a 2008 Honda accord with 108,000 miles. Four cylinder auto trans. Everything I've read says it should get 31 mpg hwy and 24 city. I'm getting 20 city and 24 hwy. new tires with correct air pressure and I drive like my grandma. I traded an H2 hummer for the Honda so the mileage is still a gift but it should be better. The car runs great with no issues. Any ideas?

 

any recent service done on the car? 24mpg is not bad and not good either, its just okay. thats only from my experience. im getting 32-36mpg hwy on my 96 accord 184,000 miles

 

20/24 is pretty low, even for an auto trans. Now you can first begin checking for reasons outside the car itself...

1) You already said you're driving conservatively, we'll take your word for it.

2) Do you live in the mountains? Sometimes bad mileage is inevitable if you don't live near flat land.

3) I think it calls for new sparkplugs at about 105k miles. Know if that's been done? Use NGK or Denso plugs, I've heard people say Hondas run badly on Bosch or some other brands, but can't vouch for that firsthand.

4) Brakes dragging? After driving, check whether any wheels are especially hot. It's normal for the front to be hot, but you'll have to judge whether it's excessive. A good test for dragging brakes is a flat parking lot, shift into neutral & coast at a lot slower than walking speed - does it drag to a stop? Best test for dragging brakes is lift the car (safely supported) & spin the wheels.

5) Auto transmission fluid: Amount OK on the dipstick? Color? Smell? Hondas DO NOT like to be power-flushed. You should drain & fill the trans with only Honda brand ATF. Not especially cheap, but lots of people report poor running with other fluids that say "compatible" or "for Honda". Again, not firsthand because I've got manual transmissions.

 

Thanks for the advice. Going to install new spark plugs and service the Trans this weekend. While its on stands ill check for brake drag. Thanks again!

 

Is this perhaps a V6? The V6 will not get 31 mph on highway IMO. I would guess 26-28 would be tops unless you're driving on perfectly flat ground w/ no wind.

good luck

 

check you pcv valve, air filter, and of course tire psi also!

 

Hmmm, I guess someone forgot to tell my 2001 V6 EX, it seems to get closer to 33 mpg on the highway at ~72 (and trust me, it ain't flat here in New Hamster).

 

i accelerate quickly (rev to 4-5k typically) and over the past year I average 29mpg combined.

BMW released their E series in the late 80's with the 325e. these engines were developed for economy and they relied on high torque and low revs. The idea (and it works) is to accelerate to cruise speed quickly (70-80%) throttle, then coast. According to the research they did (I'm trying to dig it up) they discovered that by taking longer to accelerate you are bringing average MPG down anywhere from 10-20%


Try resetting your ECU, check your spark plugs and other basic maintenance. Is there any check engine light?

 

Silver6gen, that reminds me I remember something that BMW did a long time ago. It wasn't SIMPLY accelerating quickly. It was using low RPM and more throttle. Maybe that was their trigger for developing the "e" engines.

Short story is they got good MPG by using 70% or 80% throttle, but at real low RPM. Like maybe shift at 2000 rpm. Automatic transmission won't let you do that, because it'll downshift when you give it 70% throttle.

Disclaimer... IIRC, this was for better MPG, not necessarily for better engine lifespan.

Still, I think you can over-do the conservative driving. I'm not talking smoking burnouts, but just idling away from a stop might be too far in the other direction. We can only guess what you mean by "driving like your grandma".

The long story:
A nearly-closed throttle is a huge waste of energy. So the imaginary "ideal" engine would be one that would magically change displacement while operating at large throttle-openings all the time. Say you're accelerating from a stop; you want a 2.3-liter engine operating at 80%-open throttle. Then say you're cruising at 65, you need about 10 HP, so what you want is a 0.23-liter engine operating at 80%-open throttle.