2005 Accord V6. Was getting 28 MPG highway about 2 months ago. Suddenly, I'm only getting 17 or so. The only changes were new tires in the back which I had confirmed are aligned/balanced/inflated properly, and, had the fuel system maintenance recommended at 48k miles. Still Horrible gas mileage. Any ideas? Fuel too costly to drive my Honda??

 

You can start by checking simple things such as Air filter,Fuel filter,even the fuel pump, number of things play a role in gas mileage, even tire pressure =)

 

Thats a dramatic drop, as stated above check the usual suspects. Also check your spark plugs, wires and colder temps in the morning will cause lower fuel mileage.

 

As stated, my first things to check would be plugs and filter. Also get the codes read; there might be a misfire code stored indicating a failing coil that hasn't been bad enough to light the CEL.

 

A thermostat stuck open w/ resultant low operating temps can reduce gas mileage, but I don't know if that would account for such a huge drop. Is you temp gauge at normal or lower position?

"Fuel system maintenance" sounds suspicious. What exactly was done?

good luck

 

^^^^ Florida in the summer??? I'd be really surprised, but good info for a cooler climate.

 

Sorry guys, a bit slow with replies. The receipts say, " EK-10T Ever-Wear 3-Step Fuel System Cleaner, Air Filter and Courtesy Check". In fact, I just noticed these jerks have now done this twice since I paid for it in March as well...... My mistake not looking in the glove box. No service lights on and temp gage shows normal. External temp is reading a bit high, says 99 degs when it's really 94.

So, new air filter and fuel system cleaning but doesn't say gas filter replaced. Thinking I need a new mechanic. How about changing that O2 sensor? I've read that goes bad pretty quick and can cause mileage drops?

Thanks for the help guys.

 

Fuel system cleaner is probably only something added to fuel tank. It shouldn't cause a problem. You probably paid dearly for that 6 oz of additive.

O2 sensor is a possibility. Sometimes they become slow and cause problems even though they won't set the Check Engine Light. This is fairly expensive item if you're paying shop rates for parts and labor, so suggest checking for any codes stored. Also, if you know anyone w/ an OBD2 scanner you might check long term fuel trim (LTFT). Ideally LTFT should be near zero. If LTFT is moving towards the limit, +15% I think, the CEL will likely set at some point in future. This would suggest O2 sensor may be heading south. Other things can also cause LTFT to get out of limit.

If you DIY, you can replace the O2 sensor for much less. Check ebay for replacements.

good luck

 

With a fresh oil change i can get slightly better than 300 miles per tank(City and hwy driving), when its time to change the oil i get about 260-275 thats a drop in mpgs from 21 with fresh oil to 17 with dirty oil. IDK if thats your problem, but it may be another factor you should look at. When was the last time you got your oil changed? And if you had a garage do it, are you sure they actually did it?

 

28 to 17 is DRASTIC drop. Not to question you but are you sure you are figuring th MPG correctly?