Originally Posted by TexasHonda

If you drive where there's any salt on the roads, check your fuel lines for possible leaks. They corrode and pinhole w/ exposure to road salt.

Also check the injector/fuel rail oring connections for possible leaks. You can usually smell this leak, but hands on can detect a small leak.

Fuel pressure regulator diaphragm can fail and allow raw fuel to be pulled into engine via vacuum reference line. Pull reference line and smell. If you smell gas, the diaphragm has ruptured.

OTOH, your miles of 26 mpg at 75 mph doesn't sound terrible. I think you earlier results are on high side.

I feel my 94EX (245K miles) is in good shape, and I can get slightly over 30 mpg on straight highway driving only, but closer to 25 mpg for my commute which is 16 miles w-way, w/ about 1/3 street and 2/3 interstate and variable speed. It's been that way for years.

good luck

Originally Posted by hurlingmerlin

AccorDats,

Just calculated mine this morning, and am at 26.9mpg on a 153k mile motor. that's blended city/hwy on a 5sp manual.

As suggested, measure over several tankfuls. Will change from cold temps to warmer temps as well (air density / drag).

Originally Posted by shipo

Hmmm, 26.9 mpg on a long highway trip with the 4-Cylinder engine? I'm surprised it's that low; heck, even my V6 Accord gets up near (and sometimes over) 30 mpg on long highway trips.

Originally Posted by AccorDats

Same here, i think it is low for a 4cyl 5spd manual. Like mine now, 4cyl a/t is doing almost the same. 25-26mpg crusing 70-75mph and light on the throttle. I hope the O2 will really help raise the mpg.

Im surprised because my 530i a/t,which is heavier and have lots of load on the electronics is doing 25-26mpg or sometimes better at the same speed.

Originally Posted by AccorDats

hello HAF.

so I did replace my upstream O2 sensor (denso) a couple days ago before my trip to SoCal, fortunately it resulted in gettig better mpg. I'm now getting 34-35mpg @65mph and 31-32mpg@70mph.

thanks again for the help. if anyone needs help on how to replace upstream o2 sensor on a 94-97 4cyl accord let me know, i would gladly help.

Originally Posted by shipo

Thanks for posting the update; chalk up one more lazy O2 sensor which didn't throw a code.

I've lost count how many times I've seen a report where a new O2 sensor has helped fuel economy, regardless of vehicle brand or engine. While the above may not be enough to qualify as empirical evidence indicating there's a problem with the OBD-II interface vis-à-vis lazy O2 sensors; the anecodal reports I've read are now so numerous that the possibility must be considered.