So I have had my volvo for about a year and a half now. I live in chicago and drive to either ft wayne or indianopolis every weekend. I remember when i first got this car (62000 mi) i would get about 25-28mpg on this 3 hour trip. I put in new plugs at around 70k. While back i had engine light on for o2 sensor. Ignored it for a long time, probably 10k miles actually. Then i noticed my fuel econ was awful (20 highway). Dealership fixed it under warrenty and said it was a leaking exhaust gasket. NO improvement in fuel milage. Then i changed the air filter cuz it was filthy. Now on these trips i am still only getting 21-23 mph gallon on highway, most time i'm doing 70-75mph. Why the decrease in fuel econ? What else is there to check? No engine codes at the moment, newer tires, all at 38psi. Breaks are not dragging that i can tell. THe Kicker is that when i go 45-55 mph i get around 30mpg, but at 70mph it sucks down the fuel like crazy... am i over looking something?

one other thing i guess i should say is that at some point i did remove the muffler and put a straight pipe in it's place, so 2.5" cat back exhaust. I didn't notice fuel economy change at the time i did it though.

i run bp ultimate (93 octane i belive)

2000 c70 2.3l coupe 93k miles

Thanks for the help guys.

 

I stand corrected. On my way home from work i set the cruise control at 55... still got crappy gas milage...

 

Did you ever have your Mass Airflow replaced? I heard they had a recall on them for the 97-03 models I believe and that could effect mileage greatly.

 

Wow, what a drop. The MAF would have to completely malfunction to get that kind of misery. Do yourself a favor, replace the fuel filter, and at the same time, the fuel pressure regulator. If that doesn't work, have the PCV and air intake system cleaned out from the ground up. The engine may have stopped breathing like an asthmatic. Also, have your mechanic take a reading and see if the ignition/coil system is way off. The car is getting up in years, the cat converter may be clogged as well. At the very worst, the timing belt may have jumped a tooth, or the engine itself has a cracked head or bad rings, but this is unlikely if it's been maintained. Welcome to old car maintenance. Volvo's are worth it, though.

I'm looking into a hydrogen booster of quality, but the professional ones are so new, that the jury is still out on results vs. potential exhaust and engine wear from the added humidity. The mechanic claims I'd get 40 mpg with a turbo.

 

Ended up being a stuck brake caliper.
Better late than never on the reply...
Sold the car years ago with 185k on the clock. Saw it later with 240k miles and the new owner had trashed it