arracado Posted May 14, 2005 Share Posted May 14, 2005 I've been trying to help the MPG of our 97 OBW. In stop/start city driving, I'm averaging 20 at best, but it's more often than not 17 or 18. I'm lucky to get 200 miles out of a full tank. Changed the air filter, plugs (NGK Platinum), fuel filter, coolant. No change. The funny thing is, the car runs beautifully. No hesitation, no hard starts. I just get crappy MPG. I've been reading through threads, and many mention the O2 sensor being a cause for poor MPG, but like I said, the car runs fine otherwise and I've never had the CEL come on. Could the O2 sensor still be faulty? '97 OBW 2.5L Automatic Quote Link to comment Share on other sites More sharing options...
Olnick Posted May 14, 2005 Share Posted May 14, 2005 What's your mileage? From what I understand, they do "weaken" with age--may not be apparent in driving but could affect fuel consumption. I don't think a weaking O2 sensor would throw a code until it's really bad (could be wrong though.) Just changed mine recently and am hoping the mpgs improve! Quote Link to comment Share on other sites More sharing options...
arracado Posted May 14, 2005 Author Share Posted May 14, 2005 What's your mileage? From what I understand, they do "weaken" with age--may not be apparent in driving but could affect fuel consumption. I don't think a weaking O2 sensor would throw a code until it's really bad (could be wrong though.) Just changed mine recently and am hoping the mpgs improve! 125K miles. I knew I was forgetting something. I don't know how much longer I'll keep the car if I can't get some kind of improvement. 18 MPG for a 4-cylinder engine is ridiculous. I might as well be driving an SUV (not that I ever would), but with the way gas prices are I think I'd be just as happy with a 2.2L Legacy wagon that got better miles. Quote Link to comment Share on other sites More sharing options...
Olnick Posted May 14, 2005 Share Posted May 14, 2005 I drive a 2.2L--'95 Legacy L wagon AWD with 5-spd manual, 106k miles. Averaged 21.7 mpg over the last 8 months in nearly 100% stop-and-go city driving. Maybe that's the best I can expect. AWD will never make for super economy. Then I fondly think back on my '85 GL--2WD, sweet little 1.8L, 25 to 27 mpg in virtually the same driving conditions! Quote Link to comment Share on other sites More sharing options...
The Dude Posted May 15, 2005 Share Posted May 15, 2005 Check your mileage on your next highway trip. Highway driving has a lot fewer variables than the city, and gives you a truer measure of your car's mpg. If your highway mpg is OK, there is probably very little that you can do. It probably is NOT the problem, but a bad coolant temp sensor can also cause a loss of mpg. If you can get a good scanner, you can check the actual voltage/operation of the 02 sensors. I would guess that your mpg is normal for city driving. Quote Link to comment Share on other sites More sharing options...
gillans Posted October 5, 2005 Share Posted October 5, 2005 I've been trying to help the MPG of our 97 OBW. In stop/start city driving, I'm averaging 20 at best, but it's more often than not 17 or 18. I'm lucky to get 200 miles out of a full tank. Changed the air filter, plugs (NGK Platinum), fuel filter, coolant. No change. The funny thing is, the car runs beautifully. No hesitation, no hard starts. I just get crappy MPG. I've been reading through threads, and many mention the O2 sensor being a cause for poor MPG, but like I said, the car runs fine otherwise and I've never had the CEL come on. Could the O2 sensor still be faulty? '97 OBW 2.5L Automatic I know how you feel i have the same model and get the same fuel consumtion. changed o2 sensor and it made a good differance to performance but not much change to the fuel. I'm thinking of not looking at the fuel gauge any more to see if i feel better. Quote Link to comment Share on other sites More sharing options...
friendly_jacek Posted October 5, 2005 Share Posted October 5, 2005 I'm in the same camp. 16-18 MPG in city only. But 23-25 MPG hwy. 2000 Legacy wagon. Service by the book, 56000 miles on it now. I tried a lot of things. I keep 40 PSI in tires, all synthetic fluids, checked all sensors via OBD2, all nominal and readings are real (ie corresponding to ambient conditions). O2 sensors work well; replaced front anyhow, no change. The only consistent abnormalities I detected was fuel pressure above nominal and negative long term fuel trim. Replaced the fuel regulator to find no change in the pressure or fuel trim! My hypothesis is that some subaru fuel regulators are defective and replacing with subaru part doesn't guarantee anything. One of these days I will try aftermarket variable pressure fuel regulator, but now I will just scrach my head in disbelieve. Quote Link to comment Share on other sites More sharing options...
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