Hi All... The original thread is here. http://wrxatlanta.com/forums/showthread.php?t=12523 I was thinking about bringing the car to the dealership, but would be interested to know if anyone in the community has tracked down MPG problems that could be related to the O2 sensor, air filter, oil filter, maybe even spark plugs... Otherwise, I'd appreciate any mechanic recommendations. For some reason, I'm not so sure Royal Subaru (Decatur) will have the interest to figure this out. They kinda gave me the "Are you SURE you're MPG is dropping? There are many things that affect MPG." comment. It's fair, but I'm almost certain something is wrong now... Thanks in advance.
how many miles are on the car? Have you changed the fuel filter? Have you changed your air filter?Have you changed your oil and filter? Have you cleaned your injectors? Have you reset your ECU? Has your commute changed (stop and go vs continuous speed)? Are you driving more aggressively? Have you checked your tire pressure? Have you added any new mods?
Yep. That's the first thing I checked. Tire pressure is good. I generally run 34 psi fronts and 32 psi rears.
Some of this info is in the thread link above, but it's worth repeating here. My car is an MY04 WRX wagon totally stock except for tires which were changed after beginners autocross with Siegel Racing (fun fun.) I’m a car idiot so all the work is pretty much done at the dealer. Odometer: approaching 20,000 mi Fuel filter: not changed to my knowledge Air filter: not changed to my knowledge Oil and filter changed at last service in January at 18,719 mi Injectors: not cleaned to my knowledge ECU reset: nope. Commute change: Same commute since I’ve owned the car. It’s all city driving, about 8 miles round trip. When commuting, I drive like a granny. Tire Pressure: checked. It’s been good for the last 3 tanks/3 months as I’ve watched the situation. Mods: none Thanks… I really appreciate the comments you’ve all made. I kinda don’t want to just go to the dealer and give ‘em such a vague problem as “My MPG has dropped by 15-20% in the last 3 months since my oil change.” If I can rule some things out ahead of time, maybe I can get them to zoom in on the potential problem. Here’s the car's service history… 3/15/04 @6mi for Recall for cruise cable clip 9/3/04 @435mi for Repair / replaced SOP O2 sensor 3/12/05 @3,653mi for 3,750 Mile Service 7/6/05 @6,476mi for Repair / replace expansion valve and keyless entry buzzer 7/7/05 @6,476mi for Repair front left wheel skirt 8/31/05 @7,588mi for 7,500 Mile Service 1/25/06 @11,182mi for 11,250 Mile Service 6/18/06 @14,396mi for new tires Kumho ASX balance and alignment 6/20/06 @14,438mi for 15,000 Mile Service 12/27/06 @18,248mi for Repair of rear quarter panel 1/27/07 @18,719 for 18,750 Mile Service PS I just passed my emissions... Thanks in advance for any suggestions.
pop the hood, then open the air box(2 pop latches). It will have enough room to pry open the box enough to get the filter out. If it's dirty then get a new one.
metro ATL gasoline mixture changed? I just had an interesting conversation with the dealer summarized here http://www.wrxatlanta.com/forums/showthread.php?t=12523&page=2 the quick summary is that he thinks the new fed regs governing fuel mixtures that went into effect Nov 06 and Mar 07 in ATL may be causing some of the problem...
mines an '04 too and i've noticed no difference except in the summer when i run the ac. i generally get right at 21.5 with a heavy right foot
i have been told there are different additives that are put into the gas when it is summer and winter time. maybe this has an effect. maybe the car has to relearn the computer to adjust to the mixtures. i have heard alot of complaints about this also. not really much the dealer can do without any check engine lights, because they dont really have anything to go off of.
yep. that's some of the advice i got off of nasioc as well as EPA. states usually do change formulation in the colder months, but it shouldn't yield a drop of more than 2 MPG or so... also, i've had the car for over 2 years now and i don't recall last winter having the same issue. thanks for the post...
Seeing a lot of 10% ethanol signs going up here recently. I have yet to notice a significant drop in mpg though.
My RX and my Wife's WRX is still getting in the low 30's on the hwy... Bring it up to SOG and the worst you'll be out is $50 for a diag fee....request me (Will) and I'll give it a close lookover and take it for a drive with the Select Monitor.
water in gas at shell gas stations. ok guys, just got this memo from my service manager. several shell gas stations in the atlanta area were "locked up" over the weekend by the STATE OF GA. because there was significant water contamination in their gas tanks and was gas they sold. if you have any unusual driveabilty concerns and you have filled up at a shell gas station in the atlanta area this may be part of the problem. i was told that a car is at jim ellis with a significant amount of water in its gas tank, and they had just filled up at a shell gas staion over the weekend. hopefully this is not your prolem, but if it is i am told that shell gas station will reimburse you for repairs that may need to be done.
I changed the stock air filter with a K&N filter. That looks like it may have solved the problem. My last tank was 232.3 miles / 10.916 gallons = 21.28 mpg About 130 of it was highway miles though. The newest tank seems to be bearing out what I'm used to seeing. It was all highway miles for the first 130 miles. When the first part of my tank was all highway miles, I remember that the needle usually dropped to the first quarter tank tick mark at around 120-130 miles. So this may be a case of me not realizing how much I really normally got in ALL city driving and then add to that a dirty air filter. Thanks everyone for your help.