Really, really poor gas mileage: 15 U.S. mpg

[buldir]

I live in Anchorage, Alaska and the traffic is typical stop and go, rarely travel faster than 45 mph, the roads are rough, I have studded tires, it's relatively cold (10-30 F) lots of braking, etc. -- a real nightmare for a car. I have a 2005 AWD and usually get between 21-26 mpg (U.S.) in town, which is not too bad considering the circumstances listed above. I recently took the car up to Fairbanks and back (715 miles round trip) and averaged about 70 mph. During the trip back (with a tail wind), I got about 31 mpg (U.S.), which is nice for an AWD Vibe. Here's the issue. When filling up in Anchorage after the drive back, I filled up the tank and could only put 10 U.S. gallons in, despite the fuel gage being well below empty (in the black). I found this odd since I can normally put in 11.5-12 U.S. gallons when very empty. Now, I've gone through a half a tank and have only traveled 95 miles...that's about 15 mpg! That's bad.Tire pressure is fine -- last oil change was synthetic about 5800 miles ago. I am going to get the oil changed this week. I have read several other posts related to gas mileage already, but none of those posts mention anything lower than 18 mpg. Should I try the Techron cleaner? What about changing the transmission fluid? Any thoughts would be most welcome. Thanks.

[bodhi_tree777]

wow, that's strange. I'd almost wonder if there wasn't something wrong with the sensor in the fuel tank (or float or whatever it is) that detects the level. I'm sure someone here will chime in with a more specific answer. g/l

[northvibe]

yes theres something goofy with that....Its like a "13" gallon tank so yes below empty on the gauge and you should be able to fill around 12. I almost agree with bodhi, seems like a fuel level sensing issue.When you filled it up with the 10 gallons did the car say the gas was above F?

[djkeev]

I wouldn't worry until you fill it up, do a trip and fill again, preferably at the very same pump and compute your mileage.I too am thinking something is wrong with your gauge system.Verify what exact mileage you are getting first, ignore what the gauge is telling you, what really is in the tank is important. (don't ignore the gauge so much that you run out of fuel!!)Let us know. If the mileage is really down, first thing I'd check is dragging brakes and tire pressure. You might have a check valve sticking (frozen?) in the brake system not allowing a complete piston pull off. Remember brake fluid absorbs moisture over time, while brake fluid is hard pressed to freeze, water freezes easily. That is why brake fluid replacement is a good idea and recommended by many at certain time intervals, especially in the environment you live in. That moisture also causes fluid compression issues as well as rust where rust should not be.Dave

[engineertwin2]

Quote, originally posted by buldir »When filling up in Anchorage after the drive back, I filled up the tank and could only put 10 U.S. gallons in, despite the fuel gage being well below empty (in the black). I found this odd since I can normally put in 11.5-12 U.S. gallons when very empty. Now, I've gone through a half a tank and have only traveled 95 miles...that's about 15 mpg! That's bad.One tank won't make a good projection. I agree that it isn't good, but it's possible that the pump was having problems, and you really did wind up 1.5 to 2 gallons short. That would put you back into range.I wouldn't worry until you had 4 or 5 consecutive tanks at 15 mpg.

[jake75]

I rarely let the tank get more than 1/2 empty - but the one or two times I I have run ti to where the low fuel warning come on it still only takes 10-10.5 gal to fill.

[2002sportside]

Quote, originally posted by engineertwin2 »One tank won't make a good projection. I agree that it isn't good, but it's possible that the pump was having problems, and you really did wind up 1.5 to 2 gallons short. That would put you back into range.I wouldn't worry until you had 4 or 5 consecutive tanks at 15 mpg.That is my guess, pump problems... I very rarely get my work van to actually fill the tank - Shell and Mobil seem to be the worse.I wouldn't worry until it is on multiple tanks...

[buldir]

Wow. Thanks for all of your great comments. As a scientist, I was also thinking that I should wait and see if this continues after consecutive fill-ups. If I can only put in 9-10 gallons when empty, over multiple fill-ups, it's likely a fuel gauge issue. When I did fill up the car with the "bogus" 10 gallons, the gauge did say full. This fill-up occurred *well after* the empty light came on...the gauge was literally 1/8 inch below the "empty line" in the black. It also seems the fuel gauge "jumps," rather than smoothly move down to empty over time. In other words, the gauge remains on half a tank for a while, then, after some time, all of a sudden shows 1/3 tank left. I could just be losing my marbles though.Of course, what I could do is not trust the gauge at all, keep a 5-gallon jug of gas in the trunk, and run it until we stop, noting the mileage on the trip odometer!