sudden decrease in fuel mileage

[vibe-a-licious]

Hi folksI'm a new member here, although I've creeped the site often to perform maintanence work on my '05 AWD Vibe.Recently I've been feeling like my mileage has dropped, so for the last 2 tanks I checked it (21 mpg and 19 mpg respectively). My past mileage was always right around 30mpg.In the past year I have changed plugs, air filter, cabin filter, front and rear diff oil(synthetic), engine oil(5W30 synthetic) and just cleaned the MAF sensor. About 3 months ago I also ran through a bottle of STP fuel injection cleaner.The car runs smotthly and at proper temp as well, so I do not think the Thermostat is bad.Any ideas?? This car should be getting 30mpg. I might as well be driving a full size pick up for 19mpg.Appreciate any help/suggestions you might have.

[Salsa Guy]

I don't know what kind of driving you do but 19-21 mpg does sound low for this car. Normally you'd expect a drop of a few when the winter fuel mix hit So for some reason your car is running rich perhaps a bad MAF or O2 senor. Have you had any codes? Proper tire pressure, correct plugs and gap? Check your air filter air box and air intake tube to make sure a mouse didn't build a home in it. (I've seen that before)

[Zimm]

winter mix gas is a likely culprit for some of that decline. did you recently put snow tires on? have you checked your tire pressure? 5 psi is good for an mpg or 2. 10 psi could cost you 5.

[vibe-a-licious]

thanks for the replys.... winter gas wouldn't account or this amount of mileage drop. No winter tires and I've confirmed tire pressure @ 32lbs. I've checked the air filter & filter box, all good. Plugs are new within 20K Kms(12,500M). Both O2 sensors are new (pre cat last year and post cat this year)....I'm baffled. My mileage has always been around the 30mpg mark even when towing or driving in the hills (BC or Alberta summer trips). I expect a few less mpg in the city, but it seems to have dropped right off the map. The car runs just as good as ever. Rpms are fine, temps are good...Just not getting as far. I can't believe this poor mileage. I really love this car, as it meets all of my needs, but this mileage is ridiculous.

[Zimm]

if it's only been 2 tanks, is there any chance you bought your gas at a different station than usual? or maybe your usual station got a shipment of crap gas. stranger things have happened. although it hasn't happened with this car, i have gotten a few bad tankfuls over the years, resulting in terrible performance, mileage, or both.

[djkeev]

Don't know what engine you have but check if the VVT filter and assembly are clogged up with gunk. If this doesn't work, efficiency will plummet.Dave

[keithvibe]

If you were getting 30mpg in city driving. You must have a one off vibe. Hwy driving, sure 30mpg is normal. City, 23-26. I have personally got 19-17 mpg now and again. It was usually because I drove hard. 1. Don't let the car idle for more than a minute before driving. 2. Keep your rpm's below 30003. Take your 32psi and toss that out the window. Run 38-40, I have been doing that for 5 years with out abnormal tire wear. 4. Take out all the excess weight. 5. If you say everything is working fine and if you still have the issue after replacing the filter Dave suggested then sorry to say you need to adjust your driving.

[vibe-a-licious]

engine is a 1.8 L 1ZZ-FE I4 - only choice for the AWD in '05 I believe. I'll definitely change the VVT filter - can't hurt - she's got 130K kms(82K Ms) and I'm sure the previous owner didn't do it, and I can't think of any other maintanence I've not done that would help.As I'm sure you know, the AWD's have a smaller fuel tank, so when mileage changes you notice it rather quickly how often you visit your filling station.I'll also push the tire pressure up 5 lbs as well, should see some gain there.Cheers

[Salsa Guy]

Yea that VVti Filter is a PITA if you have a SC on.

[themrfreeze]

If they use as much salt on the roads up there as they do here in western NY, it could be an issue with the brakes dragging due to corrosion. I've had a number of cars with rear discs develop this problem, and if you don't get the calipers cleaned and lubed every year or two, it'll both decrease your MPG and your brake life. Easy enough to check...just get the rear wheels off the ground and see if they spin freely.

[star_deceiver]

And driving through snow and slush uses a lot more fuel then a smooth, plowed road.

[leemur]

Over filling the tank can cause the charcol/evap caontainer to get soaked and lower mileage...or so I've read. I think that happened to my 04 in the past.I also went to 100% gasoline and got much better mileage.

[j42.snyder]

For those who seem suspicious of the mileage posted, keep in mind that here in Canada we used to use Imperial gallons for reference (5 quarts/gal not 4), so that really skews any "MPG" ratings between our countries. Since we changed to metric over 30 years ago, fewer people still use gallons for reference, and probably aren't aware of the difference. This will also explain why he's so upset with the 19mpg from recent times, as I believe that's only about 15mpg in the U.S.A.I would also check for dragging brakes. Simply feeling the temperatures of the wheels immediately after a drive may be an easy check for this problem - depending on just how cold it is. Keeping idle time to a minimum is helpful as well, as that produces 0MPG (or an infinite number of L/100km in the metric world). Many people around here seem to make plenty of use of their remote starters...If that all checks out okay, I'd be tempted to look into the AWD system, although I wouldn't expect it to make that drastic of a difference. Like star_deceiver mentioned though - road conditions can have a drastic influence as well, although I haven't been following Winterpeg's weather reports lately. We've been pretty lucky down here in Southern Ontario so far - no accumulation to date!Keep us posted.John