Another bad gas mileage thread

[KITT222]

Well, I think it is about time I do one of these. Sorry, yes, it's another, but I have followed the word of others, but nothing seems to work. I have: checked my tire pressures (they're all good), changed the oil (another change coming up soon), replaced the VVT filter, cleaned the MAF, it has gotten warmer here, I have a heavily conservative driving style, and I think maybe a few other things and STILL I'm getting 24-26 mpg. I don't know what to do. This genuinely depresses me. I have tried to much to get my MPGs up, but it's all futile it looks like. Anything that can help, please, I'll try. Thank you.

[star_deceiver]

I'll state the obvious first... Make sure you're driving around in overdrive and not 3...When were the spark plugs last changed? Have you tried seafoam?

[KITT222]

OD = on, I've run a bottle of HEET through the gas tank, and I have no idea about the plugs.

[jake75]

24-26 is all I ever get but a lot of short city trips.

[blindman10]

Any codes?How many miles?Has it been like this since you owned it or has it slowly declined?Any engine modifications?Along with what jake75 said, is that 24-26 city driving? Highway? Mixed?I think for mostly city driving 24-26 would be acceptable. If that is mostly highway, something is wrong.If you still feel something is wrong, not knowing the mileage of your vehicle or maintenance history, I would:-check/replace PCV valve-check/replace air filter-replace the plugs (NGK or Denso Iridiums)-run a quality fuel system cleaner once or twice (like Techron)-clean the throttle body-clean the MAF and IAT sensors-along with VVT filter, clean and check operation of oil control valve itselfI am also working toward improving my MPG as much as possible. Having just bought my car at 70k without any service records, I've done or am planning to do a lot of the same as above. I also will be cleaning my intake manifold (because there is a ton of oil in it) as well as replacing the intake manifold gasket with Toyota's newest version to avoid the all-too-common idle issues due to this faulty gasket. These steps may not do anything for my MPG, but should help the general health of my engine.

[KITT222]

No codes, almost 83,000 miles, been like this since I bought it last November (got a little better after I cleaned the MAF sensor), totally stock engine. My driving is suburban, I call it. Nice longish roads with speed limits of: 45-55mph on my daily route with a few stoplights in between, but I do try to avoid lights. Air filter is good, I know that. We have yet to check the plugs, and the PCV valve, but I think it'd be worth it to give 'em a look. What is an IAT sensor?I'll pass that list onto my dad and see what ends up happening. Thanks!

[yyamad1]

Well I would suggest you change the upper O2 sensor, even though you have no codes it could still be reading very slowly giving you bad mpg. Ive done alot to my vibe but in Chicago traffic/city/highway driving, Im getting 30-32 per tank and occasionally see 37-40 on 25miles trips. I do mainly short trips too, in Denver CO suburban driving, I was getting 35-36 per tank. Vibes aerodynamics can be improved alot and so Ive been working on that...

[jkm311]

I know this sounds strange, but... I don't consider your numbers to be *that* bad. If you're hitting lights every other mile or so on "Nice longish roads with speed limits of: 45-55mph" this is the *average* mileage I would very much expect.The only way you're going to hit 30+ MPG consistently is spending more time on a highway without stops, at 60-65 MPH. If you were in the 20-22 range, then I would worry. Have you had an alignment lately? If your tires have any sort of issues (not properly making smooth, straight contact with the road), that might be a source of inefficiency.Sounds like you've covered or will cover everything you possibly can. Good luck, but I would be surprised if you can see more than 30 MPG, given the roads you typically drive the most.Last ditch effort: How low do you let the fuel gauge get before crunching the numbers? Or do you have a separate fuel MPG gauge you're running? You might not be accounting for the actual fuel used. Half a gallon can throw off your estimates.

[KITT222]

I do occasionally have some freeway driving, actually. I go by my gauge (which never seems to be too low for too long) to drive efficiently, and I refill at .5-1 gallons left, so I go by both sort of. And speed limits are optional, especially when traffic is flowing at about 60mph. yyamad1: it is important to note I have an automatic. I'm not sure what you have, but those are closer to what I what least want. Well shoot. Off to more intensive tactics for MPGs. (MPG>MPH IMO)

[09vGT]

I only average around 24. It depresses me too. Especially since I really like power; I had been driving a Cadillac CTS in place of my car for a couple of days and averaged 22. It has almost 100 more horsepower.

[bassplayaz06]

honestly, here's a suggestion... get a manual or a GT. they have better gas mileage. oh and my grand dad has a Pontiac G8 GT and averaged 28 mpg from the special fuel saving system where it shuts off 4 cylinders. it weighs more, and has a bigger engine and gets better mileage than i do on the highway. it's all about gearing. the engine rpm's are from the speed, not load on the engine.

[blindman10]

Quote, originally posted by KITT222 »Air filter is good, I know that. We have yet to check the plugs, and the PCV valve, but I think it'd be worth it to give 'em a look. What is an IAT sensor?The IAT (Intake Air Temperature) sensor is located on the same part as the MAF. It can be cleaned in the same manner as the MAF. The IAT is the tear drop shaped one while the MAF sensor is more 'inside' the piece (if that makes sense).If you go to this thread the photos clearly show the relation of the IAT to the MAF. I highly doubt this sensor could be the sole culprit, but it may be a part of the puzzle.

[KITT222]

Quote, originally posted by bassplayaz06 »honestly, here's a suggestion... get a manual or a GT. they have better gas mileage. oh and my grand dad has a Pontiac G8 GT and averaged 28 mpg from the special fuel saving system where it shuts off 4 cylinders. it weighs more, and has a bigger engine and gets better mileage than i do on the highway. it's all about gearing. the engine rpm's are from the speed, not load on the engine.Well look at it this way: I got the best deal we could've gotten on a Vibe, and one has yet to match the deal we got. Lowest miles that I could find, lowest price I could find, and it just happened to be an automatic. And silver. And have a sunroof. And etc... There was a neptune 5-spd at a dealer near here in similar shape for similar price, but it was gone in a few days. If I wasn't so happy with my specific Vibe I would have tried to grab that 5-spd.

[yyamad1]

Yes I have a 5 speed and use a scan gauge to monitor my MPG, also use actual fill up gallons to calculate my MPG. like another person said even a .5 gallon difference due to top off, vehicle load ( stuff in the trunk), level ground, different pump nozzle can all affect the amount of gas you get to put in. So that is why I average out all the fill ups and I still get 30-32 in Chicago driving. Even with an AUTO i think your figures are little too low. Driving style does affect MPG alot.. I actually log better mileage in constant traffic where all the cars are moving 60-70, there is a strip stream effect from what I read, I dont tail gate but there is enough turbulence from other cars that improve mpg. Short shift and lugging the motor actually increase mpg, the motor is most efficient at WOT, I read that throttle body plate is part of the problem. because you have an AUTO I assume alot of my tactics can not be used. I read all of these tricks in Ecomodders.com my numbers are very poor compared to the people there, but seems on the good side in genvibe.com... I would also check intake manifold leak on your car, if you have oil dripping in the front of the motor, its an easy sign. I think the best part to replace first is the O2 sensor. They can easily affect 10%.

[yyamad1]

And any car can be modified to achieve excellent MPG. My brothers 91 Chevy Caprice with a crate motor gets 32 on highway! His car made the Ford employee news letter... yes he drives a Chevy.. lol The point is our cars should be getting 30s stock .... unless you drive it like its a sports car.... air temp and winter gas does affect it... One article I read said 1% for every 10deg so at 30deg temps.. you may get 5% less mpg just from denser air and wind drag. Ive learned alot from ecomodders web site, it all makes sense though.

[yyamad1]

sorry for the triple post, I forgot to mention, I did look into replacing my 5speed for a 6speed.. thinking more gears meant taller final gear. However that is not true, the 6 speed guys run about 200rpm higher even in 6th gear compared to 5th in the base models.. so The GT's stock will never achieve the MPG of base vibes. There were some talks about re-gearing these tranny to have a taller final drive but no one found a cheap way to do it. The easiest way for us is mounting taller tires.. however since I enjoy driving so much, I will keep my 215/50/17s RWD cars got it easy...