Mazda 5 GT Poor Fuel Economy Help!

[BallLightning]

Hello all,

I don't know where else to turn to for advice so I'll be asking on this forum. Please give me any insight into how I can fix my car.

I bought this car new last year in July and have noticed that my fuel economy is horrible. I get less than 200 miles per tank (15.9 gal) when my inline 6 IS300 can go at least 300 (17.5 gal). These numbers are on both city/hwy usage.

I purchased the car at Putnam Mazda in Burlingame, CA and it's also where I get my car serviced. I took it in and asked them to check the fuel system and they said it was fine. I showed them my fuel consumption logs and they just shrugged me off and said that's just how it is.

I store nothing in the car. I use regular gas. The oil's been changed, the tires are at optimal pressure, fuel system checks out...what could it be? I drive my IS300 much more aggressively than the Mazda 5 which I sort of pamper.

Please help me what should I do? I am spending more money on gas than I should be. I bought the car for its decent gas mileage but now it's turned into a headache.

Thank You in Advance!!!!

 

[Mazda5wannabe]

Wow, that is atrocious mileage for the 5. I can get 24 mpg (US) easy, and I'm a bit of a hot-footer.

Are you spending lots of time trapped in the parking lots that California laughingly calls freeways? That will slaughter your mileage.

 

[kleptomaniak]

That is odd and seems uncommon. The MZR has a long stroke, so I can see how you will burn more gas than it's worth if you step on it all the time. If you drive economically, it will return 25+ consistently.

I drive an 06 GT 4SP auto. The model that could possibly return the worse MPG out of all the US 5s created.

I just came back from vacation from SF, CA to San Diego, CA to Palm Springs, CA. I logged about 1300 miles. I gassed up 4.5 times. That equates to about 19 MPG.

I'm running aftermarket rims and wider tires, so my unsprung weight is not ideal. I also had a fully loaded Yakima cargo box (rocketbox 15s), two kids, and my sidekick. You can say I was fully loaded, so the 19 MPG was reasonable. I was also flooring it on the grapevine, and averaging about 75 on Hwy 5.

 

[BallLightning]

Thanks for the replies guys! I don't lead foot in the Mazda, bc it's not all that fast anyway so it puts my driving mentality into "snail" mode. I drive 70ish on the freeway with mostly no traffic combined with normal city driving. Should I try resetting the ecu by unhooking the battery?

 

[njaremka]

make sure you are calculating your mpg correctly. while it may seem trivial, there is a right way to do it.

start with a full tank, and zero out the trip computer. drive as you would, and run the tank down alomost empty. (at least down past 1/4 mark on the gauge) fill the tank, and note the mile on the trip computer and the gallons pumped at the pump display. divide the miles from the trip computer with the gallons noted from the pump, and this is your proper mpg usage.

to get an even better note as to your fuel consumption, average this out over about a months worth of time and miles.

that being said, 200 miles on a tank is not that good. but note, a LOT of stop-n-go driving will negatively hurt your fuel consumption. we average about 300 miles of around town driving in our 5. and while that isnt as good as my protege, its not really that bad and is well within the ratings from the EPA.

 

[twintrbo]

I have my 09 touring about 2 months now, and about 1300 mi on it. The mileage has yet to be over 20 MPG no matter what. Its almost like the car will aim for 260 mi per tank and just dump fuel when it gets there. I live in Brooklyn, NY and most of my driving is city combined with mostly stop and go highway driving, usually a light load of me, wifey, 3 yo and the 5 month old. I'm not a speed demon either and I try to be as smooth as possible from my educations in race driving. But even when I take a trip somewhere and get great mileage there and back, it somehow sucks down the last half of a tank to average the same 20, if I didn't know better I would think someone is taking gas out at night to mess with me. Its rated 22 city, so it not that far off for a tight new engine but I was def expecting more of this vehicle.

I do have 2 theories though:
1. The low first gear of the auto wastes fuel by spinning the motor so fast off the line.
2. It upshifts early and lugging it wastes more fuel then spinning it, most NA engines are most efficient at full throttle after all.

 

[diogenes]

Our 2006 Mz5 gets driven in the worst-possible way for fuel mileage -- almost all short trips in the city. We sometimes go through a whole tank rarely getting out of third gear. The results: about 18 mpg. When we do get out on the highway for once, mileage soars to as high as 30 mpg.
Some possible problems and answers:
Dirty air filter -- replace
Driving too much "on the cam" (the variable valve timing shifts at about 3300 rpm) -- stay below 3300 when you can
Dirty mass airflow (MAF) sensor -- use a can of MAF cleaner
Dirty fuel injectors -- use a bottle of Techron in the tank
It sounds like you've addressed the other issue -- tire pressure -- so your idea of clearing the computer might be a good one.

 

[SGT_OKINAWA]

(hah) Take all the crap out of the back cargo area and get on a diet!

J/k (beer)

For real, what everyone here has said and consider wight a factor, if you DON'T use the back seats (Little ones all the way back there) take them out of the car, they weigh a ton, get a floor mat back there and some carpet and you are good to go !

Good luck!(rei)

 

[5zoom]

I get 24-32mpg on average out of my 08 5AT. That is based on about 30% city/70% highway. MPG drops off significantly beyond 75mph.

I recommend getting a Scangauge http://www.scangauge.com/. It takes a few tanks to calibrate it and get all the settings right, but its definitely worth it. Small adjustments with the throttle can yield big MPG increases if you pay attention to it.

 

[thaxman]

OP, we need your year/tranny to get a real idea of what's going on. the 4-speed auto will return the worst city mileage, while the 5-speed manual will suck the tank dry at real Western States freeway speeds, as you could very well be cruising @ 4000 rpm. Also, not sure which CA Burlingame is in, but if you have been using your defroster over winter, your A/C has been on, so that's 1-2 mpg right off the top. We have been getting 19-20 ALL city in summer and 23-24 over the winter, but we have dry desert winters, so no defroster necc. Also, the car does warm up really quickly, but if you drive <4 mi 1 way, then shut it off long enough for it to cool down before starting up again, you can take 1-2 mpg off as well, as all cars guzzle fuel when cold. Is your driving route/distance different than in the IS? Also, remember that your IS has an I6, so it has more torque, hence a better final drive ratio. At real highway speeds, a low-torque 4-banger will use as much gas as a 6-cyl because the manufacturer will mate taller gears to the smaller engine to take advantage of its max hp, which is high in the rpm range, which eats more gas. My bro-in-law had a '99 V6 Accord and I had a '97 VTEC 4-cyl. On a trip back from an out of town family meet, we caravaned @ 80 mph, both getting 26 mpg. the 4-cyl was running @3600 rpm, and I think the V6 was near 3000 rpm.

 

[BallLightning]

Wow I didn't expect this amount of help and feedback. Thank you all again for taking your time to help. (bowdown)(bowdown)

I drive an 09 auto with about 5000 miles on it.

njaremka: The way I check my mpg is exactly as you describe it. I take note of the miles driven exactly when the low fuel indicator comes on.

I drive the same mix of city/fwy on both cars that I own. I never use the A/C in either car.

diogenes: I'll be looking into the solutions you mentioned.

5zoom: thats 170$ i dont have lol

thaxman: interesting info. thanks!

 

[njaremka]

njaremka: The way I check my mpg is exactly as you describe it. I take note of the miles driven exactly when the low fuel indicator comes on.

thats fine, just dont divide that number by the rated capacity of the fuel tank. when the light comes on, you still have AT LEAST 2-3 gallons left in there.

 

[AO928]

After driving the car for a bit, check to see if any of the wheels are hot. If they are, this would indicate a draging caliper or stuck parking brake which would reduce gas mileage.

 

[Heat]

...njaremka: The way I check my mpg is exactly as you describe it. I take note of the miles driven exactly when the low fuel indicator comes on...

It's fine to fill up when the light comes on, but divide the number of miles by the number of gallons you actually put into the tank at the gas station, not 15.9 gallons which is the tank capacity.

 

[mpvue]

I see this on all kind of car forums; someone is getting bad mpgs and they automatically assume it's a problem w/ the car, even brand new ones.
but it never is.
problem is always the driver.
seriously, no one ever thinks they have bad driving habits or do wasteful things, but we all do (ever drive w/ a friend and you notice they keep the clutch depressed the whole time they are stopped at a light?)

1st of all, make sure you are figuring out your mpgs correctly. most people don't.
2nd, honestly evaluate your driving patterns.

for comparison, I drive an '09 5 speed M5, mix of hwy and local maybe 70/30, A/C used lately, 75-80mph hwy. my last tank was almost 24mpg. when we did a hwy trip a few months back, best tank IIRC was 29.
btw, I usually fill up about 240-260 on a tank, that shows about 1/4 left.

 

[BallLightning]

It's fine to fill up when the light comes on, but divide the number of miles by the number of gallons you actually put into the tank at the gas station, not 15.9 gallons which is the tank capacity.

Right that's what I meant sorry. I thought it was simple logic so I left that part out . In my OP I put down the tank capacities for you guys to reference, I never divide by those numbers.

mpvue: I'm figuring out the mpgs correctly; I've kept a log for months. I am very honest about my driving patterns. I've changed my habits in the M5 by consciously "feathering" the gas from dead stops and coasting to red lights etc. What irks me is that I get more MPG in my IS300 which I much much more aggressively.

Thanks again for everyones input, I wouldn't have come on here hollering for help if it were something I could do on my own like monitoring my own driving habits for gas guzzling tendencies. You would have to drive incredibly reckless to get 200 miles per tank (roughly 13 mpg).

 

[Heat]

Have you spoken with Mazda?

I used to hang out occasionally at a Honda Odyssey forum, Odyssey's normally get 17 to 18 mpg if I remember right. There was one guy whose Odyssey was getting around 10 to 11 mpg and he was very careful about what he did, he spoke with Honda and was told that it was within spec or something like that. But talk with Mazda, see what they say.

I drive an '09 5 speed M5, mix of hwy and local maybe 70/30, A/C used lately, 75-80mph hwy. my last tank was almost 24mpg. when we did a hwy trip a few months back, best tank IIRC was 29.

That's right at what I get with my '09 5 speed m5, similar driving conditions.

 

[KBrian]

At the risk of pointing fingers already aimed in your direction, BallLightning, 15.9 x 13 mpg is pretty close to 200. If you fill up when the yellow light comes on, only 12 -13 gallons should be used. That would be more like 18 mpg. Admittedly still crappy, but much different than 13mpg.

Personally, I too keep a log and rarely get more than 500km (310miles) for 50L (13 gal) and often am closer to 450 km if aroung town driving.

I have an 07 GT 5spd with 30000km (19000miles) and I keep the tires at 36lbs. Mostly driven empty, no roof racks or hitches. I often short-shift from 1st to 3rd, but also run it up to redline when no-one's looking.

BTW, the best highway tank ever was about 680 km for 56 L.

I too was frustrated because I retired a V6 sedan that got better highway mileage and the same around town. I balance the thrills I get from the 5 against disappointing economy and feel like a winner.

Finally, I apologise for sounding like a hater, because i'm not. I just try to understand what I read and share my opinion.

 

[AIMWO4]

I can't really say what might be the cause of such terrible mileage. I get about 25 MPG in mine and drive like a nutcase. I only fill up about every 2 weeks due to my short commute. I should think my mileage would be better if I had longer trips.

Other than dirty air filter, clogged cat. or a bad ECU, it's a bit baffling.

 

[AO928]

One other possibility is that the gas station is ripping you off - Charging you for 15 gallons but only delivering 12 or 13. Just sayin. You may want to try a different gas station to be sure. It wouldn't be the first time.