fuel consumption

[joecass]

I change the oil on my 2012 mazda5 and noticed that im getting 80mils less a tank than before. it's a 6 speed manual trans. I was getting 32mpg now im getting 23mpg. has anyone have this problem? no check engine light

 

[thaxman]

Still using 5W20? Also, WHEN did you notice the decrease in mpg? Around the time it got hot & muggy? The AC robs at least 20% of the engine power on the 2.3, probably nearly as much on the 2.5. I go from 24 city w/o AC to 17 city in the summer.

 

[rodslinger]

I change the oil on my 2013 mazda5 and noticed that im getting 80mils less a tank than before. it's a 6 speed manual trans. I was getting 32mpg now im getting 23mpg. has anyone have this problem? no check engine light

I had the problem in which I've never in my life squeezed 32mpg out of any 5 I've owned regardless of how I drove.

Might recheck those calculations or driving method. I only expect you would get 32mpg if you got on the interstate, held 60-65mph for the entire tank and stopped only to refuel. You'll never see that in daily stop and go driving. I'm guessing, especially in Jersey, that your 23 is closer to reality.

 

[Secondtyme]

How are you computing that mileage? If you are relying on the cars mileage computer with no source of corraboration DON"T. At 32MPG you would be getting approximately 515 miles out of 15.9 gallons of fuel. That is waaaaaayyyy better than most anyone on here has ever gotten. My experience has thus far been 28MPG with the AC off and 26MPG with it on. Mine is an 06 with the 2.3L engine and 4 speed auto.

 

[eyeballs]

I managed 34mpg once in my wife's 5. 65 mph all highway, net loss of elevation (north GA to FL). Tires pumped up to about 40 psi, took off the roof rack. I also managed 43 mpg once in my 2. Its not typically how I drive, but when I'm in a good mood, in no rush whatsoever, and want to challenge myself on public roads it helps keep me occupied.

 

[Robotazky]

Your calculated mpg will be all over the place like no other vehicle. Don't worry about it.

 

[joecass]

i had mazda run faults and they found a fault for mass air flow sensor. but because there were low voltage faults also stored they only cleared the fault. i used to get close to 400 miles on a full tank. now im down to 330 miles. i would be able to go back and forth two work all week on 1 tank now i have to fill up 2 times. see what happens after they cleared the fault. i have a lot of stuff pluged into cig. light they said to keep everything unplugged from the cig lighter for now.

 

[thaxman]

i had mazda run faults and they found a fault for mass air flow sensor. but because there were low voltage faults also stored they only cleared the fault. i used to get close to 400 miles on a full tank. now im down to 330 miles. i would be able to go back and forth two work all week on 1 tank now i have to fill up 2 times. see what happens after they cleared the fault. i have a lot of stuff pluged into cig. light they said to keep everything unplugged from the cig lighter for now.

This brings up a side topic...

<<HIJACK ALERT>>

Has anyone else noticed if their low fuel light comes on earlier and earlier? I've gone from light on around 13 gal to less than 12 gal. used or more than 4 gal left in tank. This week drove a good 30 miles w/light on and when I filled it, only put in 13.3 gal. Weird... :dodgy:

 

[Secondtyme]

The only way to know for an absolute certainty is to fill up at not only the same station, but the same pump as when you last filled your tank. Also, do you top off or just let the auto shut off do its thing? My SGII shows fuel light on at 3 gallons to go consistently, sometimes she drifts to 3.5 gallons to go but seldom below 3. I drive my wife nuts because I routinely go 70 some-odd miles with the fuel light on. I should qualify that statement by saying that I religously updateand use my economy tracking on the SGII, that thing is a godsend when you drive as much as I do. Joecass, a higher electrical load shouldn't affect your fuel economy, unless Mazda has fitted the 2013 models with a clutched alternator (stranger things have happened) A faulty MAF might do it though, depending on how it failed it could cause the engine to run rich. Get yourself a Scangauge, or Ultragauge, either will allow you to observe things like MAF readings and Air Fuel Ratio on the fly, greatly increasing your ability to communicate with the service guys at the dealer.

 

[MarkVII88]

That sounds about right to me. I routinely drive 1/3 highway and 2/3 city, getting about 300 miles before the gas light comes on. I usually wait till the gas light comes on before filling-up too. When I fill it up, the average amount it takes is about 13 gal. I've never tried to push it and see how far I can drive with the gas light on, even knowing that I've got a good 2 gallons of gas remaining.

 

[Secondtyme]

I make a game out of it, look the Scangauge says I've got 2/10ths of a gallon left, we'll just see about that! LOL It just so happens that I am able to fill up at the same gas station virtually every time I fill up, and with the SG being constantly updated it really is THAT accurate. To date I haven't stranded myself yet (I say that because it really, really isn't the cars fault)

 

[eyeballs]

I've got the ultraguage...but having all that info makes driving even more fun. I can definately keep myself busy watching things on highway trips to prevent boredom.

 

[joecass]

the mass air flow sensor did not fix it. really disappointed. that was $250.00

 

[rodslinger]

the mass air flow sensor did not fix it. really disappointed. that was $250.00

I still contend that your 23mpg is closer to normal especially in city style traffic. Was that 32mpg a one time calculation? Going by the trip computer (not that accurate) or was this a long term average using real math? Miles divided by actual gallons used.

Try and use fuelly.com to keep track of your economy. Just enter your mileage and gallons used at every fillup to see your trends. Input notes based on driving style for the previous fillup to see how and where you drive affects mileage.

There are only four people tracking mileage for the 2013 but quite a few for the 2012 model. No difference but the overall average seems to be about 24mpg.
http://www.fuelly.com/car/mazda/5/2012

Regarding the MAF sensor faults for low voltage if anything that particular fault may have lended to slightly better fuel mileage. Sensor output voltage is directly proportional to airspeed across the sensor. The ECU uses this value (along with other inputs) to help determine fuel demand with short term corrections done via air fuel sensor feedback. If for some reason the sensor was reading low the ECU would be trying to lean the mixture with the air fuel sensor bringing the ratio back in check. There are certain open loop scenarios that the air fuel sensor isn't correcting for in which any low voltage signal from the MAF (within reason) wouldn't get corrected for.

 

[Secondtyme]

Why in the world would you spend your own money on a MAF sensor that the dealer told you was bad? On a 2013 MY car that should be a goodwill repair 19 times out of 20. And for the record how close to 400 miles were you going on a tank? And how many gallons did it take you to fill back up? My Scangauge will register 999 miles per gallon while I'm coasting downhill, that doesn't mean i expect to go 15,000 miles on a tank....

 

[joecass]

I take the same ride to work everyday. I used to be able to go back and forth to work and do some driving on sat. on one tank. now I have to fill up around thersday. If I let the gaslight come on I would be around 400 mils now im around 340 mils. last time I filled up it took 13.5 gallons. I drove about 310mils. sorry guys it's a 1012 with 41,000 mils no more warranty also it's a 6 speed manuel trans. im getting 22mpg driving the car very very lightly. if I drove it normal I would be probably around 14 mpg.

 

[rodslinger]

So you have approximately 35 mile commute to work. What portion of that is absolute steady state 60-65mph cruising. That will pretty much be the only time you'll ever see 32mpg. You need absolute numbers to know your mileage and average it for several tanks. Keep real track. As in you drove 347.3 miles and used 12.43 gallons. That's 27.94 mpg.

What other uncontrollable factors are also involved. For instance;

The last three fill-ups I thought my 2011 Dodge Dakota with the 4.7 V8 was getting about 26mpg. I know that isn't possible but the miles I drove divided into the gallons I just put in it is telling me otherwise. I'm about to call Dodge about this miracle truck when I find out that my father-in-law used my truck a few times while I was out of town. In doing so he would put back in a few dollars in gas. Not enough for me to really notice on the gas gauge but enough to throw off my mileage. Hopes = crushed.....

Now I doubt some good Samaritan is tossing gas in your tank at night but something changed. Time of day you drive, route, weather, etc... If you were driving at night working 3rd shift with no traffic and you went to 1st shift and are now stuck in the grind with the rest of us then I would imagine your mileage suffered.

 

[thaxman]

I think that kind of drop can be attributed to a combo of A/C use and your local stations switching to summer gas. Adding ethanol or methonal or MTBE or whatever your local muni calls for is usually good for a 10% drop. Add 15-20% for power-robbing A/C use and there is your loss.

 

[Secondtyme]

I have re-read my responses in this thread and realized that I sound like a complete a$$hole. For that, joecass I apologize. I somehow thought you were driving a brand new 2013 5, not a 2012 with 41K on the clock. Now, back to the matter at hand. I second what others have said about carefully tracking your mileage to establish what has changed. If at all possible, fill up at the same station two or three times in a row. Try to eliminate any odd, pattern wrecking trips also. You sound like me in that you have a set weekly routine for commuting. I also forgot that NJ doesn't allow you to pump your own gas, so you are at the mercy of the person doing the pumping, where I can control whether or not I top off (I always do, religously) Now that I think of it, that may be a LARGE part of what is going on. If the vapor recovery apparatus on the pump isn't working right and the pump auto stops early, and the pump jockey doesn't top off, you could be getting "short filled" Where you are taking on less gas with each fill, does that make any sense?