extremely low mileage per tank

[devillin]

I have a 2006 Mazda 3. I got about 300km per tank. It's very not normal. I have replaced new oxygen sensor, spark plugs, engine oil, and air filter. Engine light is not on. I really don't know what else to change. Everything drives normal but the gas mileage is really low. Can you all please give me some advise? Thanks a lot

[S.F.W.]

What type of driving ? City, traffic, ac on ? Highway ?

[silverstarmazda]

What type of driving ? City, traffic, ac on ? Highway ?

this plays a huge part.

also check your alignment, suspension parts, sticky brakes (ebrakes too), tire pressures and anything causing resistance. i can get approximately 450km or over on 1 full tank with careful driving.

[-ToM-]

AC plays a big factor, also your driving style and whether u drive city or highway. In city I get around 350-400, but on highway i get around 600-650

[_bradjames]

Just bought my '06 Mazda 3 GT. Got 400km's on my first full tank with a mix of city & highway driving. Was hoping for a bit more. Need to check tire pressure

[ryan2.3]

people need to ease up on that pedal. with a 50/50 split of highway and city, i can easily get 550 til the light goes on, and i do 120 on highways. Straight highway, like traveling to meet family, 600-700km /tank. Did a test with a jerry can and when the light came on, i was able to do about 150km extra on the light (there's about 10L left when it comes on) @110km/hr. 2004 2.3L hatch, empty car.

[JonsMazda]

07 GT, mix driving highway/city...getting around 450km. 500km pure highway.

Things you can do to improve fuel:
-take out junk you don't need in car.
-change air filter
-clean throttlebody
-put in fuel cleaning thing
-stop stomping on the pedal

[Nikhil Pali]

05 GT Hatch and I get 550-600 with 90% hwy driving and 525 with 50/50% driving until light comes on. I also found that switching to 0w20 increased my average from 11.2km/L to 12.4km/L and after fresh oil change gives my best mileage of 13.8km/L.

Also, where do you fill up. Try to fill up from some other gas station in other part of town. I once filled from pioneer gas station and got 400km per tank and car threw an engine light and once I filled for a gas station from first nation reserve and got over 620 km per tank (80% highway).

[Canadianbacon]

M3 2010 gt I get around 400km per tank. Mainly all city very short highway trips

[kimchisoup]

05 GT Hatch and I get 550-600 with 90% hwy driving and 525 with 50/50% driving until light comes on. I also found that switching to 0w20 increased my average from 11.2km/L to 12.4km/L and after fresh oil change gives my best mileage of 13.8km/L.

Also, where do you fill up. Try to fill up from some other gas station in other part of town. I once filled from pioneer gas station and got 400km per tank and car threw an engine light and once I filled for a gas station from first nation reserve and got over 620 km per tank (80% highway).

Fresh oil cannot improve mpg so drastically - its against laws of physics. Unless you had no oil before...

First, it seems 95%+ here and other forums have no clue how fuel gauge works - its a floater attached to variable resistor - its a rough estimate.
Until fuel goes below half of floater, gauge wont move from F. Once it reaches bottom (sooner if doing sharp turns or going over bumps), fuel level is at midsection of floater.
In my Mazda3, orange E shows up when trip computer says 30 km remaining - but 42-44L gets me to full. Since tank is 55L, that means 11-13L or about 22% is remaining.

The trip computer is off by up to 0.5L/100km.. and pumps at different stations are also off by few %, and temperature compensate.
Still, the best way to check fuel economy is to divide L pumped to full (2nd click) over km driven

Makes max 1-2% mpg difference (ie very little):
- hauling groceries, cargo, spare tire
- +/- 4 psi in tires. Only helps at slow city speeds, since highway is 85%+ air drag (and 15% rolling).
- types of oil, 0W20, synthetic etc..
- clogged/old air filter (only limits max hp at max rpm)

Surprisingly you get BETTER fuel economy at city speeds.. its obvious.. less drag.
Brisk acceleration from lights also makes LITTLE difference.. its slamming on brakes and throwing away all the kinetic energy that kills mpg.

What makes HUGE difference:
- temperature.. in winter takes ~7 min for engine/coolant to heat up - until then engine runs "rich" spraying fuel like a fountain to reduce emissions and prevent stalling.
- bad mass air flow or O2 sensor - since they are used to figure out how much fuel to inject
- wind. When its gusty 30 kph on highway, driving upwind maybe get 8L/100km, but downwind 6L/100km
- hills/lights. Remember, car burns little gas keeping speed steady.. kinetic energy stored.
Let's say one week you make most lights on way to work. Next week you keep hitting red at bottom of hill - that's HUGE difference.
- excessive idle. You're not going anywhere, but you're burning gas. Warming car in driveway for 10min is waste.. 2 hours stuck in traffic because of accident is even worse.

[loki]

This isnt another what fuel econony does your car get thread

he's asking about advice of what to check as he believes his car is suffering right now

So far there have been some good suggestions...

I would check your brakes. If you have seized or slightly seized calipers

All other references to other car's fuel economy will be deleted

[MazdaMike02]

Is it a manual or auto? If its an auto it may be a malfunctioning torque convertor, or an internal transaxle issue. Also I would check engine compression, fuel pressure, verify closed loop fuel control. The problem with a fuel economy issue is it could be many different things. Good luck, hopefully its not an engine or trans issue.

[narindra]

meh no idea. i average about 400km a tank on a 2013 GS/Sky but i drive like a maniac and mostly city driving(90% city). To be expected really in Toronto. However when i do highway driving, i do use cruise control as much as possible i can pull anywhere from 700-800 a tank. I like to keep my trunk as empty as possible, if anything happens mazda road side assistance lmao. Passengers also account for the weight, if your using it as a family car might also explain a few things. Fuel injectors may be dirty, tire alignment etc, only person that can really answer this is your self, whens the last time wheels were aligned if ever? whens the last time you cleaned your fuel injectors, what are the actual condition of your tires how much stuff is in your trunk ? how many passengers do you have in your car, are yo one of those guys that likes to go through drive throughs and or idles your car like its nobodies buissness. Answer should come to you after you think about these things.


hope some of this helps.

[Cab0oze]

Fresh oil cannot improve mpg so drastically - its against laws of physics. Unless you had no oil before...

First, it seems 95%+ here and other forums have no clue how fuel gauge works - its a floater attached to variable resistor - its a rough estimate.
Until fuel goes below half of floater, gauge wont move from F. Once it reaches bottom (sooner if doing sharp turns or going over bumps), fuel level is at midsection of floater.
In my Mazda3, orange E shows up when trip computer says 30 km remaining - but 42-44L gets me to full. Since tank is 55L, that means 11-13L or about 22% is remaining.

The trip computer is off by up to 0.5L/100km.. and pumps at different stations are also off by few %, and temperature compensate.
Still, the best way to check fuel economy is to divide L pumped to full (2nd click) over km driven

Makes max 1-2% mpg difference (ie very little):
- hauling groceries, cargo, spare tire
- +/- 4 psi in tires. Only helps at slow city speeds, since highway is 85%+ air drag (and 15% rolling).
- types of oil, 0W20, synthetic etc..
- clogged/old air filter (only limits max hp at max rpm)

Surprisingly you get BETTER fuel economy at city speeds.. its obvious.. less drag.
Brisk acceleration from lights also makes LITTLE difference.. its slamming on brakes and throwing away all the kinetic energy that kills mpg.

What makes HUGE difference:
- temperature.. in winter takes ~7 min for engine/coolant to heat up - until then engine runs "rich" spraying fuel like a fountain to reduce emissions and prevent stalling.
- bad mass air flow or O2 sensor - since they are used to figure out how much fuel to inject
- wind. When its gusty 30 kph on highway, driving upwind maybe get 8L/100km, but downwind 6L/100km
- hills/lights. Remember, car burns little gas keeping speed steady.. kinetic energy stored.
Let's say one week you make most lights on way to work. Next week you keep hitting red at bottom of hill - that's HUGE difference.
- excessive idle. You're not going anywhere, but you're burning gas. Warming car in driveway for 10min is waste.. 2 hours stuck in traffic because of accident is even worse.
Good advice for everyone there. I like your posts lol


This isnt another what fuel econony does your car get thread

he's asking about advice of what to check as he believes his car is suffering right now

So far there have been some good suggestions...

I would check your brakes. If you have seized or slightly seized calipers

All other references to other car's fuel economy will be deleted OP is hit and run and this thread is from June. You all need to learn to read the thread before instantly replying with you opinions/ideas lol

[kimchisoup]

meh no idea. i average about 400km a tank on a 2013 GS/Sky but i drive like a maniac and mostly city driving(90% city). To be expected really in Toronto. However when i do highway driving, i do use cruise control as much as possible i can pull anywhere from 700-800 a tank. I like to keep my trunk as empty as possible, if anything happens mazda road side assistance lmao. Passengers also account for the weight, if your using it as a family car might also explain a few things. Fuel injectors may be dirty, tire alignment etc, only person that can really answer this is your self, whens the last time wheels were aligned if ever? whens the last time you cleaned your fuel injectors, what are the actual condition of your tires how much stuff is in your trunk ? how many passengers do you have in your car, are yo one of those guys that likes to go through drive throughs and or idles your car like its nobodies buissness. Answer should come to you after you think about these things.


hope some of this helps.


If you suspect there is something wrong causing poor mpg
Here is "the test"

On a dry warm (>15C) day with relatively little wind (<20kph), and little traffic on 401 (perhaps night)
1. Drive minimum 10 min to warm up car.
1. Fill up near an exit to the brim (ie see gas spilling). Keep going VERY SLOWLY after click and checking FREQUENTLY.
2. Drive minimum 100 km down 401 with cruise control ALWAYS on (ie 100 or 105 kph.. exact speed doesn't matter) and NO AC/heating of any kind. This is to remove / average out errors.
3. At your destination very near highway exit, once again carefully fill up to brim. L tanked / km driven = L/100km.
4. Now do the return trip. Once again cruise control. You should be almost never changing lanes/passing anybody.
5. Now fill up where you started near highway again to the brim.

you should get within 5% of EPA highway (or better!)- check fueleconomy.gov for your car's rating.
A perfect place to do this is Oshawa to Cobourg at night.

This test eliminates most of the major sources of error:
- typically before engine reaches operating temp, it runs open loop "rich"
- gas pump click is not reliable indicator of fuel level.
- 10% denser air for every 20C change.
- steady speed on highway is a controlled environment - most people underestimate how much they pass others.
- 401 is very flat, but return trip accounts for wind and hills.
- ethanol has minor effect, but you could fill up Shell 91 for this test.
- tire size has minor effect, but you could use GPS instead of odometer.

95% of friends/family complaining about fuel economy... stopped after this test.
Even a compact loaded with school supplies and an underinflated leaking tire managed within 5% of EPA highway rating (over 33mpg fyi)

Only come back to forums complaining about mpg/fuel-economy AFTER DOING THIS TEST with the results.

[kimchisoup]

The cost of this 200km "test" is about $15-20 and 2 hrs of your time.
1 hr at mechanic is $90.. so well worth it.

Gas pumps aren't super accurate, so doing fill up each way allows you avg out their error.
Depending on how careful you are, how level the car is and how well gas settles, you should be +/- 0.1L

I did Cambridge to London around 90 km at 6.4L/100km east and 6.9L/100km west in 2.3L 2008 Mazda3.
Friend's Protege, Cruze and SunFire also did better than 8L/100km although they did smaller less accurate 50km "loop" (take exit and return) back to same gas station.