My 2003 mazda6 2.3 4-sp auto, 156k miles, has changed from 29 mpg to 24 mpg in the last 10K miles. I have replaced tires, oil change every 6-7k miles, new ngk iridium plugs/wires and ngk upper O2 sensor in the past 10K miles. Air filter and tranny fluid has 23k miles on it. What could cause such a drop? I drive 80% highway. The tire pressure is around 37 psi cold.
29 mpg to 24 mpg drop
- Thread starter usafstud
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Something broke or moved in the motor... Cam positions sensor, ignition timing system, something ...
I would check the EGR valve as well as the lower O2 sensor and the fuel injectors.
Summer gas bland.
I'm guessing bad fuel injectors. Using the best injector cleaner in a bottle won't guarantee they return to like new condition. There is someone here that cleans them I think.
Tyre pressure, driving habits, traffic, headwind or tailwind? Cargo or luggage? Fuel type/grade? Ambient temps?
Could be attributed to lots of things...
Could be attributed to lots of things...
try disconnecting the battery/resetting ECU maybe it is using the old profile since you changed all your parts
AZjeff
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Originally Posted By: Powerglide
Summer gas bland.
Thought winter blend lowers mileage. Can't be both.
Summer gas bland.
Thought winter blend lowers mileage. Can't be both.
One more thing to check.....Dragging brake. Run the car down the freeway, then pull off and check for a hot wheel. Using an infrared temp gun would make it easier.
I'm thinking injectors. A UOA might be helpful.
Also clogged cat or muffler. Or a bad battery causing an extra load on the alternator.
Could be 1000 things. Try all the cheap/easy stuff first.
Could be 1000 things. Try all the cheap/easy stuff first.
- new tyres have more thread and higher rolling resistance.
- did it get warmer so you're using the AC more intensely or driving with the windows down in stead of up?
- was the engine running lean on the old O2 sensor?
- gained some weight? check car and driver
- did it get warmer so you're using the AC more intensely or driving with the windows down in stead of up?
- was the engine running lean on the old O2 sensor?
- gained some weight? check car and driver
Originally Posted By: horse123
Originally Posted By: Powerglide
Summer gas bland.
Uh wrong... summer gas is more energy dense than winter. Try again.
Neither makes sense, if the loss has been over a 10k mile period. That probably is over a couple of seasons.
Originally Posted By: Powerglide
Summer gas bland.
Uh wrong... summer gas is more energy dense than winter. Try again.
Neither makes sense, if the loss has been over a 10k mile period. That probably is over a couple of seasons.
Usually this can be attributed to a stuck open thermostat in cold weather.
Provided location, time periods are not specific enough.
Provided location, time periods are not specific enough.
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gathermewool
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Originally Posted By: 4wheeldog
One more thing to check.....Dragging brake. Run the car down the freeway, then pull off and check for a hot wheel. Using an infrared temp gun would make it easier.
I would check this? When was the last time you serviced your brakes?
One more thing to check.....Dragging brake. Run the car down the freeway, then pull off and check for a hot wheel. Using an infrared temp gun would make it easier.
I would check this? When was the last time you serviced your brakes?
New tires are taller with more rolling resistance, that would account for some of the difference. Check inflation pressure, you may have had the old tires' pressure higher than the shop inflated tye new ones.
You may have had more wind in your face on this 10k run....I would see what the next one comes out to be.
You may have had more wind in your face on this 10k run....I would see what the next one comes out to be.
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