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Discussion Starter · #1 ·
i've got an 06 that i've owned since it had 3k on it. i have averaged anywhere from a low 18mpg(city driving) to a high of 23.5mpg(highway). i just went over the 70K mark and out of the blue, i cant manage anything better than 15.5 highway. i"ve cleaned the air filter and reset the ecu and nothing has changed. what i have noticed is the load percentage for the TPS is reading around 23%-24% at idle! that seems extremely high for idle. i thought that it should be reading 3%-5% at idle. can anybody measure thier load percentage for me so i have something to compare it to? HELP! i've gone from 320miles per tank of fuel to 200! this is killing my wallet!
 

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I had the plugs and ALL fluids changed at 60k, and I have not noticed one bit of difference in MPG. Fuel filter? Tire pressure? Gas cap on tight (this will usually trigger the check engine lights)?

-Karen in AZ-
 

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Discussion Starter · #3 ·
the dealer i have to deal with is horrible. they never once mentioned that the plugs and so forth needed to be changed at 60K. i've been doing a little research and fuel filter, plugs are on the list. never had a check engine light. and i have brand new tires and the pressure has been perfect.
 

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ej25turbo said:
i've got an 06 that i've owned since it had 3k on it. i have averaged anywhere from a low 18mpg(city driving) to a high of 23.5mpg(highway). i just went over the 70K mark and out of the blue, i cant manage anything better than 15.5 highway. i"ve cleaned the air filter and reset the ecu and nothing has changed. what i have noticed is the load percentage for the TPS is reading around 23%-24% at idle! that seems extremely high for idle. i thought that it should be reading 3%-5% at idle. can anybody measure thier load percentage for me so i have something to compare it to? HELP! i've gone from 320miles per tank of fuel to 200! this is killing my wallet!
I have almost the same problem, though I have no idea how to "reset the ECU" or "measure load percentage" :eek: Could you tell me what to do? I'd be glad to help finding the reason :)
 

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Discussion Starter · #5 ·
reseting the ecu was just disconnecting the battery for around 15 minutes. i got the load percentage from a cheap OBDII code reader that plugs into the diagnostic port under the steering column. its come back up a little but so has the overall temperature outside. it seems like the colder it is, the worse the gas mileage. btw, i bought the code reader at a local Harbor Frieght tool for around $40. it reads check engine lights plus 3 different live parameters, coolant temp, RPM, engine load percentage.
 

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Discussion Starter · #7 ·
what i have noticed is that the colder the outside temp is, the worse the MPG's are. on a 45 degree day my gas mileage is normal. on a day that it drops to 10 degrees, i get around 14mpg. it doesnt make any sence. the colder (more dense) air should make it easier to produce the power that the car needs to move. i'm guessing at this point its ecu programming related so it out of my control. anybody else notice this?
 

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You may be experiencing lower MPG's if you're running the car @ idle to warm it up....
 

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The guys on Car Talk/NPR discussed mileage loss in cold weather this morning. You will lose some mileage due to colder outside temps. no matter what, but you should check your tire pressure and if you're losing a lot of mileage you should also check your thermostat.

Seems like this issue comes up from time-to-time -- here is the same discussion in 1997:

http://www.cartalk.com/content/columns/Archive/1997/March/01.html
 

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I have this issue also. 2 weeks ago I had the 30K service done and now my highway mileage is worse than it used to be. I visit my dad (about 4 hours away) a few times a year and I always average 22-23 mpg. Last weekend I averaged 20 and I'm quite annoyed...
 

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Discussion Starter · #12 ·
well, ive tried to keep an eye on the mpg lately, and ive come to a conclusion. the transmission in the tribeca is a "lock up" tranny. which means at highway cruising speed the torque converter "locks up", so it turns at a 1 to 1 ratio with the engine. my high way mileage is not the issue, its still around 22-23mpg. now, im guessing that the transmission fluid has been broken down over time and use. im assuming that it will eventually lose its viscosity, therefore, not transfering the engine power through the torque converter as effectivly. so around town in stop and go driving my fuel economy sucks because the drivtrain isnt being as efficient when torque converter is not "locked up". does this make sense to anybody else, or do i just sound full of ****? im gonna change the tranny fluid and try and see if i notice a difference. has anybody seen and increase in MPGs after a tranny fluid change?
 

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Yep, I definitely see an mpg boost after a tranny drain and fill. It's recommended every 30,000 miles, I believe. Subaru recommends against a power-flush - it could damage torque converter vanes.

Torque converter lock-up and transmission slippage are different things. Your torque converter still locks up fine, but transmission may be slipping if your fluid is broken down.

The torque converter can have a 1:1 ratio, when in lock-up, but your transmission ratio will only be 1:1 with the engine if you have a 1:1 gear (which, in Subaru's 5EAT happens to be 4th gear - 5th is 0.834:1 (output shaft rotates once for every 0.834 rotations of the input shaft - greater than 1:1)).
 
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