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Hello! I have installed the trany cooler as described on this forum 3 months ago. My m6i (4c) was doing about 26-28 mpg average. For the last month or so I have had to refuel much more often so I just check on average over a week of driving how does it do. I am very worried, 18MPG!!!! I don't know what the heck is wrong. I don't blame the cooler but I want your input. I am thinking to take the cooler off and take the car to the dealer.
What do you think might be wrong? Should I take the cooler off or take it like this? I am thinking to changing the spark plugs too Monday.

Few details: I live in Seattle, just passed 30k miles, synthetic blend oil in the engine, my model is the firs one 2003 mazda 6i. No problems the car runs smoothly (ok it does the kick you in the nuts ... sorry rear :) from shifting 1st to 2nd).
 

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I'm suspecting the following:
1. Oil change with heavy weight oil
2. Winter gasoline reducing mpg
3. low tire pressure
4. air filter dirty

I don't think the ATF cooler got anything to do with it.
 

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I'm suspecting the following:
1. Oil change with heavy weight oil
2. Winter gasoline reducing mpg
3. low tire pressure
4. air filter dirty

I don't think the ATF cooler got anything to do with it.
[/b]
Christ, I hope not, mine comes in the mail tomorrow :laugh: ...but seriously, I doubt the cooler would have anything to do with that...in fact, would anybody agree that it might reduce consumption a little bit cause it increases efficiency...no?...just a thought.
 

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It is highly unlikely that an ATF cooler would drop MPG. But, if that is something you worry about, then install a thermostat on that cooler. Some vehicles, that monitor ATF temp, have delayed upshifts and delayed TC lockups to warm up the transmission quickly. I haven't noticed that in my 6i.

Sounds like you need a good ol' fashioned tuneup.

New Mazda air filter is a must. I change my air filter yearly. We use lots of sand on the roads during the winter. I would never consider running it longer then 1 year.

Oil/oil filter. Make sure you are using a blend or full synthetic 20wt. 0w will provide slightly better cold efficiency then 5w in those northern winter climates. IMO, synthetics are best. Consider a 5-10 minute solvent flush at your next few oil changes. Carbon, crud, or sludge buildup could cause MPG/HP issues.

ATF, get it flushed if you haven't. Then practice a simple drain/refill every 6-9 months with a good blend MerconV or Multivehicle ATF. Use a synth like Redline, Mobil1, or Amsoil, if in your budget.

My plugs look excellent at 35k miles. They should easily last 100k. When in doubt, replace them. I'll just clean, gap, and dielectric grease 'em.

Alignment; I find many cars that lose MPG because of bad alignment. Even if you car tracks straight doesn't mean that it is correct. Equal uneven tire wear is something to look out for. Tire pressure is just as important. I check my WEEKLY using a quality calibrated tire pressure gauge. No pencil or stick tire pressure gauge here! And, I like to run 2+ PSI over the OEM recommendation.

PSF, don't forget to siphon/refill your PSF. Use the same fluid as your AT.

FI and IVD cleaner: You should consider running 2-4 bottles every year of quality fuel system cleaners. Some of the good ones are BG44k, Ventilsauber, Techron, Regane, Redline, Amsoil......... These will remove any valve deposits, help keep the injectors clean with good spray pattern, and help remove carbon deposits in the combustion area(your pistons and chamber).

Inspect the brakes. Something like a dragging caliper, hung E-brake, could cause a drop in MPG. You should be bleeding your brakes every 2 years which will let you inspect everything, if your brakes even last 2 years.

If road salt is used in your area, you should clean all power and ground cables. Corrosion will affect performance. Brush clean all drivetrain ground, battery, starter, alternator,....cables.

While at the dealer, make sure you have the lastest ECU software update, and that all sensors are working.

And, how did you plumb your ATF? alone, parallel, or series with the stock cooler? before or after?
 

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I'm suspecting the following:
1. Oil change with heavy weight oil
2. Winter gasoline reducing mpg
3. low tire pressure
4. air filter dirty

I don't think the ATF cooler got anything to do with it.
[/b]
+1 for #2 on the list. Winter gasoline (Ethanol blends of 10 -15%) are just about everywhere. In fact, most states sell these blends year round. Ethanol is a grain alcohol that hepls gas burn cleaner. The downside is increased consumption. Actually, the bigger problem (at least for me in Philly) is KNOWING when you are actutally using it. Most stations do not identify the fuel by blend E10- E15. Some post a VERY small disclaimer that the fuel COULD contain ethanol. So there you go...one tank great mileage...next tank lousy mileage :yesnod:
 
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