Had a local shop install the Subaru transmission cooler in 08 Tribeca (41k miles) and they also changed the oil.

 

Prior to the transmission cooler installation I was getting 19-20 mpg, since the install (3 fill ups), I've gotten 16-17 mpg. This is real-world fuel economy, I always divide miles by gallons at every fill up.

 

Same shop changed the oil the last time. This is the 2nd oil change I've had down since owning the vehicle.

 

Has anyone seen this before?

 

Thanks

I don't think installing a transmission cooler would affect fuel millage. My guess is that it is a small radiator installed in front of or behind your regular radiator. It would not be powered by the engine, and added weight to the vehicle would be very negligible.

 

Your lower gas millage is due to something else. Maybe you need a tune up, check tire inflation for proper pressure, or PCV valve to increase gas millage. Do you have a check engine light on?

should not be cooler related.

 

wait and see over a few tanks, maybe it was just gas related?

 

summer gas blends differ from winter...but i'm not sure which is better/worse?

No codes set or pending (I have autoxray 6000 scanner).

 

I get fuel at the same stations I always have. I have not seen a decrease in fuel economy in my wrangler and i'm using fuel from same stations.

 

Air filter was changed about a month ago.

Tire pressure Is ok.

 

Thanks

odd indeed.

 

you could have it removed and see if the mileage goes back up.

 

no one will have seen this before because the cooler can't affect gas mileage. if it was a large enough load on the hydraulic system to cause gas consumption to decrease (by 15%!) then it would also likely be damaging to the transmission - all of that "work" has to go somewhere - creating heat and stresses on the transmission...of course this is all silly and unrealistic because it's not happening - the transmission damage or loss of mileage due to the cooler.

 

you could have the brakes inspected - dragging pads (various causes of that) can cause a sudden drop in mileage with no other immediate symptoms.

 

maybe they spilled transmission fluid on the brake caliper slide pins, washing the grease out, cause the caliper to seize on the guide pins....just kidding.....

It is possible that they may have disconnected the battery to do the install. If so, the computer may have returned to its default program or tune so it may take time for it to relearn your driving habits.

Check your receipt, see what weight of oil they put in the engine.

Check your tire pressure. Shops sometimes check them by default, set them to some numbers they find someplace (which is usually a little under inflated) and kill gas mileage. Always look for the simple reasons first then go from there. Oil weight won't really have that affect.

Running AC more than normal. If Georgia has been like here, it's been a hot one already.

Did they get enough fluid back in the transmission? Do you feel it slipping at all?

Yes, they used the right oil.

 

Tire pressure is good.

 

I do not believe they disconnected the battery as the radio presents were still the same and the integrated garage remote still worked.

 

The transmission shifts better (smoother) than before the install.

 

Have not been running A/C more than normal.

 

Thanks

Go to the same station all the time. For the next three tanks keep a mathmatical record.

 

Change the air filter/fuel filter and PCV valve.

Do these have a fluid temp sensor for the tranny? I know the GM van in my driveway does. I wonder if the fluid temp would confuse the computer ? Sounds odd but this is an odd problem..

 

Did they change the tranny fluid as well or just add the cooler and top it off?

Do you have pics of the cooler and the area around it? Maybe a sensor was left unplugged ??

What is the temp in youre arear right now as the above does produce a good point to think about.

Problem is getting worse. Last fill up 13.8 mpg. It's gone down now at each fill up since having the cooler installed.

 

I have no pictures, the cooler is behind the bumper. The shop I had install it has spoken to several subaru techs at local dealers. No one can explain this - noone has any suggestions.

 

I called a subaru dealer in another state. The guy who I spoke to made this comment "I wouldn't know where to begin to troubleshoot this". that doesn't give me much confidence in subaru!

 

Using gas from same stations, in my wrangler my fuel economy has actually gone up about .5 mpg. Tribeca gone down 6 mpg.

 

Shop changed the transmissions fluid when they installed the cooler.

 

I'm told filter is part of pump - $15 part with $225 labor to replace.

 

air filter is still good, double checked that last night. Tire pressure still good, double checked that as well. Still no codes or pending code.

 

I couldn't find any info on pcv value location , etc.

 

I'm all out of options, I guess the next step is to have the cooler removed.

Edited April 9, 201213 yr by DM6156

just diconnect it and see what happens don't take it out. I bet it doesnt get better. 1000000's of these have been installed and never has anyone had mpg drop, so I think it is another issue.

 

Also it is not fair to bash someone as over the phonoe they would not know where to start. I wouldnt either unless the car was in my driveway or shop. I could rattle off quite a few things it could be, but that wouldnt be fair untill I saw the car. What I would do once it is here as opposed to the list of posabilites can be endless.

 

Good luck

PS no where do I see the usual things you do with something like this, starting with a tune up. A pcv valve. Filters.

 

 

If this has not been done, sort of a useless discussion. You need a clean baseline. I still think it was just coincidence.

air filter is good.

Fuel filter part of pump in tank - not easy swap

not sure where pcv valve is to check. couldn't find any info on location.

 

I suggested to out of state dealer taking it to them - on trip and would be in area - that's when he said he wouldn't no where to start. his words, not mine. He was even against removing cooler.

 

Regardless, I may have fixed it (silly little fix too)

 

All highway trip, 23.1 MPG. best yet. Best highway prior was 22.4

 

will check back after tank of mixed driving

Edited April 9, 201213 yr by DM6156

what did you do, did you shave some lead off your foot? tighten the loose nut behind the steering wheel?

 

My grandma used to get 23mpg in her towncar. she hypermiled it without trying. she just drove like a grandma.

what did you do, did you shave some lead off your foot? tighten the loose nut behind the steering wheel?

 

My grandma used to get 23mpg in her towncar. she hypermiled it without trying. she just drove like a grandma.

 

No hypermiling. 70-75 mph on highway (ga to nc)

2nd tank since "fix" (90% highway) was 23.2 mpg.

 

will post more after doing more in town driving.

tighten the loose nut behind the steering wheel?

 

Given the reluctance to say what he did, it looks like you nailed it

(Just kidding...)

Yo, DM! Don't keep us hanging!

I got a feeling it was something

What size was the trans cooler installed? If oversized cooler was installed, the trans fluid may not reach normal operating temp therefore overdrive never kick in.... Notice higher engine rpm @highway speed?

If oversized cooler was installed, the trans fluid may not reach normal operating temp

not if the cooler is mounted correctly, on the line that feeds the radiator, not the line leaving radiator.

 

the cooler may ''over cool'' the fluid but the radiator will heat the fluid to the correct temp and feed it to the trans.

You are correct, sir. I thought he bypassed the radiator cooler for some reason........

 

 

 

not if the cooler is mounted correctly, on the line that feeds the radiator, not the line leaving radiator.

 

the cooler may ''over cool'' the fluid but the radiator will heat the fluid to the correct temp and feed it to the trans.