Why do they specify HP-ATF for the later model 4EAT transmissions?

What changed?

Is the engine torquier?

Is it just the taller stiffer low-profile tires or suspension changes?

 

I took my 2008 Forester auto in for a recall which was a trans ECU thing, and they didn't notice the fluid was turning brown, so it's not like the dealer here really gives a hoot about customer cars.

 

The reason the fluid was brown is because the children at the quick oil change place which I used one-time-only drained the tranny instead. At the time I didn't know ATF-AT was specified. They just refilled it when I could not pull out of the bay. Idiots. It was a year ago so I had no reason to drain it, and on the dipstick it was not noticeably brown.

 

I rotate tires every other oil change 6K. They appear evenly worn, although the fronts took a bit more wear this time on the inside edge. Eveything is evenly work. Yokohama Geolanders OEM. 55k miles so far.

 

The 1999 Forester fluid is fine, but hten it is down about 20% on HP due to age, I estimate. Is the HP the difference in 4EAT stress, or is it just the typical tailgating brake-jabbing American commuter Subaru has come to expect?

The Japanese spec fluid has something + in the 100 degree spec for maintaining viscosity.

Warming up the automatic transmission fluid becomes the problem.

The all wheel drive clutch pack shares the same fluid as the trany.

I assume that the clutch pack is not as kind to, or as effective with lesser fluids, especially when things heat up.

Edited May 19, 201213 yr by subaruplatt

Valvoline MaxLife is compatable with most fluids, including the Subaru fluid, and its great. I started using it in my Hyundai because the SP-III Hyundai fluid is expensive.

 

It says for vehicles over 75,000 miles, but I'm sure its fine for newer ones.

had customer who istalled wrong fluid and ruined the tranny used install was $1800. So think twice before trying a different fluid. just heads up.