Yesterday evening, I had a nice 75 mile drive (while my dash's ambient temp. indicator showed 25-28 deg F. outside over the whole trip) at constant highway speeds (70-75 mph) and while keeping an eye out for the fuzz, I still let my mind wander -- one of the things was curiousity about how warm my ATF temperature was under these conditions.

So when I got home to my garage (only 1.1 miles from the highway exit, and I drove it at about 40 mph) -- and without shutting the engine down -- I promptly grabbed my RayTek IR thermometer off the bench and reached under the car to put it up against the bottom of the transmission sump's pan.

Reading: only 62.3 C. (average of 3 times, varying only 0.2 deg., within about 10 seconds).

Why is this interesting? Because I've written on this forum cautioning folks not to assume that their ATF fluid is fully warmed up (i.e., not to assume that the hotter scale, 90 deg C, is appropriate to use) in the winter regardless of how long they've been driving). This is a good confirmation.

Yes, I use AmsOil synthetic ATF (F.Y.I.), but I don't think that's really significant. I think that the really important thing is that it's probably representative of anyone's ATF in winter. And, also by the way, this is a '93 240, and the engine uses a 92 deg C coolant thermostat, also not particularly significant but I'm reporting these details anyway.

Consider that the two scales, 40 and 90 deg C., are quite different in terms of indicating proper fluid level (recall my article in Rolling several issues ago). ~60 deg C is less than halfway between the two scales, so it's important to interpolate (viz. my article) or at least (in this particular example) average the two scales' max and min marks to know where your transmission fluid level really stands in terms of max and min.

Moral: Don't assume that your ATF is fully warmed up, and that you should use the side of the dipstick with the hotter scale, when driving in winter.

I would like to hear whether anyone else has taken their fluid's temperature and what it was (and under what conditions, etc.).

Regards to all.