What is the secret to determining the level of ATF with any degree of confidence? Cold or hot, at idle or off? I changed the fluid, but the dipstick simply doesn't consistently register the level of fluid.

In idle park hot is best. Yes, you have to check it the same all the time or you will get wierd results.

Never check with the engine off. The reading is meaningless (it will appear MUCH fuller than it really is).

Part of the problem is that the fluid is relatively clear and its hard to distinguish the level on the dipstick; suggestions?

What Imdew said......idle, in park with the motor hot and use the hot marks on the dipstick.

I repeat myself - new fluid is not sufficiently opaque and is therefore difficult to see on the dipstick. Hot, idle, in park - I understand, but what about the difficulty in seeing the fluid? Any suggestions, or is there nothing else that I can do?

The biggest problem that I have found is that it is difficult to check level after adding fluid; I usually have to wait 30 minutes or more for the ATF to clear the dipstick tube.

 

For checking, just do the usual pull, wipe, insert and quickly remove. Hold the dipstick so that light glints off of the surface of the ATF on the stick. You are looking for dry stick and glinty, wet ATF.

Scratch the end of the stick with rough sand paper. Clean all the grit off and try it.

What color is your fluid? I've had trouble checking ATF too. I can't get a good reading when hot, maybe just me, so I check in park a couple minutes after a cold start parked on a level surface after shifting through R-N-D-3-2-1 leaving it in each for a couple seconds.

 

Then I pull the stick out, wipe it clean, reinsert, then pull, then with headlights on, I hold it in front of the headlight to help see level. Turn the dipstick over too and look on both sides. I basically look for the point where the dipstick goes from being completely coated to where it might just have fluid on one edge. Note there are different cold and hot markings.

 

If you just added fluid, I wait a couple minutes, then wipe dipstick off twice and read on the third pull.