Never would have asked this, but my Highlander's oil cap is several inches down from open access. I have an ATF funnel that is more than long enough to reach. Since both are oil, if I use a scott towel to wipe up most of the residue on the funnel after any use, there wouldn't be any harm in using that funnel to pour in oil, would there? I would love to hear a contrary opinion if it is backed up by fact, but from my perspective, it would be the same as pouring in a single drop of motor oil into the ATF, which would hardly be noticeable.