My roommate wound up driving my 2007 RX350 home from Detroit to Fairmont, MN, and then up to the Twin Cities. The transmission selector confused him (he's used to manuals; see his LJ post on the subject). He wound up driving about 1000 miles with the selector in 4, not D.

I don't think it would have made any long-term difference, but I can't quite shake the feeling it might. Comments?

 

You used more gas and added to the engine use. These are just made up guess numbers but lets say in "D" at 60 MPH the engine turns at 1,800 RPM but in 4 at 60 MPH it may turn at 2,200 RPM. So in a 1,000 mile trip you probably add tens or even hundreds thousands of extra unnecessary revolutions to the engine. But in the grand scheme of things an engine will probably will turn billions of revolutions before it is worn out. So a few thousand extra revolutions really is just a drop in the bucked and won't make much of a difference. The only way it could matter would be if it caused the engine to overheat

Your question is one reason I don't let anyone drive my car or for that matter I won't even let anyone pump gas in my car. Things could have been worst had he left the emergency brake on or maybe filled it up with diesel fuel.

 

You're good. Would be bad if he was on 3rd. Pretty sure you are not alone....got me confused, too. The 4,3 and 2 and L are for engine braking....if you wanted to.

 

or for more power, like if you were going up a steep hill. I see not reason to take it off D at all.