overfilled oil
 

My girlfriend couldn't read the dipstick and added too much oil to my X5 on an 1100 mile trip. It seems to have a bizarre vapor lock sort of hesitation now. If you accelerate hard it goes without hesitation, but sometimes hesitates at acceleration less than 3/4.

Why happens when a vehicle has too much oil? I'm not blaming her because I am glad she actually checked the oil.

CT

How many quarts over are you now?

The most serious consequence is that the level can rise to the point where the crankshaft dips into it, acting as a blender to whip up the oil. In that case, the oil changes colour, it gets air incorporated in it, and it loses its lubricating properties.

Check the dipstick. If it doesn't look whipped up then there is likely no consequence to minor overfilling. To be safe, you can drain it back down to the proper level, but a single quart isn't likely to hurt anything.

I think it was only a quart or so high...and is no longer now high.
As I drove the X5 yesterday I am wondering if what I noticed is more plug, airflow meter, ignition related than anything. It has 140,000 relatively trouble free miles, but I did have to do a Mass Airflow Meter a year ago and the dealer warrantied it for a year. I better get it there Monday.

I am going to change the oil today and will report on the condition of the oil. I can tell you there is no froth on the dipstick at all. The oil was pretty clean and she couldn't tell after wiping several times if it was low.