2002 Chevy Tahoe oil use

I have just taken a long road trip and notice that when I drive 65 mph or slower, all is well with the oil level. However, when I set the cruise control on 75 mph or faster, the oil level on the dipstick declines at a rate of about 1/8 quart per 100 miles traveled.

This sounds crazy to me and I've been questioning how this could be, but I'm pretty sure I've documented this phenomenon twice.

Any ideas? And thank you.