Traction will be less, but for the speeds you are talking about I would imagine traction is not one of your concerns.
It can also be "sticky" - causing more rolling drag. And the way it sticks in wheel wells and along the bottom can throw off your drag coefficient.
Don't know how your test site compares with heat and air density/altitude, but it's amazing how quickly the horsepower drops off when the elevation and/or temperature increases . . .
Only been out there 5 or 6 years, sure there are others on the board that can give better/more detailed feedback.