[ptitviet]

Hello GreenTDI! Since you are now trying to see very little differences, I think it would be interesting to do some coast down testing. It helps you to get experimental values of rolling and air resistance.

I have use the "old" method but with better tools and found SCd values accurate to 2% to the real value.

Can you show on your computer display the driving speed? Then by recording with a smartphone your screen during the coast down you can get very good accuracy.