Does lift reduce rolling resistance significantly?
 

I suppose it must, and that it becomes dangerous at some threshold because cars don't have wings... :rolleyes: but if I add a belly pan and add lift as a result part of my FE gain might come from reduced rolling resistance? I would assume cars are designed with the assumption their owners will speed sometimes far above 65mph... but what if I never speed and allow my car to have more lift than originally designed? I gain FE, it seems. No?

Lift exposes more tire, which is where the penalty tends to be.

Less weight on the tire leads to less rolling resistance HOWEVER the very act of creating lift causes more drag, which more than cancels out any rolling resistance reduction.

I'd think there's the circumstance where a vehicle has negative lift (downforce) and if that were to be neutralized you have reduced drag AND reduced rolling resistance... but downforce amongst our garden-variety street vehicles is quite rare.