The difference of tire pressure, on my 4 seater, between 20 and 35 PSI results in 15+% reduced amp draw.
Sure, easy to see, if you have a meter installed. 
Just haven’t had the time.
Bet my new tires suck the juice. 
Might have to over-inflate them.
My new tires are “Turf” - for sure more amps than the stock 165-70-R12’s
Same Diameter too.