Our first coach was a 38’ gasser with about 340 hp. Weighed about 25,000 lbs and we towed a car that weighed around 3,000 lbs.
Our current coach is a 44.25’ diesel pusher with about 410 hp. Weighs about 43,000 lbs and we a car that weighs about 4,300 lbs.
Using @Gary RV_Wizard ’s formula...