Can you heat a Class B motorHome the sam way as a car.

If you camp with a shore power hookup a small 1500W electric cube heater will usually do the trick. I was working in my B last week with the temperatures in the mid 30's and got it above 68F so I could use some solvent glue requiring 60+ temps. One small electric $20 cube bought at Target did the trick and quite frankly never plan to camp in a B with daytime temps any colder. So, with shore power the cost is generally free to you.

We have the propane heater built-in. That too is really very inexpensive to run.