I suppose I could get one of those lowrider jumping kits as well. I saw a Mexican American guy on YouTube who had his car jumping two feet off of the ground. It seems like this might burn a lot of extra gas.

I've been doing this with work clothing that has to be just clean enough. I'm not sure how much of the cleaning is due to agitation and how much is from the time spent in warm water and soap. I do give it a little bit of hand agitation before dumping the water out.
It would be interesting to do a control batch, where one tub of clothing rides around with me and one sits in a hot sunroom or a parked car, where it would also spend lots of time in warm water, but without the sloshing of going for a drive. I generally don't have a spot like that, but I always have the car and I need to take my stuff with me.