Wow, that is a whole bunch of new information to consider. Beyond applications on older motorcycles I wasn't aware that this type of filtering system was used.
This opens up a possibility for that old carrot juicer I've been hanging onto.
More seriously I think the black diesel option would be best if you had a 275 gallon fuel oil tank strapped in the bus, as gas station waste oil tanks are usually several hundred gallons. One good hit at a gas station could pretty much get you across the country. That's cheap even if you pay for it at a rate equal to recycling companies.
30 years ago gas stations would pay 50 cents per gallon to have waste oil removed from their holding tanks, but I don't remember anyone using it for anything more than heating oil for their shops. It's probably sold back to recyclers now, much like VO being reclaimed by the sellers at restaurants.
Thanks again. There's always something new to learn. I like this idea better than messing around with solar panels and battery banks. I found Centrifuge for Dummies at Gravity Cent. Comparison | CentrifugeForDummies.com
Seemed fitting in my case.