On a bus-conversion board, I found a discussion on fuel tanks. Some buses have one, and reports of size varied from 40-100 gallons. Some buses come with two (seemingly of the same size) which vary from 30-100 gallons. (It would be awesome to have two 100 gallon tanks … As it is, we have a 60 gallon tank.) But perhaps more important for how far you can get on your tank(s) of fuel is your miles per gallon (mpg).
As for mpg, actual mileage of fully converted buses (that people have reported) go from 3-16 or so (diesel). Much of this seems to hinge on gearing and travel speed, but some is in the styles of buses, with ‘conventional’ or ‘long-nose’ chassis get better mpg than the ‘pushers’, which isn’t a surprise, as the nose is more aerodynamic than the ‘flat wall’ of the buses with the rear engine. Even with the aerodynamic issues, buses lose out in mpg because, as Mr. Jake von Slattso nicely puts it, they’re steel skin over steel supports with more steel inside, all mounted on a true medium truck chassis. Plenty heavy, but plenty safe , and with lots of space. Ours, even with the low amount of travel it gets and the much higher amount of idling is getting about 12 mpg.
In comparison, while most factory-made RVs are on lowered chassis to optimize head-space, and are built of wood, fiberglass, aluminum, and sometimes steel in order to reduce weight, they still seem to get between 2-16 mpg (diesel), with some of the newer hybrid engines hitting on that upper range. But the structural stability of these is nowhere near that of a bus, and that is not even factoring in the large slide-outs that compromise the structure as well.
So, when asked about (or confronted with a) “well, wouldn’t it make more sense to just buy an RV for better mileage?” or “don’t forget that all that weight you’re adding in tanks/walls/appliances/frippery will take away from your mileage!”, I have to take a deep breath and re-iterate that school buses are about the safest vehicles on the road. And yes, while a lightly (or under-) loaded vehicle is likely to get better mileage than one that’s fully loaded, buses with air brakes stop better when loaded, and most buses are geared low enough that the added weight really doesn’t stress the engine too much. (One guy on the Skoolie board commented that he built Jacuzzis into his buses and the mileage didn’t vary at all whether the 8/10-person Jacuzzis were full of water or empty.
We’re been exploring WVO (Waste Vegetable Oil) as a fuel source, in order to make the project more efficient in its mileage. Why WVO, you might ask? Well, most diesel engines will run on it with -no- modifications whatsoever (Apparently, there’s a type of fuel-lubricated rotary fuel pump on some engines that has an issue because the WVO is more viscous than diesel fuel). Major costs involved in the conversion are auxiliary fuel tanks, a fuel tank heater (WVO needs to be at about 160 degrees to flow like cold diesel), a flow switch/ electric valve and possibly new, corrosion-resistant fuel lines.
There is a filtering/ settling process to actually get the WVO to be usable (though some don’t worry about this – which may or may not damage the injectors), but you end up with a cleaner burning fuel that smells like french fries (or probably in our case, wings). There’s an outfit in Mississauga, Ontario that makes in-line pressure-driven centrifuges that would take water and particulates out of the WVO.
I’ve asked on another board how the mileage with WVO compares with diesel, and it seems like WVO should give about 80% the power of diesel. I’ve been toying with getting another tank to get 50-100 gallons worth of travel of our trips for just the labor and filters of processing out the sludge from the WVO – which will likely be well worth the savings at the pump, since many restaurants have to -pay- to have the stuff disposed of …