I have heard of the toilet paper oil and fuel filter. All I have heard about it is that it works. I have not heard of anyone having problems with it. I believe it is not a system one buys, but simply putting toilet paper roles into standard filter canisters that are the right size and shape and have cartridges that are removed, verses the spin-on disposable filter.

The thing I would be concerned about is particles of toilet paper working themselves through the fuel system and clogging up the injector pump.

Also, the topic thread, and much of the discussion in alternative diesel fuel is how to recycle WMO into diesel fuel. The problem with WMO is it has a large sub-micron particle load that no filter can remove, so only a centrifuge can remove it. Even then, WMO tends to have a lot of dissolved solids that can only be removed via distillation.