I use rls myself but, you can use regular old Grapseed oil or sesame seed oil from your grocery store.
It's harder to filter it at the final stage but.... You also do not NEED to do anything to your oil prior to filtering... That is the point of filtering!!!!! When you filter as long as you filter everything WARM say 70-85 degree C you will knock out any bacteria or viruses or particles and things with a .22um filter.
There is no need whatsoever to use Prefiltered or even sterile oil prior to your own STERILE FILTERING hence the term STERILE FILTERING!!!
Having said that, prefiltered and USP oils tend to be and always have been with my experience... MUCH MUCH thinner cause anyand all traces of crap is filtered out making your STERILE FILTER process soooooooooo much easier!!!