Looking at the Delo Spec sheets, their dedicated CNG oil seems to have lower sulfated ash content and a lower TBN than the standard HDEO. Not sure if it's a big deal in a mower, do mowers really deplete the TBN in most cases? I guess the best question is what reason do we have to change the oil in a mower, too much contamination from wear metals due lack of filtration, fuel dilution, shearing from the extreme heat of an air cooler engine, something else?