For the past few years I have started to add castor to every gallon, for added security off my engines, it also makes them last longer and I can lean on them harder without hurting them. Most fuel can benefit from adding castor especially on road engines start with adding about 1 ounce of novarossi pure castor oil, im adding 2 at the moment and am having great results. Now the fuel im running under normal circumstances does not need any more oil but iam pretty hard on my engines and lean them really far.