Need to buy a gallon of oil for my 1998 GTX. Just finished off a gallon of the XPS Synthetic - for $49/gallon. I know I need to find a low ash, API TC injector oil for 2 cycle engines. Are there any alternative brands that may be a bit less expensive? Also - I don't have many marina's around me - is this something I can possibly get at an auto parts store? Or am I destined to buy the XPS Synthetic?