well i took a huge pay cut when i was medically discharged from the army in dec and im gonna have to down grade on the fuel and fluids that ive been using and i have a few questions as to what are the negative effects from using 91 and then goin down to 87, also ive been using royal purple engine oil since the first oil change and im going to have to down grade to another oil, any tips or advice on what to switch too??