i had been told by my mechanic to run 93 because its a cleaner burning fuel and would help keep the engine cleaner. after switching from 87 to 93 i did notice a increase in gas milage and the engine had a quieter sounds to it. on a recent conversation with my dad, he said running the 93 would not be good as it is a hotter burning fuel and could cause some problems down the road. he said i should go with what is reccomended in the manuel which is 89. any thoughts on this??