IF i my engine is tuned to use only 91 octane, and it says on my dash" Unleaded Fuel only", would that be a problem? im only asking this because i filled 5.12 for supereme yesterday.

 

pump gas is unleaded, in the old days gas used to be leaded, thats how they get high octane ratings and ran higher compression. race fuels are leaded mostly except for specific unleaded types. any pump fuel you buy is unleaded, you dont have to worry. it will damage the 02 sensors thats why it says that. lead exposure is also bad for your health, thats why they stopped using it.