1999 3.0 liter mercruiser motor

[fredsearay1801999]

what is the best octane gas to use with this motor.is it better to use premium gas or just the standard unleaded?
thanks
Fred:smt001

 

[por2gezo]

Just use the the boat asked for. I believe its 87 octane. I typically use 92 if its been sitting and 87 then their after.