How bad is it

I had a friend that put premium gas in his mercury 150 and it quit on him and when the mechanic took it apart he asked if he had been running premium fuel and he said “yes he had” and the mechanic told him he had burnt it up. The cylinder got too hot and fried it. So it may be true about high octane gas. I only use 87 octane in my 225 Optimax. I know my friend always used high octane gas thinking it would make the engine run better but look what happened.

The simple answer is that you were given some bad information. Running 92/93 octane will only hurt one thing, your wallet. The difference between the blends is the ability to resist pre-ignition, nothing more. Higher octane is necessary in a higher-compression motor for that very reason. But you can run 93 in any outboard all day long and it wont know any difference. If you are clever, you can switch to 93 and advance the spark a bit on the motor and pop up the torque a bit. But then you cant back off to 87 without adjusting the timing back. Ive been running 92 octane in my XR6 for 15 years now. Because I milled the heads to increase the compression which greatly improves mid-range torque. It will _not_ hurt your engine in any way except that it simply costs more. That is one of many urban legends that is simply false. Use what you can get. I have seen occasions (after Katrina for example) were I could only buy 89-92-93. Works fine just more expensive. It will _not_ make more power unless you modify the motor to take advantage of the higher octane. Increase the timing or increase the compression or both. But it absolutely will not hurt a thing. The “getting too hot” was a load of crap. Higher octane will actually lower temps because of its resistance to pre-ignition/knocking which is what ruins a 2-cycle more often than anything else when you start modifying them.2008 Pantera Classic2014 Mercury Pro XS 200

Ethanol is typically less common in higher octanes as well…Or I have been told.C.O.D. Jr. III

Hey Billius, Thank you for buying Shell! Momma needs a new pair of shoes! Daddy needs a new flippin stick! Ward, you are correct about the higher octanes and ethanol. Ethanol has a lower flahpoint than gasoline so it hurts the octane rating some. Although there is still some ethanol being blended it does usually have a lower content. I was at one time a firm believer in running 92-93 octane in everything I own from cars, trucks, boats to lawnmowers and weedeaters. I have, after talking to many “expert” wrenches been using 87 octane for quite some time. I also mix my own oil in the gas as well to make sure I keep my merc going. However, in this day and age of more and more ethanol it is probably advisable to use the higher octanes. It will lessen the effects of this ethanol craze we are experiencing to some extent. I have not experienced anything negative in my 200 merc yet due to the ethanol in the gas. Does this have something to do with the fact that I mix my oil and gas and that acts as a stabilizer? I dont know but thats kinda what Im thinking. For now Im going to keep doing what Im doing, but if I had a newer DFI motor and I was concerned about longevity I would use a higher octane gas. This is all just opinion so I guess it really doesnt mean much. Just talking about personal expereince and the little I know about gasoline blends from working at a refinery. The one thing we can all agree on is that Ethanol Sucks. It makes less power, burns less efficiently, less mpg, more pollutants in the atmosphere due to the equipment used to make the ethonal and generally more maintenance issues with whatever engine it is going through. Someone please tell me the advantage. Oh, its cheaper—NOT—you have to burn more of it so it probably costs more in the long run. Chris Coupel Paulina, La.Chris CoupelPaulina, La.