Re: Octane- A show of Hands
Originally posted by JB:<br /> 87 octane<br />87 octane<br />87 octane<br /><br />Are all better for your Merc than higher octane fuels.
Wrong<br />Wrong<br />Wrong<br /><br />In any engine, you should run the lowest octane you can get away with. Higher octane is just a waste of money and often will give you worse performance for a handfull of reasons. With the Mercury inline 6; however, 89 is the lowest you should ever use, and 92 is even better.
DO NOT use 87 octane in a Mercury inline 6 outboard motor! These things love to burn pistons, and running 87 is a sure way to do it. I can tell you from experience you DO NOT want to replace your motor because of a fueling mistake. As my original manual from 1974 states, this motor was designed to run on
90 octane regular. Even the 93 available today is **** compared to that.<br /><br />The bottom line is, all the inline 6 experts I've ever talked to - and I've seeked out many - agree that 89 is the minimum. Many, myself included, will not risk anything below 92. The difference between 87 and 89 is about 10 cents/gallon. That's $2 for a 20 gallon tank. Do you want to risk your $1500+ motor over 2 bucks?<br /><br />It is also important to remember that the first thing that happens when gas starts to go bad is it loses octane. Even in a matter of weeks, your tank of 89 can become 87. Your tank of 87 can become 85. Thus the reason 92 is better. It can lose octane and you still won't have any issues.<br /><br /><br />Edit: <br />From the manual that has been in my boat since it left the showroom in 1974:<br />
<br /><br />Alcohol for older outboards is bad. Most non-87 fuels get that way with alcohol (around here anyhow). Oil mixes well with gas, but poorly with alcohol. It's Really bad if there's water in the gas. Considering where a boat operates, that's all but certain.<br /><br />Any grade of gas should be stabilized if it isn't going to be used-up in a matter of weeks.
