Regular Vs. Premium Gas $$$

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Mar 14, 2006
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Wilmington, NC
Do you guys put regular or premium gas in your boats?? I've always put premium in mine as that is what my Dad always did. Since the gas prices are ridiculous these days, I was wondering how it would impact my engine if I switched to regular.

Any help would be great!!!

I would check your owner's manual. I know that my 2005 F250 "requires" 89 octane if I want the 250hp. If I use 87 octane, it will not hurt the engine, although their might be a slight loss of hp/ The 275 Verado is similar in this regard. I am not sure about others....

Every marina buy me seems to have 89 octane anyways, so it isn't really an issue.
As stated, some OBs are "designed" to run on 87 octane. At best, if you run an OB on higher octane, you not only are throwing your $$ away, but at worst, there is a "slight" potential you could be hurting your motor.

Higher octane ignites at a higher temperature and remember that OB are predominantly made of aluminum - in blocks, heads, and pistons. Always, always always use the octane that the manual says ... as your motor was designed and mapped (fuel controls) to burn that octane.
DaleH":mqbnq9ln said:
...Higher octane ignites at a higher temperature...

Dale's statement is perfectally correct.

But in the case of pistons and internal combustion engines, temperature and pressure go hand in hand. High octane fuels were designed to accomidate the compression generated by modern motors. Under pressure, the ignition temperature of low octane fuel/air mix in the piston bore can decrease below that of the spark plug arc temperature.

In high compression engines (like modern outboards) low octane fuel can spontaneously ignite before the compression stroke is complete. This sends the piston back the other way...out of timing with the rest of the motor and can cause bad things to happen....the least of which is "engine knock" the worst of which is metal parts sticking out of brand new holes in your power head.

In lower compression engines like (but not limited to) older outboards, using high octane fuels can throw the timing of the fuel/air mix ignition off in the other direction. The results are similar to the description above.

The moral of the story, as was said in the previous post, USE THE SPECIFIED FUEL RATING FOR YOUR MOTOR
I run 87 octane in my OX66 when it is available, and only use 89 when my dock doesn't have regular. No issues... :wink: