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I've removed the old gas from my I/O and want to put fresh in it this weekend. The first time I took it out after sitting all winter it would die when I first throttled up on it until it got blown out. Question is: Would I be better off running a tank full of premium gas through it or would regular be just as good? With the ethanol, I'm concerned that the premium may have sat in the tank at the station quite a bit longer than the regular.
 

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I would burn nothing but regular. (Just my opinion) An outboard or inboard runs at 90 to 100% of it's rated horsepower most of the time and with the higher octane it MIGHT tend to burn valves and in the case of 2 cycle outboards (No valves) the pistons. If you don't use the boat that often try a fuel conditioner.
 

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Actually higher octane means less heat buildup... But I would burn a brand name midgrade a few times if you want the additives... It has been proven that mileage doesn't go up enuff for that to be a reason to buy premium...

If anyone wants proof that High octane is fine in high performance conditions.... just look at what is run in race cars... They wouldn't last one race on 87 octane... Thus they run 100-110 for most race vehicles, cars, cycles, boats, snowmobiles etc...
Brent
 

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If it doesn't burn hotter then why do you get ANY better millage? Tell me just how many hours does a race car last before they need overhaul? I haven't heard of many race cars going for 2 or 300,000 miles. I'll stick to regular
 

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There is <span style="text-decoration: underline;">little difference in energy content of regular versus premium gasoline. They both contain about 111,400 British Thermal Units of energy per gallon.

<span style="text-decoration: underline;">Octane is defined as a fuel's resistance to knocking. There is no benefit if the octane is higher than what the engine needs. <span style="text-decoration: underline;">Engine knock occurs when fuel in a combustion chamber ignites before it should. This disrupts the engine's operation. But electronic knock sensors are now common and have nearly eliminated engine disruption.

The <span style="text-decoration: underline;">American Petroleum Institute says if you find that your car runs fine on a lower grade, there is no sense switching to premium. The <span style="text-decoration: underline;">Institute recommends following manufacturer's recommendation, but even those manufacturers say that it is more of a suggestion than a command.

From the website of: <a href="http://www.consumerenergycenter.org/transportation/consumer_tips/regular_vs_premium.html">http://www.consumerenergycenter.org/transportation/consumer_tips/regular_vs_premium.html</a>
 

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do not compare what you know about octane ratings and how is relates to autos to marine engines guys......

being a mechanic (auto) and applying that mentality to a boat can be costly! do not use higher than the mfg recommended octane on a marine engine. ask me how I know.........I used that thought process, ONCE.......replaced the plugs (electrodes melted off) and pulled the head to replace the burnt valves.........sealarks advice was right on the money.
 
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