Premium vs Regular Fuel

[Craig Kozak]

I'm sure this has come up before, so please excuse me if I'm the new guy asking an old question. But, here goes. Co-owner brother and I are debating the benefits or lack thereof of using premium grade gas in our 2002 182 BowRider with a 4.3 MerCruiser I/O engine. I won't attempt to bias this court by saying which side of the case I'm arguing, but would certainly appreciate any and all input on the matter. Thanks in advance!

 

[Todd320]

I would say neither, use Rec-90 gas, I believe it’s 90 octane, ethanol free. Here in FL they sell it at the larger stores, like Wawa, and others, have no idea about WI.

 

[blaster]

No benefit to premium fuel unless the engine is all carboned up and diesels.

 

[BEH]

I have heard in Canada premium gas does not have ethanol.
The marina where I keep my boat does not have ‘marine” gas, just “no name” gas from different suppliers.
So I have been buying premium, 91 octane but maybe not necessary.

 

[Chip S]

More important than the grade of gas is to put fuel stabilizer/ethanol treatment in the gas every time you add gas. Doing that will eliminate 99% of your fuel related problems.

Four stroke engines that do not require premium gasoline don't see a benefit from using it but there is no harm in using it also (other than to your wallet). Octane will decrease over time, however, so I would strongly suggest filling the tank with premium + fuel stabilizer before you put the boat away for the winter. Personally, if the boat is being used regularly I would use the 87 octane but if the boat will be sitting for more than a month at a time between uses I would use the 93 octane. Always use fuel stabilizer/ethanol treatment.

FYI, two stroke engines (like my Mercury outboard) that are designed for 87 octane run worse on 93 octane. The 93 octane burns cooler and the oil that is mixed with the gas doesn't burn as well. Since your 4.3L is a four stroke it doesn't matter what octane you run.

 

[Wylie_Tunes]

Pump octane is about the fuel's volatility, or in other words, how easy is it to ignite. Lower octane is more volatile, so it requires less heat to ignite. Higher octane is less volatile, so it handles more heat before igniting. Once ignited, the rate or propagation and BTU is about the same. So no performance benefits to running a higher then required octane. I would bet that that 4.3 is designed for 87. So anything higher is safe, but not needed.

Ethanol? Whole different topic. In newer boats, ethanol does not scare me. But for those that want to avoid it if possible, I suggest first make sure you are running a safe octane, before using something just because its E-0.

 

[sbw1]

If you can purchase ethanol free fuel at a marina do that. The octane will be fine for a motor that is new within the last 20-25 years. Ethanol fuel is more trouble than it is worth. Our local gas stations also sell it but in premium octane levels only. We use it in our yard equipment to avoid fuel system problems. It is worth the extra cost because of the repair bills we avoid.

 

[Thornton69]

There is more BTU's in regular 87 than there is in premium. If it was available here ethanol free and without the highway taxes, it would be my choice in our 5.7.