7 month old gas, what to do?

[dogbert]

My dealer recommended mid-range gas, but I've been using regular just fine.

[chpthril]

Chp,
Dosen't gas loose some of its octane after sitting for a while? So wouldn't you want to add higher octane fuel to even the octane out? Please correct me if I'm wrong haha I'd like to learn somthing.

Here is some info that I posted over on WW the other day. It may sound a little out of plasce, but it's easier then retyping.

"1st, the octane number has nothing to do with the "Quality" of the fuel. Octane represents the volatility of the fuel....how much heat it takes to ignite the air/fuel charge. 87oct is more volatile then 89, and so on.

2nd, Fuel is a ratio of Octane and Heptane molecules. It doesn't loose octane, but simply becomes less volatile over time, but still retains the same number of Octane and Heptane molecular (87oct is 13 parts Heptane, 89 is 11 parts, 91 is 9 parts). Octane handles ignition pretty good, but Heptane does not, so we control the ignition by changing the ratio of Octane to Heptane for engines of different compression ratios. More Oct, less Heptane for higher compression.

A fuel's Octane rating is about controlling Pre-ignition in the combustion chamber. The lower the Octane number, the more Heptane the fuel has, the more volatile it is, and the less heat it takes to ignite. HP is a result of compression, compression builds heat, heat ignites fuel. If the fuel ignites early, and on it's own, (pre-ignition, or "spark-knock") we don't get the full force pushing down on the piston to turn the crankshaft, which results in loss of power. To prevent the pre-ignition, we use a fuel with a higher octane number (less Heptane, more Octane) which takes more heat to ignite because it's less volatile. Once ignited, all have the same burn rate.

The EPA regulates the minimum standards on cleaning additives. All fuel grades will have the same, plus what the Oil co adds on it's own.

You WILL NOT get better fuel mileage or performance, or a cleaner engine by using a higher oct as the OIL Co's want you to believe, you are just increasing thier bottom line.

Byrd, you need to use what the engine manufacture recommends, fuel injection has nothing to do with it. The ECM doesn't now or care what fuel you are using. It uses a Knock Sensor to feel for vibration caused by pre-ignition. Once this is detected, the ECM will retard the timing and increase the fuel mixture to stop it. This has a direct and negative effect on performance and fuel mileage. Not to mention that pre-ignition it also damaging to the engine.

As stated, there is NO performance gain to using a higher Octane fuel then what your engine calls for, but only a negative. Increased cost, less mileage, increased emissions, cold drivability symptoms, more deposits left behind."

Let me know if this opens up more questions

[chpthril]

I looked at the manual and never found the right octane, Does anyone know what is the right octane for the MP 340?

87oct if you have a choice.

[Jason B]

If the tank was 1/2 full you may very well have a good amount of water from condensation also. I would replace the water/fuel seperator(sp?) as well.

Personally, I would get a vacuum pump and suck out as much fuel as humanly possible. Open the floor panel, disconnect the fuel filler hose and drain it as dry as possible. Why take the chance of mixing gas? It won't take more than 45 minutes to drain it. Do you know what a marine mechanic charges? If not you're very lucky. Suck it dry.

[chpthril]

If the tank was 1/2 full you may very well have a good amount of water from condensation also. I would replace the water/fuel seperator(sp?) as well.

Personally, I would get a vacuum pump and suck out as much fuel as humanly possible. Open the floor panel, disconnect the fuel filler hose and drain it as dry as possible. Why take the chance of mixing gas? It won't take more than 45 minutes to drain it. Do you know what a marine mechanic charges? If not you're very lucky. Suck it dry.

The hard part is finding a place to dispose of 18gals of gas.

[sparky216]

The hard part is finding a place to dispose of 18gals of gas.

That's what Bon-Fires are for

[wannabewakeboarder]

The hard part is finding a place to dispose of 18gals of gas.

It works good for killing those darn weeds that grow around my driveways and garages.

[dogbert]

It works good for killing those darn weeds that grow around my driveways and garages.

Gasoline contains many toxic additives that you don't want getting into groundwater.

[Jason B]

It works good for killing those darn weeds that grow around my driveways and garages.

Not a good idea.
I use my old gas in the lawnmower and weedeater. If I have a bunch I give it to my nieghbor also and he uses it in his mower also.
Don't pour it on the ground....bad, bad, bad.