What octane do you run?

[Turbojoe78]

I have a 1998 Suzuki DT225, the service manual calls for 91 octane fuel.

My last boat had no trailer and was on a mooring so I had to buy gas on the water. From what I can remember the only option for gas was 89 octane.

I was just wondering what others who have a motor that calls for 91 octane are using, and your thoughts on using a lower than called for octane fuel in a two stroke motor.

Thanks
Joe C

 

[Bifflefan]

Re: What octane do you run?

If it says 91, you need to run 91.
They did not spends so much time developing the motor and parts to just put any old number on it. Everything is set to run at that octane.

As for not available at the dock, get a gas caddy, and haul it down to the boat. You will save money and get the correct fuel.

 

[Turbojoe78]

Re: What octane do you run?

I have this boat on a trailer so I'll be stopping at the gas station on the way to the water so getting the right octane won't be an issue.

I was just wondering what people who had to buy there gas on the water were doing.

I don't know if I would want to put 50 or 60 gallons of gas in my boat from a gas caddy, and if the marinas would let you, if they are selling gas right at their dock, then there are the environmental issues.

 

[deejaycee_2000]

Re: What octane do you run?

104 Octane

 

[mcgyver210]

Re: What octane do you run?

This is a subject I have been thinking about since my boat has always had Premium since new by the previous owner but specs say it only needs low octane.

I have been thinking of using low octane but not sure if it would hurt it since I have no experience yet with a boat motor. Although I have always been told putting High Octane in a vehicle designed for low octane isn't worth it in reality.

 

[JB]

Re: What octane do you run?

First, memorize this: Higher octane does NOT mean higher quality.

The correct octane for your engine is just like the correct size shoe for your foot.

 

[Mason M]

Re: What octane do you run?

Fuel in a gasoline motor is designed to ignite by the spark plug, unlike a diesel engine. If you have too low of an octane , the fuel could ignite by compression and not the spark plug. Signs that you are running too low of an octane , would be knocking or if you ever turned of your motor and it keeps running.
If the owner manual says 89 or 91 octane, this is what you should run. There is no benefit to running a higher octane, higher octane doesn't make the motor run better or even clean anything out. Higher octane just means that the fuel can be put under greater compression before it will spontaneously combust. so, if you are running a higher octane than you need, don't, save your money..

 

[Ernest T]

Re: What octane do you run?

I was told that higher octane fuel would have less ethanol. Fact or fiction?

 

[Mason M]

Re: What octane do you run?

Higher octane doesn't equal lower ethanol level. I don't know of any terminal in my state that sells straight gasoline anymore. All gas is cut with ethanol, in my state atleast.

 

[Ernest T]

Re: What octane do you run?

My marina claims to sell 89 octane fuel with no ethanol. Of course, I know of no way to check it, and they charge at least $1.00+ more per gal. for it. My engine seems to like it.

 

[seldomseen]

Re: What octane do you run?

see below

 

[seldomseen]

Re: What octane do you run?

Well while most two strokes have very low compression and need only low octane gas. your 4 stroke has a high compression and needs a 91 octane gas. The critical times for the 91 octane are at acceleration to a plane as the throttle is wide open and rpm is relatively low, say 3500 rpm. at idle, and also at 6000 rpm the octane requirement is lower. it is quite likely that in a pinch, fueling with 89 octane gas would not be a problem. Water skiing and towing other boats is likely a problem as your motors volumetric efficiency at those rpm's is very high which would result in high BMEP's and a good chance of preignition when using 89 octane gas

 

[eli_lilly]

Re: What octane do you run?

Well while most two strokes have very low compression and need only low octane gas. your 4 stroke has a high compression and needs a 91 octane gas. The critical times for the 91 octane are at acceleration to a plane as the throttle is wide open and rpm is relatively low, say 3500 rpm. at idle, and also at 6000 rpm the octane requirement is lower. it is quite likely that in a pinch, fueling with 89 octane gas would not be a problem. Water skiing and towing other boats is likely a problem as your motors volumetric efficiency at those rpm's is very high which would result in high BMEP's and a good chance of preignition when using 89 octane gas

DT225 = 2 stroke...

In any case, the Suzuki service manual does specifically call for a minimum octane of 91 on the 225, versus 89 for the lower HP outboard covered in the same manual.

-E