Octane Rating for Speedster 150 (155 HP)

[dolinsk71]

Always used 87 octane rating (regular gas at an automotive gas station) for my 2008 Speedster 150, 155 HP, but wonder if a higher octane rating such as midgrade (89), or even premium (91) is safe to use in a 2008 model, and would give any benefits. I see that a 2012 year pamphlet for speedster 150 mentions premium gas (91) as recommended, and 87 as "minimum".

 

[Sportster-2001-951C-Stock]

Always used 87 octane rating (regular gas at an automotive gas station) for my 2008 Speedster 150, 155 HP, but wonder if a higher octane rating such as midgrade (89), or even premium (91) is safe to use in a 2008 model, and would give any benefits. I see that a 2012 year pamphlet for speedster 150 mentions premium gas (91) as recommended, and 87 as "minimum".

The bottom line answer to your question lies in the engine knock count. If the engine MPEM detects a series of knocks from the knock sensor, it will automatically retard the ignition timing to eliminate the detonation events, then occasionally add back timing until the knocking resumes, and learn/teach itself how much ignition advance is allowable based on the octane of your fuel.

This process allows your MPEM to run max advanced ignition timing while avoiding melting the pistons.

So if you have access to the knock count, then you can observe how your MPEM is reacting to the fuel quality.

 

[Ted70]

we use 95ron over here in aussie land...makes the ski run sweet...

 

[Coastiejoe]

I use 95 in my 155 as I also own a 255 SC ski. So for me infill them up at the same pump for ease. They both run great so I'm goin with the if its not broke don't fix it mentality.

 

[Dr Honda]

In the non-supercharged boats... "Mid Grade" is the best. But... they will run perfectly fine on "Regular". The Non-supercharged engines don't need +91.

 

[dolinsk71]

Thanks to all for very knowledgeable replies! This by far is my favorite forum.