91 or 95 fuel for older 2 strokes

[Kevaclone]

what do you fellers recommend for my mid 80s 90hp Johnno
standard unleaded or premium?
what are the pros/cons of either?
I'm inclined to used premium but haven't as yet


Kev

[PADDLES]

91 if it's unmodified

[Noelm]

I guess as long as it is good, clean and has no Ethanol content, then any will be fine in an older carby job like you have, I doubt that you will see any real benefit in using Premium,

[sneddo]

After just buying my new 30hp mercury 2 stroke and having a long conversation with the mechanic about fuel they warned me to not use premium unleaded fuels to stick with just standard pump unleaded fuel. His reason was that premium contains ingrediants that will cause the oil in premix to separate from the fuel causing siezed motors in some cases. I have also read an article by Andrew Norton a boat and motor reivewer in many popular magazines, he has also recomended standard unleaded for the same reasons. I know that there is a product made by Bombardier that you can put into your fuel to keep it freash for up to a year and fuel/oil will not separate and go stale if left sitting for more than a month or so. I am unsure of premium use in 4 strokes but they do not premix oil.
Also some premium unleaded fuels will destroy or gum up some parts as i learnt from years of racing motorcross and with a couple of costly rebuilds because of pump unleaded fuels and their additives.

[Jock The Rock]

speaking of fuels i run premium unleaded in my 15horse 4 stroke by a mates recomendation.

he told me the other day that i should only run it every now and then because it does damage to the piston rings because of increased pressure from the larger explosion? is this bull$#!+?

i only use shell fuel as well because i was readin a previous thread on bp unleaded and ethanol

thanks for ur help

[Kevaclone]

speaking of fuels i run premium unleaded in my 15horse 4 stroke by a mates recomendation.

he told me the other day that i should only run it every now and then because it does damage to the piston rings because of increased pressure from the larger explosion? is this bull$#!+?


thanks for ur help

Your mate seems a little confused about fuel octane
there will not be a bigger explosion, in fact a high octane fuel will burn slower, this makes it easier to control the flame front and allows for more ignition advance


Kev

[PADDLES]

4s is a different kettle of fish too, there probably would be benefits in using premium in a 4s but not in a stocko 2s.

[Pelagic 660]

How about efi 2 st? any thoughts. I have a 2004 merc 150efi and run premium, but am I wasting my money?
Trevor