Correct kind of oil and gas for 240hp efi merc engine

[Red0471]

can anyone advise me of the correct type of octane for the gas and the correct type of 2 cycle engine to run in my 2004 speedster with efi 240 merc motoer. thanks

 

[johnhibbs]

I use AMSOIL HP Injector Synthetic
http://www.amsoil.com/storefront/hpi.aspx

I use 91 octane but 89 might be fine.

 

[johnhibbs]

I'm also going to experiment with this gas additive this summer: http://mystarbrite.com/startron//content/view/93/123/lang,en/

 

[prostuff]

This is what I use. Mercury Marine Quicksilver Prermium 2-Cycle Outboard Engine Oil http://www.amazon.com/Mercury-Marine-Quicksilver-Prermium-Outboard/dp/B003OKF95O

 

[Red0471]

Ok I'll get it and thanks man

 

[biffdotorg]

The Mercury service manual recommends Quicksiver Premium Plus for the 240efi and Quicksilver DFI for the 250 Optimax. There probably isn't much difference, but I use what the manual recommends. Oil has few wrong answers, but has better ones than others. Walmart used to stock Premium Plus, but I have not seen it in quite a while. Premium is on most shelves. Gander Mountain, Cabelas and Fleet Farm in the midwest have Premium Plus always in stock.

I personally use 91 or better octane in all my performance 2-strokes, but did read in the service manual that 87 or higher is the recommendation. I would say try to avoid Ethenol and that many times requires 91. I guess I will try 87 this summer and see if I experience any knocking. If the engine is designed around 87 or better, it should not matter.

My sleds have a knock sensor allowing them to run lower octane. I don't think we have that on our 240 Merc.