50:1 Or 40:1, Hmmmm
 

I have a question(s): I have '03 EC250, which I'm currently using as a jetting lab rat. While that is going surprisingly well...My service book says 50:1 fuel mixture. Should I actually run & jet it using said mix ratio, or continue mixing at 40:1? Was it designed to run at 50:1 for max power, under racing conditions? My 300 ran/runs great mixed & jetted at 50:1. Will mixing at 40:1 actually prolong engine life, or does that come with proper maintenance? Given the quality of 2-stroke oils today, I'd be inclined to think 50:1 is fine. What's the larger opinion...50:1 ok? 40:1 better, as a margin of error? Can my 250 run as crisp at 40:1, as the 300 at 50:1?

40:1 is actually leaner than 50:1 but provides more lubricating oil. Your call really - with modern oils most everyone is calling for 50:1 at a maximum, with some pumpkins listed at 60:1 I believe.

I'm ok with spooging out "some" oil, but if I'm just waisting it to no real benefit, then I'd rather run it at 50:1.

The good old oil debate. You'll open a can of worms here for sure. Everyone has their own opinion. What it really boils down to is use an oil of your choice, at a ratio of your choice, and jet the bike to that. Stick with it.

For me thats Amsoil Dominator at 50:1

Lol! That's exactly what the 300 is at, and mixed with religiously. I'm really not trying to open a can of worms, but quickly starting to fit all the puzzle pieces together and seeing a larger picture. It's expensive enough just mixing fuel & oil...Not a fan of spraying the brush with it, unless I have to:D

it doesn't matter. I put alsways 200ml in my 10L kanister and sometime I can fill it up with more than 11L and I never had a problem

Thats how I roll too. I always mix up 10L at a time. Put around 210ml of oil in. Sometimes its closer to 11L too so kind of averages out. The rest I mix in the tank itself at half way refuel stops. Close the fuel tap, fill the tank to the nearest litre and then pour some oil in and slosh it up.

I've always mixed at 36:1 and will continue to do so. Great engine life, better ring seal, and no bad effects. NO spooge with a straight silencer either, Stealth will spooge on straight gas so don't judge. Maxima once did an experiment with a radioactive tracer in the oil to follow its migration and time through the engine, and found 32:1 to 36:1 to be a good ratio.

More oil=less wear. I was running 28:1 for the last few years. Bike still runs strong, & has great compression numbers without so much as a ring change. It may be overkill, but it's cheaper than a rebuild.

I would think that engines are designed to have a standard piston to cylinder tolerance that they get from the piston maker and do not even consider oil ratios until the carb jetting comes up. They do make recommendations for oil ratios based on the carb jetting used in the supplied carbs. The oil that we use should determine the ratio because different oils are designed to work effectively in different ratio ranges. Do not use Optima or Amsoil Sabre at 50/1 because they are designed for 100/1 and anything less than 80/1 may cause excessive spooge and gum up your power valve. By the same token I wouldn't use a non-synthetic oil at ratios above 40/1 or semi synthetic above 43/1. Seems like most fully synthetic premix oils are designed to work around 50/1 (Optima and Sabre are notable exceptions) so pick the oil you like and jet accordingly.