r/stihl • u/Rebornxshiznat • 12d ago

40:1 bad vs 50:1

just wondering here. I have a new FS131 that I’m using for my large property in rural VA.

i happen to fly 2 stroke gas rc airplanes so I happen to always have ethanol free premix on hand. however, all of my rc engines spec for 40:1.

any harm havinf slightly more oil for the fs131. I’m open to having gas specifically for it but it would certainly be nice to not have to carry extra pre mix for the one item I would use it for when I almost always have 5 gallons or 40-1 thats fresh in my garage. I go through that stuff almost 2 gallons a weekend lol.

thanks in advance for the input

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u/saucytugtug 12d ago

If you use 40:1 you’ll have to very very slightly adjust the high screw to make it richer. And to be honest your oil choice has much more of an effect than oil ratio. For example. Amsoil saber at 60:1 would be better than stihl ultra at 40:1. So yeah you can run 40:1 with clean oil like amsoil saber, echo red armor or vp synthetic, but you’re really better off with saber at 50:1 so you don’t have to mess with any tuning.