One time thing, it is ok. Don't make it a habit. You just going to have a little more deposit. Nothing a dose of Seafoam can't cure.

One time is ok....A million times is ok. It will never cause a problem. I run all my equipment on 2 cycle gas and have for 15 to 20 years. Never does a thing. May even help it last longer although I have no proof of that.

You ever check for carbon build up? Unless you are using synthetic oil mix, you might have carbon deposit issue.

No. The 4-cycle is so much more efficient and runs so much leaner than the 2-cycle that it doesn't even smoke on the mixed fuel. The carbon deposits in the 2-cycle are from incompletely burned fuel/oil. A 50:1 mix is basically 'top oil' for the 4-cycle. I don't regularly run 2-cycle mix in my 4-cycles, but I do add Marvel Mystery Oil (MMO) to the fuel.

Not really true though. Stihl 4Mix have major issue with mix oil that they actually have to come out with the Ultra oil for that. They even have to have procedure to decarbon the engine routinely. The true 4 cycle engines like Honda GX25, 31 and 35 don't have that issue because they don't use mix oil.

Interesting - I don't have any experience with the '4-Mix' engines although I'm familiar with the concept.

I have 5 gal of mix that I used for my LB till it died. I mix half mix and half gas in my new snapper with no problems. It does not smoke and seems to have a bit more power than straight gas. After about 10 hours I have seen on problems.

It might take over hundred hours for the problem to show up. I won't make it a habbit unless it is like you said dilute it down first.

For the original poster, if you are worry, either pour the gas mix out and dump it into your old car, or fill the rest of the tank up and dilute the mix. It is ok, I won't worry about this at all.

Sounds like an understandable mistake. Your mower will be just fine although the exhaust fumes might smell a little different. You might want to label your gas cans "Lawnmower Only" and "Chainsaw Only".