OK bought a used lawn mower with a B&S engine. est 1995 but doesn’t really matter other than it runs well.
In a pinch, I’ve used 50:1 gas in the mower. Runs OK. I remember my Homelite saw use to run 16:1 and poorly. My 30 year old shindawa trimmer and saw ran at 32:1 and my Echo saw I run at 50:1.
Question: I can’t think of any reason not to run 50:1 gas in the B&S mower. And I prefer to keep one tank of gas rather than two tanks of gas which means I can use the gas quicker rather than let both get stale.
I do this all the time. I have run 32:1 40:1 and 50:1 in 4 stroke engines for years with no problems. My log splitter has had 40:1 put in it run and left for months before restarting again, with no problems. I do how ever run 93 in all of my small engines now. They seem to start and run better with 93. My friend runs a small lawn service and has had a lot less carb problems running 93.
I do this with my two cycle engine assortment. I mix up the gas can I fuel all of the 2-cycle engines to the mid-point of the recommended oil concentrations for the bunch. I expect the engines that require a higher concentration of oil will wear out faster, require new piston rings sooner, and the ones that require less will foul sooner, but I haven’t experienced any problems.
No problem what so ever…at least every other tankfull or so, I would run straight gas and make sure the last gas I used was ethanol free before long term storage. IMHO, that’s more important and your idea of using up gas is a good one. 2stroke oil, unlike motor oil, disperses pretty easily. I only have a problem using it all of the time in a 4stroke. One thing is for sure, any unburned gas adds a little lube to the cylinders and piston rings.
Maybe its fine but with all of the gas related small engine problems, its just not something I do. I’m very careful to use only non-oxy gas with the Briggs stabilizer all year round and that seems to work. I only mix a gallon of mixed fuel for the chain saw and weed whacker at a time and that seems to do it. If you are going to pay the same for putting oil in the gas when not needed or using a stabilizer, why not just use the Briggs stabil instead for a dollar a gallon? Just IMHO.
The problem, if any, will be deposit formation on the exhaust valve…While todays 2-stroke oils burn with very little deposit formation, after a while, deposit build-up may start to plug up the exhaust port. But 2-stroke mix does protect against carburetor gumming and varnish…
Back in the 1950s, we had a 2 stroke LawnBoy. We mixed 1/2 pint of 30 weight non-detergent oil with each gallon of gasoline (16 to 1). This mixture did smoke. However, the later 2 stroke engines I have had and used the 2 stroke oil had minimal smoke.
I wouldn’t worry about “contaminated fuel” issues in a flathead Briggs. Those things (at 6:1 compression) could probably run on kerosene if you absolutely had to. If you’re worried about ash buildup anywhere, pull the plug from time to time and check for deposits.
In fact, given the “splash-lube” nature of these engines–using a spinning oil sponged in conscription with the oil–some kind of “top oil” in the fuel is probably a good idea, in case mowing a hill temporarily suspends lubrication.
(Wouldn’t necessarily do the same with an OHV Honda, BTW…they seem more particular about a whole lot of things, including fuel.)
Outboard manufacturers got tired of having to deal with the crappy 2-stroke available in the '50’s & '60’s…So they developed their own high quality, low ash, pre-diluted oil. Gave it a rating TC-W. That let them design engines that would tolerate a 50 to 1 mixture…A few models could even use a 100 to 1 ratio…The old, antique 2-stroke engines that required a 16 to 1 fuel mix used a plain small-end wrist-pin bearing…To move up to 32, 40 or 50 to 1, the engine designs changed to include all needle and roller bearings…If they needed 16 to 1 when they were new, they still do today…