Just a personal experience. I was at the gas station down the street last summer and my neighbor was there filling a few gas cans. I noticed that he was putting 93 octane in the cans. I asked him what it was for and he told me that it was for his B&S powered lawn mower.
99.9% of all Briggs engines are designed for regular fuel because they are often exported to other countries that don't have all the grades that we have.
He said his mower ran horribly on regular and premium seemed to fix the problem. And that not even a new plug helped. I pulled the plug on it when we got back and the frosty whiteness confirmed that it was running lean (not enough fuel).
I didn't want to rebuild a carb, and he didn't want to buy any parts so I stumbled into my garage (I went to the gas station for beer). I use MMO to soak engine parts of stuff I'm working on and so I have several gallons of it at any one time.
I put maybe an ounce in the mower tank and filled it with his premium fuel. Then I told him to tie the handle and let it run through the tank of gas. While that was going on, he went to Sears and grabbed a new plug.
New plug installed, and I removed the muffler. I rotated the blade by hand until the exhaust valve was closed. I tilted the mower 45 degrees on its side so that I could pour MMO in the exhaust port and let the exhaust valve "soak" while the engine was still warm. After an hour or so with the muffler still off, I refueled and added a little more MMO than the first time. Black stuff blew all over the concrete and there was a big cloud of minty smoke. When stuff stopped flying out, I reinstalled the muffler and he ran through the entire tank of gas with MMO.
Next day, I took some regular fuel from one of my gas can with no MMO and it started on the first pull with no knock or ping. The neighbor was happy and gave me a six pack of Blue Moon for my troubles. He saw me buy some at the gas station. It was a good thing too! I was almost out!
Cheers
99.9% of all Briggs engines are designed for regular fuel because they are often exported to other countries that don't have all the grades that we have.
He said his mower ran horribly on regular and premium seemed to fix the problem. And that not even a new plug helped. I pulled the plug on it when we got back and the frosty whiteness confirmed that it was running lean (not enough fuel).
I didn't want to rebuild a carb, and he didn't want to buy any parts so I stumbled into my garage (I went to the gas station for beer). I use MMO to soak engine parts of stuff I'm working on and so I have several gallons of it at any one time.
I put maybe an ounce in the mower tank and filled it with his premium fuel. Then I told him to tie the handle and let it run through the tank of gas. While that was going on, he went to Sears and grabbed a new plug.
New plug installed, and I removed the muffler. I rotated the blade by hand until the exhaust valve was closed. I tilted the mower 45 degrees on its side so that I could pour MMO in the exhaust port and let the exhaust valve "soak" while the engine was still warm. After an hour or so with the muffler still off, I refueled and added a little more MMO than the first time. Black stuff blew all over the concrete and there was a big cloud of minty smoke. When stuff stopped flying out, I reinstalled the muffler and he ran through the entire tank of gas with MMO.
Next day, I took some regular fuel from one of my gas can with no MMO and it started on the first pull with no knock or ping. The neighbor was happy and gave me a six pack of Blue Moon for my troubles. He saw me buy some at the gas station. It was a good thing too! I was almost out!
