I had a generac gp3300i that was shuddering and running rough. I changed the spark plug, cleaned the air filter and spark arrestor, drained fuel and added fresh and it was still running rough. I added fresh fuel with this additive and it was running strong within a few minutes. Definitely try this stuff before you clean the carb.

I got this mower curbside. It would hit on starter spray only. Rebuilt carb and mower fired right up but it struggled to get a smooth rpm plus I could hear a low knocking sound also. I thought bad motor no problem I have extra engine to swap it with. I tried Fast fix as a lark. Poured a easy ounce of Fast Fix into a very low level of gas in mower. Clamped the bail to keep it running and walked away for at least 15 mins. Checked back and you could still hear knock and stumbling rpms. Walked away for another 5 minutes and came back to a absolutely smooth running mower and the mysterious knock is gone also. Unbelievable results . This is a electric start mower that should bring me good money.

Surprise surprise... There are a lot of additives out there that only seem to subtract from your wallet. My lawn tractor had been bogging down a little coming up our hill out back. This is even with super fresh gas. I put this stuff in, ran it for about 10 minutes and then let it sit. When I used it the next day I was amazed at the difference. I'll be adding it to all my gas yard equipment from now on...

SO THANKFUL for Amazon reviewers!! I bought this item (small bottle from Wally Mart) based solely on Amazon reviews I deemed trustworthy. I've only used in push lawn mowers behind a never ending saga of despair regarding (several - far too many - mowers) since moving to New England. No gas stabilizer, winterizing, storage concerns are needed where I'm from. Mowers never get "stored" in the south... Sta-Bil first used in a 7.0HP Craftsman (take no prisoners) mower. I'd been religiously adding Seafoam Gas Stabilizer with every tank full of gas per first owner's recommendation, but mower started to choke within a year. I'd been religiously changing oil and filters, as well as adding the gas stabilizer since ownership. Sta-bil was a literal, immediate "shot in the arm" for the mower's performance. I bought this large bottle from Amazon (cheaper than Wally) for my 'new', very expensive Toro mower, also purchased used (from big box store). The oil, air filter, and blade were pristine, so I assumed caurberator and gas filter had been maintained as well. I still experienced what I sensed was some sort of hesitation (blockage) in cranking and performance. I'd been adding Seafoam to each gas fill per the advice given from Craftsman owner. I added Sta-Bil to Toro the day it arrived from Amazon.... Wow. What a difference. Immediate. Paid a nail biting price for the used mower. Beat myself up behind the decision until adding Sta-Bil. It literally made the purchase 500% worthwhile. Can only thank previous posters, and wish future buyers the same results.

Used this in my old lawnmower that would only start after at least 20 pulls. After two tanks of gas my lawnmower starts up after 1 pull