Ripplin said:

I have a Craftsman lawnmower. It has a Briggs & Stratton motor with a 'Fresh Start' fuel cap. The mower needs B&S fuel additive to run (stupid priority software...) and their special fuel cap has a little container filled with the additive that plugs into the bottom of the cap and sucks out drops of the additive as you mow.

Stumbled onto this while looking for something else (missed it this past summer).

I made a rather lengthy post several months ago about an older motorcycle I was selling, partly due to fuel issues - struggling with gasoline that has a percentage of Ethanol (E-10).

Fresh Start is just a fuel stablizer. Ripp's mower doesn't need Fresh Start to run, but it does help keep the E-10 gas more stable, which helps it run better. If you didn't use it, you'd see a marked decrease in performance, but it would take time. Carburetor engines struggle with E-10 much more so than injected engines.

E-10 also has a much shorter shelf life than regular gasoline. It can start to go stale in just a few weeks. That's why it's a headache for lawn mowers. The fuel usually sits much longer (in the gas can) than in a car. Personally, I use Sta-Bil, but there are others. Just make sure they are for E-10 fuel stabilization, not cleaners (those generally have alcohol, the very problem you're trying to combat).

Two thoughts on the cap dispenser.

Those are more expensive because they're a small, manufactured, application-specific piece delivering a concentrated version of the stabilizer (hence the drip application).

It's in B&S's best interest to get their customers to use the cap dispenser because customers may not always pre-mix the stabilzer\gas in their storage cans - which would lead to more engine problems - which in turn become warranty claims\customer complaints.