Additives for Gasoline??

[HighGrass]

I love the way my Exmark runs (26HP KAW) and I want to keep it running smooth. Do any of you use a gas additive once in a while?

[General Grounds]

:blob3: i put a shot of marvels mystery in my gas tanks once or twice a month, helps keep those kohlers from tickin. tony

[Shoreline Lawn Care]

Literally a shot? I need more than that to KEEP me ticking. LOL
But seriously... how much do you add?
Thanks

[Mlc gmc03]

we have had good luck using sea foam its great stuff especially works well for all of the hand held stuff