I use Seafoam in all my small engine stuff. Living in WI there's always something sitting for months. Tractor sits all winter,snow blower sits all summer...chainsaw, leaf blowers, weed trimmers, etc, etc. Never have any fuel issues. I use pump premium and 1oz/gal Seafoam. Pulled the snow blower out after sitting since April? Started 1st pull. Dump a bit in the B'cuda as that will sit from Oct til Aprilish...never have issues with that either. Not sure how well it would work over multiple years(no experience) but I have confidence in the Seafoam product over many months. My chainsaw gets used maybe once/year and it always starts....I'll bet that fuel has been in there a couple years??