It is very concentrated and not meant to keep in the tank for a long time. I'd run it when a full tank of gas will be used in a relatively short amount of time like a road trip. I try to run a can through the tank once a year thanks to the garbage fuel we have out here in CA. I've also read that the Chevron brand but specific product "Complete Fuel System Cleaner" is a decent cheap alternative as the 44K is pricey.
