Tosser is a small petroleum company that operates a filling station in Montgomery, San Andreas and fuel pumps attached to The Welcome Pump Bar in Dillimore, San Andreas. It is a very small company with the above locations being it's only known business locations. It, like Gasso, is a small-time player in the petroleum refining and sales industry only maintain a very small business presence. It is unknown whether Tosser has it's own refinery or not but it may make use of the large Green Palms refinery and Octane Springs oil fields.
It's filling station in Montgomery is inaccessible to the player. The filling station has numerous Carcer City gas canisters on its property as well as a dumpster with the text Skip Here (also on the rusty wheelchair on the dock at Fisher's Lagoon). It also has a 'beater' Sadler parked behind it, and a Bike under its garage roof.
The word tosser is British slang which is the equivalent of jerk-off in America, someone who's an idiot or a frequent masturbator.