The alcohol in the gas, and the biodiesel in the diesel really wreck havoc in an old gas, or diesel tank. The cleaning qualities, strip off all of the old Varnish, sulphur, and Lead, They both seperate the fuel from the water and contaminates, and highlight any intrusion, old contamination or condensation issues. They either go into solution, or seperation. Old Diesel, solution plugs filters. Gasoline more likely seperates, and you cant burn water. Or as we have found in small systems, clogs up the jets with corrosion. Yea, It Sucks. On the East coast here in the States, as I think as in most regions, the fuel you buy all comes from the same refineries. I know I cant afford to ship my fuel from Alaska. If you buy high octane gas, when your engine does not detonate on regular, you are wasting money. regular has higher btu content, and can give you more MPG. I know it is counterintuitive but true. No snake oil for me. I have bought and sold branded and unbranded motor fuels for over 40 years. It all comes from the same refinery bulk tank. The additive of 1/10000% is a chemical marker to ensure you are paying them their juice. I laugh when I see the advertising showing the valve deposits of a well known companies advertizing. The EPA mandates Everyones gas meets their set standards. The Joke is here in the US, Try to track down who owns the pattent for the only allowed gas formulation. Here in Delaware All gas has to be of that formulation. YSMV. The only variation is for the chemical marker to ensure the big oil companies are getting their marketing cut. Of course, Here in the States WE ALL have to comply with the FEDS standard. I am sure Someone holds the Pattent for that as well.