the best gas fuel is Shell 91 with no ethanol addition and because the majority of the fuel is based on aromatic molecules to provide better octane rating. Often the octane giveaway in Shell V-Power is higher than 91.

Competitors don't have as much aromatic content and rely on ethanol to make up the octane, which octane numbers is a calculated number based on the volume of ethanol addition. They don't have to test the finished product, as a mathematical guess, is acceptable. So to meet the octane rating of the fuel, at the pump, more ethanol is added. That's why sometimes gas mileage varies from tank to tank.


The best reward system in Canada is Petro Canada for fuel and Shell can't compete with the discounts. Even compounded with my employees discount, Petro Canada is a better deal. Plus for me, Petro Canada diesel is better than Shells, and I get more mileage per tank. Aromatic molecules are detrimental to diesel cetane and really can cause major damage to knock and pre ignition in diesels. It's from the synthetic oil stock they use to produce fuel from the oil sands, it's full of aromatic molecules. Petro Canada uses more conventional crude in its process to produce diesel.

Wow, this turned into a lecture lol

This is based on my experiences ASTM testing of finished products and raw crude oil, over the years, and working in the field making diesel and gasoline.
The rest is just me trying to save a penny or two and get the best fuel for my dollars.