My friend has a new BMW & ran into a problem with using premium gas (91 octane) that had too much ethanol.
According to BMW the gas can have no more than 4% ethhanol. Apparently some cheaper gases have more than that, and dirties the injectors, etc. resulting in slugish performance.
By comparison, the SC430 (2002) states that the gas mixture can contain no more than 10% ethanol. My friend now has to use ultra-premium, Shell V-Power gas with 0% ethanol. Do we need to do the same? Do "better" gas mixtures improve performance?
