Hi,
Just wondering what the octane rating is in the U.S of your unleaded fuel.
In the U.K regular unleaded is 95 Octane and super-unleaded is 97 Octane.
All the best,Mark.

 

91 and 93 is the premium grade around here.

 

You can't compare the pump posted octane number in the US to those posted in Europe. Europe uses a different octane rating for posting on its pumps, compared to the US. Europe posts "research" octane. US posts the average of "research" and "motor" octane..... or (R+M)/2

Research octane is a measure of the fuel's ability to resist detonation, as measured through a test routine that most closely simulates "normal" driving... part load operation. Motor octane is measured using a a test routine that more closely resembles high load operation, or what you get when you push the engine to max load/WOT. Research octane can be anywhere from 5 to 10 octane numbers less than Motor octane.

Octane requirement is also heavily affected by altitude, so you may find US fuels rated at 93-octane (R+M)/2 as sea level, and fuels rated at less than 90-octane in Denver, where the altitude precludes the necessity of any higher octane.

Good reference on gasoline:

http://www.faqs.org/faqs/autos/gasoline-faq/part1/