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Old 04-09-2012, 09:51 AM   #56
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Join Date: May 2008
Location: Indiana
Posts: 2,183
My Ride: 2003 330Ci
Originally Posted by BuddyBuddy View Post
Although my "testing" over the weekend showed less than 1% difference between "regular" and "premium" gas, others have pointed out that there are other differences and they are basically correct.
Speaking only for the US, different parts of the country get different blends of fuel at different parts of the year.
In Chicago, we get a "winter blend" that always gets blamed for an increase in fuel prices.
When the winter blend is gone, it also gets blamed for an increase in fuel prices in the Spring.

After 10 years of driving back and forth between Chicago and Atlanta, I've noticed a marked difference (10% increase) in milage once I start filling up in Southern Indiana and parts south. I do not know what is different about the fuel, but I get better milage and it is cheaper.
There a many different blends of gasoline used throughout the US. Large urban areas like New York, Chicago, Houston, Dallas, Atlanta etc use a reformulated blend for reduced emissions.
Northern and southern states have different formulations of RFG. The Reid Vapor pressure varies based on the seasons. California has their own RFG requirements.

More general gasoline info from API:

I always got better mileage on the gasoline from Arkansas and Indiana than I did on the tank when leaving Houston on my trips to Indiana. Reformulated gas in Houston was the reason.

In Indiana there are still 4 different Reid Vapor Pressure gasoline blends used based on the time of year:
Discounts on new and CPO cars.
Most Dealers offer a parts discount, BMP Design 10% off

Last edited by shanneba; 04-09-2012 at 10:08 AM.
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