With just over 45K miles on the clock my 6 has never seen a drop of High Test Gas. Have treated it several times to a can of Sea Foam and I manage 38/42 MPG. Once in a while I'll experience the "famed stumble" when cold Gas, like tires, like oil, like exhausts, like wind shields, like seats, like color is a personal choice. If it makes one happy to spend the extra bucks for Premium Gas, have at it