I can't believe that Tesco would down grade their 99 fuel to either 97 or 98 and still advertise it as 99, because that would get them into a whole load of trouble. I noticed the difference in my motor when I upgraded from 97 to 99, and would notice the difference if the fuel had gone back to 97. I agree with you though that putting 95 in to a high performance motor which specifically states 97 or above needed if pretty stupid, what's the point in having a top motor with a sweet engine if you're going to feed it inferior fuel, that's like feeding a supermodel nothing but big macs and still expecting her to be a top piece of a$$!!