I have a 97 Volvo 960 with 118K miles and over the last few years I started to see the fuel mileage drop off a little more year over year. The car before E10 use to pull 29.25-29.75 mpg and by June of this year I was getting 26.5-26.75 mpg on the highway which I blamed on the E10 gas. I did run the cheapest premium I could find for at least the last decade.
A buddy of mine ran a specialty built duel tank 6 cylinder Dodge Charger for Shell to compare their V-Power plus Nitro against a leading competitor. Each fuel tank ran on its own bank of cylinders. After 5000 miles Shell tore the engine down to compare the cleaning ability of their fuel over the competitor. You can YouTube this test if you want.
Back to me, after talking to my buddy and seeing the results I decided to throw in a bottle Techron and fill up with a tank of Shell V-Power. I took the Volvo out for a Sunday highway drive to see if this would make a difference. The car ran ok before but there was a hesitation and a slight roughness that I thought was normal for a 19 year old car with 118,000 miles. You kind of expect the car not run like it did when it was new. Somewhere between 200 and 250 miles I got my answer, the engine dramatically smoothed out. I really didn't see much of a fuel mileage increase at the time. Two and half tanks of Shell V-Power and a bottle of Techron later, I took a trip in the car. It ran like it was brand new and my fuel mileage had jumped back up to over 29 mpg on the highway.
Needless to say nothing but top tier if I can't find Shell V-Power for this car.