- Buick Ownership
You may not notice any difference in performance or milage. You may not notice a thing. With these DI motors they will produce a lot a carbon build up. With the cleaning properties of a high test fuel it will keep the carbon build up to a minimum. Also, people read the manual and see it says 87 octane. Yes, it says 87 or higher. I have owned a total of 4 cars that have the DI motors. None were brand new. 3 had 7000 miles or less when i found them. I would bet they never had high test run in them. The chrome tip on the exhaust were as black as can be. After cleaning them and thousands of miles later they were never that black again. I do not run high test exclusively. But it is my choice Most of the time. I also run Techron fuel additive that i buy at Costco also as a cleaner.