A few years ago I had a Focus td . Commuting 60 miles each way on the M4 . I tried Millers octane boost. It worked and gave a slight mpg improvement. A bottle cost £12 and by the time I had used it up over a few tankfulls I saved about £36 giving net £24 saving. A mate tried it in a Golf and he had no improvement.
In the current Plus 8 I use V-Power regularly. I was getting a “random intermittent misfire” code. In the end trying the V-Power keeps it away. I do use 95 octane if no V-Power available. I haven’t gone down the Millers route.
