It's purely coincidental. This is taken from another post a week or two ago - The difference between '95' and '99' fuels (and others) are a few things. Firstly, the more premium fuels have a higher octane. This makes no difference unless you are driving a 488 Pista, or a heavily tuned car. It is true that your car may run a little better (higher mpg, etc), but this is only true because a given amount of fuel has more 'go' in it - it's a moot point, as the more effective fuel, is more expensive. This difference is also quoted to be around 2%. Not worth it. The second difference is the (bio)ethanol content - E5 vs E10. E10 is the cheaper stuff, and contains, you guessed it, 10% of bioethanol. This stuff isn't the kindest to seals, hoses, etc, but unless you're driving a Mk1 GTI, you should be absolutely fine. The nicer fuels tend to have up to 5% of bioethanol in them (sometimes none), which makes them older car friendly. Finally, the premium fuels also contain additives and cleaning agents that help keep things running smoothly. This is the only real advantage of using premium fuels and, even then, can likely be achieved by using a bit of 99 once every few fill-ups. I run my car on 99 because I can. It doesn't make much sense to, if I'm honest, and I definitely wouldn't be putting tanks of the stuff through a 1.5 - total waste of money. Given that you do the miles, I'd personally put in some nicer stuff once every three fill ups. Sorted.