Oh, you will CERTAINLY feel a difference over 95 !

Over 97 not so much of course.

Yup I think I noticed that the throttle response was a bit sharper and it possibly was pulling harder. Might just be in my mind though.

Mpg might be up a couple too. This sound about right?

They always say the extra cost is offset by a little extra mpg.

As to how different it feels, mine just feels like it revs cleaner, smoother and sharper. It seems to zip away like an arrow in the intermediate gears, when you overtake, both at lower speeds and on motorways.

I don't think it is imagined!

should you stick with one or the other (99 or 95) ?? I assume no negative issues if you chop and change (sureley it just mixes together in the tank).

I think if you mix it often, the ECU doesn't get time to settle down to either, so you won't get the best benefit of the better fuel nor the cost advantage of only using the cheaper one. I got the impression it took at least one full tankful of 99 to start really appreciating it.

I think if you mix it often, the ECU doesn't get time to settle down to either, so you won't get the best benefit of the better fuel nor the cost advantage of only using the cheaper one. I got the impression it took at least one full tankful of 99 to start really appreciating it.

When I got my Octy last August, I thought that whilst idling, it revved quite high. But, being a new car and a new car to me, I thought it would settle down. It didn't.

It wasn't until I put in a tenners worth of Tesco 99 in the tank in February that the revs settled down. It was much, much quiter and that was straight after I had put the petrol in.

Later on that week, I was going to a gig at the NEC and decided to fill it up and really see how it goes and I have to say, the impression it left on me makes me think Tesco 99 is worth it over 95. The pick up, the response whilst over taking, the smoothness, I dunno, at first I thought it was my imagination, but the next time I filled up, I put 95 back in.

That was the last time I used 95. So for me, it seemed quite an immediate impact.

I think the ECU is, one might say, a creature of habit. I'd stick to one fuel or the other.

So what fuel has a high octane yet is not filled with additives that will eventually clog and deposit?

For an un-modded 1.8T RS engine, is the ECU set to expect 95 or 97 RON?