Pre Ignition Detonation and Low Octane Fuel

[Reck]

So I've just been on a 200 mile jaunt around the Yorkshire countryside in the E21. Lots of twisty roads and hills - great driving!

I did notice slight overheating on hills and a lack of power though. On the way home I filled up with some premium high octane and I don't know if it was just mental but the car felt WAY better, sounded better and didn't seem to overheat. Previously I was shifting into lower gears to bring the revs up and heat down on long hills but didn't seem to need this on premium.

Am I definitely experiencing pre ignition/detonation here?

Can anyone explain to me what is happening and which way I need to twist my dizzy for better running on standard?

[drjim]

To get the dizzy right you need a timing strobe. I have one in my garage that I have no need whatsoever for any more. I'll stick it in the car and you can come and get it off me tomorrow if you like.

[Reck]

Thanks for the offer Jim. I have a timing light and timing is bob on at the minute - set it a couple of months ago.

I guess I'm asking if I should advance/retard timing and by how many degrees to compensate for modern low octane fuel? Or should I stick with premium?

[nas80]

It's the colder air and you sticking higher octane helped?