Best petrol

[malcolm]

Hello All, Just a quick word on this subject, on this side on the pond all you can get is fuel with 10% ethanol. At least in Ma. I also run the cheapest premium (Super unleaded) that i can find. Its a 62 OTS 3.8 and i have put over 37000 miles on it since 2012 with no problems. no pinking, no knocking, nice tickover , pulls great and starts on the button. And its has a 9.1 head on it. Just my two cents worth. RF PS and 20 mpg too!

Point is, as you say, you are using premium. Doesn't matter that it's "cheap", if it's premium it should be the right octane.
having said that, in touring France I often had to settle for low octane petrol (or run out!). Car seemed ok, I just didn't put the engine under heavy load. That is, light feet on the throttle. Then topped up with premium a.s.a.p

[Heuer]

When we toured Italy the only petrol you could buy (apart from at Autostrada fuel stations) was the lowest octane they could produce. Most pumps had a Super Unleaded nozzle but I was warned it was just connected to the same tank as the the other stuff despite the premium price. The car pinked to the tune of 'O sole mio' for the entire tour and it was such a relief to get back into France for a tank of the hard stuff. It does not help that my engine is 9.5:1 compression so I now have a switchable low octane Megajolt map for such occasions.

[max-it-out]

Hi David , could you describe the pinking noise in more detail , so the rest of us know what to look out for if we have to use lower octane stuff . Last year I experimented with more advanced timing and sometimes you could hear a slight rattle from the top of the engine at around 1500 rpm when pressing the acc pedal more than half way . Since putting it back to normal setting ( 10 * BTDC ) that noise has gone and no other unusual noises can be heard , despite using E10 95 .

[malcolm]

That rattle is the pinking noise. Fairly high pitched rattle. Retarding the ignition a tad would have fixed it. The heavy'ish acceleration you described from low revs which caused it is why, above, I spoke about "light feet" when I had to use low octane stuff.

[Heuer]

It is a metallic rattling/knocking/ticking/pinging sound which occurs when you accelerate or otherwise put the engine under load like going up a hill. Once you hear it you will know. Just because you can't hear it it does not mean it is not happening and you can hole the pistons and damage the valves. Seems a high price to pay to save a couple of quid on a tankfull