6N2 sudden pinging & loss of power

[jets]

Coming home the other night from a meal out, engine working in 4th gear up a long hill, slight tapping noise then pinging & loss of power. I changed down a gear & everything settled down continuing up the hill. By now the hill had reduced resulting in less load.
It was another 6 km to our house & every was normal. The whole hiccup probably only lasted 3 or 4 secs. The fuel I use contains 10% ethanol & is classified as 94 RON & have never had a problem before. I am planning on changing the fuel filter that has done 23,000km.
Spark plugs have done similar mileage. 6N2 AHW engine.
Any ideas gratefully accepted.

[buzuki]

sounds like bad fuel batch

[jets]

Thanks, that ties in with my wife's comments when the car was last filled that it wasn't running as well as normal.