I am interested in the price you have to pay for fuel in Malaysia. Here in Colorado, USA, I purchase premium fuel for $1.559 per U.S. gallon or $0.412 per liter. A young man told me recently that his price in England averages 0.82 British pounds per liter, although I do not know if this is for premium or not. This is $1.188U.S. per liter, or almost 3 times the American price.
I have used medium grade fuel and premium in my 560SEL and have not noticed a difference, either. With the price difference so low here between regular and premium, it is not prohibitive to use premium. We also have octane booster products available in this country which I haven't used but would consider if prices were to rise.
If people in other countries replied with the fuel price they pay, I'm sure that we would all be interested. Of course, fuel is just one part of the economic equation, but it is common comparison item.