Is using Shell V-Power once every five tanks worth it?

Is a tank of Shell petrol V power every 5th fill worth it? Does it have a decent cleaning effect over one tank of fuel? Should I go with it consistently?

What's the best quality petrol and diesel to use?

What is the best premium fuel brand for petrol and diesel?

Apart from premium fuel, how do I stop my direct injection petrol engine becoming clogged?

I've recently bought a Toyota Auris with the 1.2 turbo petrol engine (and am very pleased with it so far). I intend to keep it for a good long time; at least 10 years, ideally. I understand that direct...