here is the simple theory behind octane numbers --
"Petrol's octane rating is a measurement of the fuel's ability to resist engine knocking. Knock occurs when the fuel-air mix in the cylinder explodes instead of burning in a controlled way. This shockwave moves within the combustion chamber, and creates a metallic 'pinging' sound. Thus an octane rating is often referred to as an 'anti-knock index'. If fuel has a high octane number, it will have a higher resistance to engine knocking."
So to answer your question, it won impact engine if you upgrade and start using high octane petrol... only point i wld suggest is make sure you are almost empty when change fuel octane...