Petrol

Here in the UK, there's now a variety of Unleaded available:

Unleaded 95 (Standard
Unleaded Plus 97
Super Unleaded 99
Super Unleaded 102

The numbers relate to the octane rating of the fuel, or rather how resistant the petrol is to early detonation or ignition if you prefer. The higher the rating, the more clean the 'shot' if you will. More powerful cars will perform better with higher octane fuel; even a normal car could well benefit.

The average UK car is rumoured to have a 1.6 litre engine. I'm guessing this is a median rather than a mean figure. Regardless, I have a reasonably nippy 1.8l Vauxhall Astra pumping out 125bhp. I like to keep it in reasonably good form under the hood, even if it is muddy on the outside from my last hiking trip.

As such, I tend to use Unleaded Plus 97. I'm not sure I noticed a massive increase in anything, though I'm fairly convinced the fuel consumption was lower. Maybe I got a few more miles out of it. However, 97 is noticeably more expensive. As such, I've decided to mix octanes (not sure if this is recommended though). I'll let you know how it goes. I might even go crazy and go up to 99, but then I doubt a 1.8l would benefit much from that sort of fuel...