Is more expensive fuel better for your car? You've seen the TV adverts and winced at be prices on the forecourts, but are high-end petrol and diesel fuels like Shell V-Power Nitro+ worth the extra outlay? We looked at the science and delved a little deeper in an effort to figure out whether we should bother putting it into our tanks.

What is Shell V-Power Nitro+?

It's petrol – or, in the case of Nitro+ Diesel, diesel – formulated by people with enormous brains and lots of letters after their names. They are fuels designed to clean and lubricate your engine as you drive, giving your motor the potential to run more efficiently.

What is inside Shell V-Power Nitro+?

You won't find any eye of newt or toe of frog in the mixture (we think -- Shell is very secretive of its methods). V-Power Nitro+ Unleaded is spiked with a formulation called Friction Modification Technology (FMT) which, as far as we can tell, is fancy science talk for 'lube'. This particular ingredient smears itself over the moving parts of your engine, reducing friction between the piston assembly and cylinder wall by coating them with a protective film. FMT appeared in the previous generation of the V-Power fuel, but this latest version comes with 25 per cent more of the stuff.

Shell V-Power Nitro+ Diesel, meanwhile, is loaded up with what Shell says is its most powerful detergent technology to date. This additive reduces the amount of, for want of a better word, 'crap' (soot particles and such) that are formed on the tiny outlet holes in a diesel engine's injectors. Without detergents, these deposits can form, disrupting the spray pattern of fuel as it enters the engine, reducing fuel flow.

Will V-Power Nitro+ give me better performance?

It's a distinct possibility. Shell's Friction Modification Technology, or lube, helps the engine turn more freely. Less friction means less wasted energy and more power from the fuel can be transmitted to the wheels. Also, whereas ordinary unleaded fuels have a research octane number of 95 RON, V-Power Nitro+ is rated at 99 RON. This gives your engine the potential to extract more power from every swig of petrol.

One of the keys to high engine performance is an engine's compression ratio. The higher the compression ratio, the more mechanical energy it can extract from a given amount of fuel mixed with air. Unfortunately, engines that run high compression ratios are prone to a phenomenon known as knocking, where the fuel explodes inside the cylinder instead of burning in a controlled way.

Fuels with a high RON rating are more resistant to knocking, so engines can run at a higher compression ratio, burn fuel more effectively and extract more power.

Can V-Power Nitro+ increase fuel economy

This is another definite maybe. When your car leaves the factory, the surfaces of its engine are clean and highly finished. However, over time, fuel can break down, leaving carbon deposits on the fuel injectors. These deposits clog your car's injectors like a snotty nose, meaning not enough fuel flows into the cylinders.

Deposits can also absorb fuel like a sponge, meaning some of it goes to waste. Since V-Power Nitro+ can clean deposits away and prevents them forming in the first place, there is every likelihood you'll get further on a tank of fuel.

How much extra economy could I achieve?

Exactly how much fuel you can save depends on numerous factors such as your particular car, its maintenance history and your driving style. In theory, these fuels could restore your car's economy to the levels it achieved when it left the factory, but seeing as most cars don't achieve the manufacturers' quoted fuel economy at any stage of their lives, you shouldn't expect miracles.

Is V-Power Nitro+ suitable for every car?

Shell says it'll work in anything, old or new. It can help maintain the performance levels of a new car and help restore lost performance to older motors.

Should I buy Shell V-Power Nitro+?

It's your call, ultimately. The fuel does have a lot of extra bells and whistles, but that's not to say 'ordinary' fuels don't. Most of the petrol and diesel fuels sold in the UK are formulated to clean and protect your engine – even the stuff sold at supermarkets. Some fuels are better than others, obviously, but if you value performance and economy there's probably no harm in investing in a fuel you think will give you the best value for money in the long term.