Given the rapidly rising cost of a litre of the stuff that makes your car go, it’s not really a surprise that I now get asked more about fuels than probably any other motoring subject. Can I make my own bio fuel? Are supermarket fuels bad for my car? Is there anything special about so called advanced fuel? So, here are a few myths dispelled, technologies explained and truths laid bare.

Is there anything special about fuel sold at a filling station, or can I just use anything that will burn?

Fuels – both petrol and diesel – have to do an awful lot more than simply burn in the engine. As they pass through the highly engineered components of the injection system, they lubricate the parts, help to keep them cool, and ideally clean them as well. Then the fuel has to have just the right characteristics to burn the way the engine designers expected, and it must not contain any chemicals that the designers didn’t expect, otherwise the emissions reducing equipment won’t work properly and may even end up damaged (as many motorists in the South East found out when Tesco had a batch of contaminated petrol). All this adds up to a very tightly defined specification that petrol or diesel must meet in order to be sold at filling stations in the UK.

The specifications – EN 228 for 95 octane petrol and EN 590 for diesel – cover things like the viscosity (thickness), the lubricating properties, how well the fuel flows and performs in cold temperature and so on. Realistically, you’re unlikely to find a substitute for petrol, but diesel engines work differently and will ignite almost any heavy oil – cooking oil included. However, fuel that doesn’t meet the specification might burn and give a reasonable performance, but you simply have no idea what long term effect the different lubrication properties, changed combustion temperature, unknown cooling properties and so on are having on your engine, injection equipment or exhaust emissions.

So, putting vegetable oil, sunflower oil or any other non standard fuel into your tank is very likely to be both bad for the environment and a recipe for a very large repair bill.

So what about all the internet recipes for recycling old cooking oil into vehicle diesel fuel?

Well, this can be a good idea provided it’s done properly. There is a specification for biodiesel as well – EN 14214, and if the oil is processed to meet that standard, you can use up to 5% of it in your diesel vehicle without any damage. If you use more than 5%, once again, if everything goes bang, the manufacturer will reject any warranty claim. There are some new vehicles – vans particularly – that have been designed to accept a higher proportion, but they are the exception. Putting a high proportion of recycled cooking oil into the tank of an unmodified car or van runs a very high risk of damaging the injectors and pump.

I see lots of comments on the internet and in the advertising material from recycling companies to the effect that “Well, they might say that, but I’ve been running my car on it for ages with no problem”. That’s OK if you want to take the risk. However, MacDonalds have just announced that they will recycle all their cooking oil into biodiesel to run their fleet of delivery vans and lorries. In order to do this they have spent a year working with the vehicle manufacturers to modify the vehicles and alter the service schedules so that the engines can cope with pure biodiesel. So, if you want to believe the garden shed re-cyclers and run your car on pure chip oil, go ahead. I prefer to follow the example of a large company and listen to the advice from the folks who make the engine.

One more point on biofuels. Some diesel available at filling stations already contains 5% biodiesel. You won’t know about it, because a 5% biodiesel mix still conforms to the EN590 standard, so there’s no special labelling. But if you go and add another 5% from the stuff someone’s brewed up in a shed, you will be running on a non standard 10% blend – and the manufacturers won’t meet any warranty claim. By 2010, all fuel, petrol and diesel, will contain 5% biofuel at the filling station pumps, so my advice is to stick with the stuff made by the oil companies and let them go green for us. You may mistrust them, the government or both, but at least you can sue someone if your engine does blow up!

What about Supermarket fuel?

Is petrol just petrol and diesel just diesel? Are supermarket fuels the same as the big name fuels at a bargain price, or do you get something extra for your money by buying a brand? Well, as with most things in life, you tend to get what you pay for.

Let’s clear one thing up straight away, lest I get sued by the combined might of Tesco, Sainsbury at al. ALL fuel sold in the UK meets the legal minimum specification. No-one is selling sub standard fuel.

However, I mentioned earlier that the fuel should ideally clean the components as it flows through them. Over time, deposits from dirt in the air and impurities in the fuel can build up on key components and lead to poor performance, reduced mpg, difficult starting and various other problems. The major oil companies add a special type of detergent to the fuel to keep things clean, but it’s not a part of the specification for either petrol or diesel, so there’s no legal requirement to add it. A basic detergent additive can add 1p or so per litre to the cost of the fuel, and if you’re selling it for a rock bottom price, you may be tempted to leave anything out that’s not absolutely necessary. That’s just what many supermarkets did – and possibly still do. As I said, it’s not substandard fuel, it just doesn’t have the extra cleaning ingredient to keep the engine performing efficiently over the long term. So, if you always use supermarket fuel because it’s cheap, but your car doesn’t seem to have the oomph it used to, your saving might have been a bit of a false economy. What can you do about it? Try a couple of tankfuls of one of the new “Advanced” fuels. Read on to find out why...

What’s “advanced” about advanced fuels?

Oil companies have made several attempts over the years to persuade us to part with more cash to make our cars go faster or further. Back in the ‘sixties, “a shot of Red X” was what you asked the pump attendant for (remember pump attendants?). This was an “upper cylinder lubricant” to help the pistons slide up and down more easily. Around the same time, Shell had a famous TV ad with two cars driving along a beach to see how much further the “Shell Mileage Ingredient” would take you. I’m not sure that Shell ever disclosed what the secret ingredient was, but it was taken off the market after a few years presumably because petrol was so cheap anyway that no-one worried too much about mpg. The ’seventies saw “high octane” fuel with ratings of 99 or even 100 and more at the pumps to tempt us, although not that many engines would benefit from anything over the 97 or 98 that was standard for the time. The banning of lead in petrol saw an end to that. Over the past decade, a host of devices and additives have been put on the market, making lots of fantastic claims. They range from special magnetic collars to pills to put in the tank. They are usually sold via “network marketing” – a variety of pyramid selling – and the “scientific testing” they proudly boast always turns out to be very unscientific. The science behind the technical explanations is a lot of mumbo jumbo, the pills are often either mothballs or a variant and my advice is to treat them with the same credibility as snake oil, magic charms or the tooth fairy.

In the past few years, BP and Shell have both introduced advanced fuels – Shell introduced “Optimax” petrol, BP have “Ultimate” petrol and diesel, and Shell have now introduced “V-Power” petrol and diesel. Both companies make great claims for the fuels, but some critics would rather see independent testing before accepting the results of the companies’ own lab reports. However, testing is expensive so it’s hard to see who would fund it. Both Shell and BP have valuable brands that they wouldn’t want to tarnish with disreputable products and both companies have been very open about what the fuels contain. And the claims do make sense – enough for Audi to pick Shell V Power diesel when they decided to enter two diesel powered cars in the 24 hour Le Mans race last year. The Audis won – a first for motor racing and diesel technology – and won again this year, fighting off competition from a team of diesel powered Peugeots. Audi engineers acknowledge that the fuel was a major factor in their success, so there does seem to be something pretty special about it.

The advanced fuels have some key features that set them apart from the standard stuff. First, the companies select top quality fuel as the basis. Crude oil is the leftover bits of a random collection of animals and plants that died millions of years ago. Being random, oils from different oil wells don’t contain quite the same combination of chemicals – some are better for refining the basic petrol or diesel than others.

Next, the fuels have either octane enhancers, or in the case of diesel, cetane enhancers. Without going into very heavy technical descriptions, the octane rating of petrol tells you how quickly and easily it burns – although contrary to what you might think, the higher the rating the slower it burns. A slow burn is good because it avoids something called pre-detonation, or pinking, and it allows a smooth transfer of power from the fuel to the piston – good for efficiency. Cetane is broadly the same sort of thing for diesel. Lead used to be used to boost the octane rating so that normal fuel was 97 or 98 octane, but once we realised that lead is good for engines but bad for brains, the lead came out and now the normal octane rating is 95. A clever (non lead) package of chemicals is used to get a higher octane rating and most modern engine management computers will automatically adjust things to take advantage of it.

For their diesel, Shell have come up with a way of synthesising a 100% cetane fuel out of natural gas – some very clever molecular engineering which gives them the ability to boost the cetane rating of the base fuel by adding a proportion of the synthetic fuel.

Thirdly, the fuels contain a really top grade detergent pack. The standard fuels contain detergent, but there are detergents and detergents, just as there’s a difference between a cheap “value” washing up liquid and the full on Fairy Liquid – they both wash dishes, but one does it much better than the other. As a result, the fuels not only keep the components clean, they will clean up any existing deposits – that’s why they’re an easy cure for the badly running supermarket fuelled car. Two tankfulls will usually do the trick, and although it will cost you around £5 a tank full more than at the supermarket pump, it’s a lot cheaper than any other cure.

Finally, the petrols have a lubricant package to help the moving parts of the engine slide up and down more easily (remember Red X?)

The result of all this? Both companies claim cleaner engines. However, BP majors on the extra mileage they reckon you’ll get by using Ultimate, whereas Shell say it’s all about extra power from the engine. I’ve been taken along a test track in a car powered by ordinary diesel, then switched to Shell V Power and there is certainly a difference in acceleration times – both in what you could feel and as measured by a lot of telemetry. Now to me, if you get extra efficiency from a better fuel or a better engine, you can use it to drive faster, or further, but not both. It all depends how you use the extra power. Shell say faster, BP say further. My view is that you could have either from either fuel. They certainly cost more than standard fuel; whether they’re worth the premium is something you’ll have to figure out for yourself. One thing does seem certain however; not all fuels are the same – and if you stick to well known names, whether it’s a supermarket or a major oil company, you do generally get what you pay for.