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How fuel is made

We spend a fortune on the stuff, curse when we get it on our shoes and waste a good portion of our lifetime standing in forecourts braving the elements because of it. Yet, if you were asked to explain how the petrol and diesel we fill our cars is made, would you know? Probably not.

We didn’t either, but we thought a quick trip to Shell’s Technology Centre in Hamburg to discover the answers.

The ingredients

It all starts with crude oil, a black sticky substance made up of what people in white coats call hydrocarbons ─ a compound made from hydrogen and carbon. Crude oil is essentially the remains of plants and sea creatures that died millions of years ago – dinosaurs, basically. As time went on, these fossilised remains – hence the term ‘fossil fuels’ – were buried under sediment, slowly forming rock.

After millions of years of extreme heat and pressure from all the weight of the sediment and sea above, the fossilised remains were slowly ‘cooked’, as it were, turning it into the black liquid substance we recognise as crude oil.

Can they suck it out with a big straw? 

That could work if the straw was long and solid enough to be shoved through solid rock, but companies like Shell instead prefer to use giant drills that burrow down to where crude oil has become trapped beneath non-permeable rock ─ rock that doesn’t let liquid pass through it.

These pockets, or streams, of oil tend to exist somewhere between 152 and 7,620 metres beneath the surface, so we’re talking a drill much larger than Black & Decker’s finest – usually dragged along by ship.

How do they know where to drill?

This is the multi-billion dollar question. When oil is seeping through permeable rock on land, it can be relatively easy to spot. But with 70 per cent of the earth covered by water, going round looking for puddles of crude oil is going to take a while.

At sea, a number of devices can be used to help the process although most are fairly crude, if you will excuse the pun. Sniffer equipment can be used to find traces of natural gas in seawater, for instance, but this only works if the oil is escaping its sediment prison.

Oil companies typically use two main search methods. The first involves magnetic survey equipment that can detect certain rock types at the bottom of the sea. The alternative, known as seismic surveying, uses sparking ─ a technique that bounces sound off the ocean floor, with a hydrophone sensor on the back working out how quickly the signal bounces back. Depending on the properties of the floor, it’s possible create a map and guess what’s lurking beneath it.


Assuming a crude oil deposit has been spotted, calculated to be commercially viable, sucked out of the earth’s crust and shipped to an oil refinery, now is the time to separate all the different ingredients using a process called fractional distillation. You may remember this from your school days, if you bothered paying attention.

Basically, the crude oil goes into a huge tube column thing (not the technical term) and is heated. Due to the different characteristics of each ingredient and their differing boiling points, some bits float to the top (petrol, for instance) while others, like tar, sink to the bottom. Now each ingredient can be separated.

One oil refinery can process thousands of litres of crude oil per day, according to Shell, separating ingredients that include LPG, naphtha, kerosene and gas oil. Although not all ingredients are necessary for diesel and petrol, leftovers can be used for other products such as engine lubricants and oil for heating systems. You didn’t really think a multi-billion dollar giant would let stuff go to waste, did you?


Now we have a base fuel, it’s time to start to make fuel more effective at its job. This involves development by way of finding out “how best to combine those materials produced at the refinery with other ingredients”, coming up with a new formulation blend and then putting the blend through its paces.

“Not all of the ideas will be successful, but the ones that are will go on to be researched further,” Shell explained. “A typical development process would involve extensive testing in the laboratory, in engines and in vehicles, resulting in the winning formulation being identified and defined, with robust and extensive substantiation testing.

Rigorous testing is necessary to ensure a new fuel won’t randomly combust at your local petrol station while filling up, damage your paintwork if you spill some, stain your clothes or burn your face off.

How do you blend a fuel, then?

Glad you asked. Minor ingredient changes can be made using a clever bit of software that can then calculate a fuel’s new theoretical properties. This saves Shell’s 200 dedicated fuel scientists the hassle of physically mixing together all the ingredients in the correct measurements.

Dragging a series of on-screen sliders up or down causes software to run complex mathematical calculations too difficult for our brains to fathom, allowing the scientist to see how the differing levels of ingredients will affect the end product and, just as importantly, whether it meets regulatory requirements. As each change is made, the properties are displayed pretty much in real-time ─ albeit with a momentary pause occurring as the complex calculations are crunched.

Because of rules and regulations in road and Formula 1 fuels, each new fuel needs to “meet and exceed” a lengthy number of requirements, most of which can be checked by the aforementioned software. If there’s too much or too little of a particular ingredient, for instance, the scientist will know.

Testing the mix

Eventually an actual mix is made to be tested in a fancy vehicle testing lab that can adjust temperature between extremes of hot and cold. This is done in a controlled environment using clever measuring systems we were specifically told not to take photos of. Here, Shell can work out efficiency, emissions and a whole host of other useful scientific data points to ascertain a fuel’s abilities.

To keep the testing fair – the team that performs these tests is small – new fuels are wheeled in by the barrel load without anyone having a clue as to their chemical composition. This keeps the placebo effect at bay, making the results more accurate and therefore more useful.

If you’re wondering what this area of the Shell Technology centre looks like, think of it as two rooms. One small room is filled with switches, computers and clever people looking at the results. Another far larger sealed room contains a hefty system for controlling temperature, with a bog-standard saloon car on a dynamo used for the main testing within.

Before you ask, no, a bloke who pulls the short straw does not sit in a freezing sealed room while inhaling exhaust fumes all day. A sinister-looking robot takes care of the driver inputs like acceleration.

Why go through such hassle?

A good fuel can help prevent nasty deposits building up in your engine, which may affect power output and efficiency. Petrol companies also aim to reduce engine friction and toil to create fuels that use fewer nasty ingredients like lead and sulphur, both of which are bad for the environment.

Ultimately it goes against the ethos of a company that makes money from fuels to try and make them last longer, but knowing the earth’s reserves are finite there’s every reason for Shell and competitors to eke out whatever is left.

How long does the process take?

It may seem strange that a fuel takes so much effort to design, but each ingredient could be mixed in an almost infinite number of proportions ─ with even the most minuscule adjustment changing the properties of the final fuel and therefore the effect it has on your engine, the environment, cost of production and more.

“If we were to start from scratch to develop a new formulation technology designed to meet specific performance needs, based for example on learnings from customer research, this could take many, possibly up to 10, years from conception to completion,” Shell commented.

“In Research and Development, our work is never done. We are constantly seeking the next innovation, the next breakthrough, and ways to make our fuels even better for our customers and their vehicles.”

Naturally, all that effort can be frustrating for those who spend their lives looking for that elusive blend that is a cut above the rest. As Shell scientist Valeria Loreti explained: “It’s most frustrating when a fuel makes it all the way to the final stages only to be canned.”

What about diesel?

Diesel, which gets its name from German engineer Rudolf Diesel, and not the vastly overpriced clothing brand, is made in a very similar way to petrol. In fact, the only difference is extra filtration is needed to reduce sulphur content and remove other unnecessary pollutants.

Can I put it in my car yet?!

Once a fuel is given the okay, has been shipped around the world and then driven by truck to petrol stations around the world, yes. All you have to do is fill up and, if possible, avoid looking at the scary numbers before you. It’s not called liquid gold for nothing, you know.