Petrol vs Gasoline: Why the Difference in the Name?

Bertha Benz drove the world’s first car on the first-ever road trip on 5 August 1888. When she stopped off for fuel at the Stadt-Apotheke (town pharmacy) in Wiesloch she turned it into the first filling station in the world.

But what did she ask for?

Ligroin”. This was heavy naptha, a distillate of petroleum oil used as a solvent, and it had been on the German market from around the 1860s.

It was rather different from the petrol you buy today. The classically educated British called it petroleum, which comes from the Latin: petra; rock, oleum; oil or literally rock-oil.

A picture of an early petrol pump on a handcart.
Early gas or petrol pumps looked like this Texaco variety

This was appropriate as petroleum was found under sedimentary rocks where countless bodies of zooplankton and algae had been subjected to enormous pressure and heat. It was fossilised fuel (and the energy was fossilised sunlight).

The first modern oil well wasn’t in Texas or Saudi Arabia, but at the Riddings colliery at Alfreton, Derbyshire. In 1847 a chemist, James “Paraffin” Young noticed a seepage of oil and managed to distil from it a light oil that he could use in lamps instead of expensive whale oil.

His patented discovery probably saved whales from total extinction. Different fractions of the distilled product were useful for different things: paraffin for lamps and the more volatile petrol as a solvent or fuel.  

The Americans called the fuel gasoline, or confusingly “gas” for short, a name which comes from the British coffee merchant and Temperance publisher John Cassell. Seeing new opportunities for artificial light, in 1862 he set up an oil refinery in Hanwell, London and marketed his new lamp fuel under his own name:

“The Patent Cazeline Oil, safe, economical, and brilliant … possesses all the requisites which have so long been desired as a means of powerful artificial light.”

The Times, 27 November 1862

Sales boomed, then fell away in Ireland. Cassell found out that a Dublin shopkeeper, one Samuel Boyd, was selling counterfeit Cazeline Oil and asked him to stop. The shopkeeper responded with a paintbrush, changing every label to read “Gazeline”, coining a word that eventually spread throughout the USA. Cassell took him to court and won, but Boyd’s coinage won in the end: “gasoline”.

A photograph of a vintage Shell Gasoline pump
“You can be sure of Shell”

So the Americans called the fuel gasoline, or confusingly “gas” for short.

A photograph of a large red gasoline tanker
Gasoline was trucked around the USA by this 1934 Ford Tanker

Karl Benz knew that his engine had a limit, and that limit was called detonation. Combustion in petrol engine is initiated by the sparking plug at a specific point in the piston’s travel; between 0 to 40 crankshaft degrees before the piston comes to the top of its stroke (Top Dead Centre).

The flame front should spread smoothly, burning all the fuel/air mixture just in time to push the piston back down the cylinder. But when pockets of fuel/air mixture explode early detonation occurs. The shockwave causes the characteristic knocking or pinging sound as combustion pressures rise sharply.

The results can be disastrous: first overheating and then the erosion of holes in the piston or cylinder head. Old-time engineers could detect the onset of detonation by holding a short piece of steel between their teeth and resting the other end on the cylinder head of an engine running at full throttle.

That’s why they didn’t have many teeth.

When used in Benz’s engine ordinary chemist’s shop petroleum worked well enough until the engine’s compression ratio was increased beyond around 3.2:1. This ratio is a measure of how tightly the fuel and air mixture is squeezed in the cylinder.

More accurately it is the ratio between the volume of the cylinder plus the combustion chamber when the piston is at the bottom of its stroke, and the volume of the combustion chamber when the piston is at the top of its stroke.

If Benz’s one-litre (actually 954cc) cylinder drew in a deep breath of one litre of air/fuel mixture it could safely compress it to only a third of the volume. Any higher ratio and detonation would set in.

The photograph of a Benz engine
The Benz engine burned “Ligroin”. This was heavy naptha, a distillate of petroleum oil.

Modern car engines use a compression ratio of around 10:1 because there are huge gains in power and thermal efficiency to be had.

The Rolls Royce Silver Ghost made around 48 horsepower from over 7 litres, a pitiful 6.8 hp per litre, whereas a modern General Motors LS 7 litre engine of the same capacity, with an 11:1 compression ratio, makes 505 horsepower.

A picture of a large blue Rolls-Royce
A 1914 Rolls-Royce Silver Ghost

That’s 72 hp per litre, or more than ten times as much. A lot of the difference has to do with the advances in fuel because they enabled higher compressions to be used.


Fuel quality was therefore of vital importance to the motor industry once it was known how much more power could be had.  How could they improve the fuel? Petrol’s resistance to detonation is measured in octane number: the higher the octane number the more compression the fuel can withstand before detonating.

Benz Patent-Motorwagen would have been running on Ligroin of about 40 octane, and during the First World War, aircraft engines would have used petrol of around 50 octane. But petrol bought in a supermarket petrol station today might have an octane rating of 95 or so. 

A photograph of a large red Texaco gasoline tanker
The gasoline shipped in this 1934 Ford Tanker would have had an octane of only 40.

And if the octane number is increased from 72 to 100, the power is likely to increase by 100 per cent.

Low-octane fuel nearly brought disaster to the Allies during the First World War. Before the American entry into the war, their European Allies used petrol distilled from crude oils from the Far East which gave acceptable performance in their aircraft engines.

When the United States entered the war in April 1917 the U.S. became responsible for supplying petrol to the Allies and suddenly a decrease in engine performance was noticed. Engines gummed up and sparking plugs fouled. If full throttle was used detonation set in and a number of aircraft were lost.

Panicked messages were sent across the Atlantic and it was found that petroleum from aromatic and naphthenic base crude oils was superior. These came from California, South Texas, the Mexican Gulf and Venezuela.

A photograph of a Gulf Oil pump
“Gulf Oil: the gas with guts.”

Exotic fuels were cooked up for the Schneider Trophy Rolls-Royce R engines by Rodney Banks, a British fuel chemist working for the Anglo-American Oil Company. The winning engine of 1929 ran on 78% benzol, and 22 % Romanian petrol with a dash of tetraethyl lead, and it developed 1900 hp with high supercharger pressures.

In 1931, when the Trophy was won for perpetuity, the fuel chemists concocted a brew for a world speed record attempt consisting of 60% methanol, 30 % benzol and 10 % acetone, and the Rolls-Royce testers were able to screw up the supercharger pressure to make a staggering 2530 hp.

These exotic brews were impracticable for military use, being expensive and unstable. Petroleum had to be made with a higher octane rating, and this is where Thomas Midgley Jr. comes into our story. 

Midgley was an American engineer working for General Motors whose assistants T.A. Boyd and Carroll A. Hochwalt undertook the first tests of tetra-ethyl lead (TEL) in 1921. They discovered that adding tetra-ethyl lead (TEL) to petrol prevented, or at least delayed the onset of detonation or knocking in engines.

A photograph of a Texaco pump
Observe the warning: contains lead…

His team had an engine on the test rig running under detonating conditions when suddenly

“The ear-splitting knock of their test engine turned to a smooth purr when only a small amount of the compound was added to the fuel supply. and all the men danced a non-scientific jig around the laboratory.” 

Thomas Midgley Jr.quoted in Nickerson, Stanton P., “Tetraethyl Lead: A Product of American Research,”

Midgley took the credit, writing to his old professor:

“We have recently discovered a new antiknock material approximately 50 times as powerful as aniline and which proves to be 100 % practical and commercial. In fact, our wildest dreams of success on this problem are exceeded by this new material. ‘Allah is good.’”

Letter, T. Midgley to Prof. H. Diederichs. Dec. 14, 1921. T

The TEL certainly increased the octane number. The problem was this compound was highly poisonous and they knew it. Indeed, it had killed several German scientists who had experimented with the stuff. (source: jalopnik)

All mention of lead was omitted from publicity materials, but Midgley became ill from lead poisoning. He had to drop all his work in 1923 and take a long vacation in Miami.

General Motors created the Ethyl Corporation and built a plant in New Jersey to mass produce the stuff. Workers suffered hallucinations, insanity and five deaths.

To prove his compound was safe Midgley participated in a press conference in 1924 at which he poured TEL over his hands, placed a bottle of the chemical under his nose, and inhaled its vapour for 60 seconds, declaring that he could do this every day without succumbing to any problems.

Shortly afterwards he had to take an absence from work again after being diagnosed with lead poisoning. The State of New Jersey ordered the plant to be closed a few days later.

Still, the profit motive prevailed and what little regulation there was in the US was ineffective. TEL was manufactured and spread worldwide as a constituent of high-octane petrol, releasing large amounts of lead into the atmosphere and causing countless cases of brain damage, particularly among children.

A photograph of a Pure Gasoline pump
Maybe not that pure…

Not content with that, Midgley was on the General Motors team that invented Chlorofluorocarbons (CFCs) for air conditioners and refrigerators under the name of Freon, which was later implicated in the destruction of the ozone layer of the atmosphere.

Once again Midgley flamboyantly demonstrated the safety of his lethal brew, this time in front of the American Chemical Society, by inhaling a breath of the gas and using it to extinguish a candle.

Midgley was highly decorated for his work before it was discovered to be so diabolical, and he was duly elected the president and chairman- of the American Chemical society.

Midgley has been described as the single organism that has had the most negative impact on the world’s atmosphere, ever, and Bill Bryson wrote in 2003 that he possessed “an instinct for the regrettable that was almost uncanny.” 

Environmental protests prevailed and after lead in petrol was banned a 2011 study by the California State University found that

“ridding the world of leaded petrol … has resulted in $2.4 trillion in annual benefits, 1.2 million fewer premature deaths, higher overall intelligence and 58 million fewer crimes”.

California State University

Once again, thanks to scientists and experts who spotted the ozone hole caused by CFCs, another Midgley menace was eradicated. In 2007, 200 countries agreed to eliminate hydrochlorofluorocarbons entirely by 2020.

Synthetic fuel might become important in the future, and might delay the extinction of the piston engine. Porsche, like all other conventional car manufacturers, has a huge vested interest in the piston engine.

The company is planning to produce their own synthetic fuel in Chile on an industrial scale, using wind power to make the stuff. Porsche’s boss Frank Walliser explained:

“The general idea behind these synthetic fuels is that there is no change to the engine necessary….It has no impact on performance – some horses more, so it’s going in the right direction – but emissions are way better; we see less particles, less NOx…In a well-to-wheel consideration, it is on the same level as an electric car.”

Frank Walliser, Porsche

A piston engine on the same level as an electric car? That’s quite a claim, and it may take a few years to work out the true costs.

The question remains: where now for gasoline-powered vehicles?

A photograph of a large red Texaco gasoline tanker with a semaphore hand out
Which way now for gasoline?