William Dent Priestman and the Oil Engine

The 7th September, 2026 marks 90 years since the death of William Dent Priestman on the 7th September, 1936. William Dent Priestman was the man who invented and patented the world's first reliable and commercially successful Oil Engine in 1885.   

William Dent Priestman was born on the 23rd August, 1847 at East Mount, Sutton On Hull, East Yorkshire, England, United Kingdom.  William Dent as he was always known was a Quaker and educated at the Quaker run Boorham School, York.  Engineering was always in William’s blood and in 1864 at the age of 17 he left school to commence an engineering apprenticeship with Martin Samuelson and Company who owned the Humber Iron Works.  In 1869 he joined the company of Sir William Armstrong and Company, Newcastle to work in the hydraulic department.  This gave him a good understanding of how liquids and gases behaved under pressure and was particularly useful in his later engine designs.  In 1877 his younger Samuel became a full partner in his company at Hull, the company becoming Priestman Brothers.

William Dent had strong family and business links to Ireland and on the 18th April, 1878 in Bray, County Wicklow, Ireland, UK, William Dent married Marion Bewley who was from Dublin.  The Bewley family were one of Ireland’s leading tea and coffee merchant families that were also Quakers.

Interestingly William Dent and Francis (Frank) William Crossley (1939 – 1897) were lifelong friends, both men actually served their engineering apprenticeships under the legendary industrialist Sir William Armstrong at his engineering works in Newcastle upon Tyne.  They were pioneers in the exact same niche industry of internal combustion engines during the late 19th century.  William Dent building on ideas from Frank Crossley.

After a number of years William Dent and his company of Priestman Brothers perfected the Priestman Oil Engine that would run on paraffin.  He developed a method to heat the paraffin and inject it into a vaporiser as an atomised mist with a specially designed nozzle.  The fuel mixture vapour was then ignited by an electric spark generated by a battery and induction coil. 

In 1886, 140 years ago the Priestman Oil Engine commenced full production.  By the time production ended in 1905 over 1200 Priestman Oil Engines had been manufactured and sold around the world.

Sadly in 1895 due to lack of capital William Dent lost control of the company he founded and further development of the Priestman Oil Engine by him was cut short at the very time he was making very important progress towards his first compression ignition engine.  The company of Priestman Brothers Hull would instead concentrate on dredgers and excavators for which today they are best remembered.

William Dent Priestman has in recent years finally started to receive the credit he rightly deserves as one of the key pioneers in the development of the Oil Engine.  And I hope Frank Crossley will follow in similar proper recognition as I highly rate both men as intellectual giants of innovation in the development of the Internal Combustion Engine.

William Dent Priestman’s ideas were widely adopted by manufacturers around the world and eventually led to the compression ignition engine that is today known as the Diesel engine.  In fact he formulated how the compression ignition engine would work years before Rudolf Diesel built his first compression ignition engine of 1897.

Stevan Patterson, Castlederg Co. Tyrone.