Running on empty: how it harms your car

Posted on October 4th, 2021 by GEM Motoring Assist

Running on empty: how it harms your car


The UK has witnessed scenes within the last week that have not been seen for twenty-one years. Panic buying, queues outside filling stations and frustrated motorists formed the first significant challenge for Tony Blair’s premiership all those years ago. Now, they are back. Yet, motorcar fuel systems have changed, since New Labour was in charge, and motorists who run their tanks close to empty can cause serious and expensive damage.


Better efficiency but more complication and higher repair bills

Motorcar petrol and diesel engines have become much more efficient. Unlike during the year 2000, most cars on our roads employ high-pressure direct injection. They work by pressurising the fuel before it enters the engine, increasing efficiency and reducing carbon dioxide emissions.


Yet, the fuel pumps that generate these high pressures are precision parts, with very fine tolerances. Crucially, they rely on the fuel for lubrication. Should any air enter the fuel pump, caused typically by the tank running too low, or empty, the fuel is replaced by air and the pump becomes starved of lubrication. This situation causes rapid internal wear. Unsurprisingly, they are expensive to replace.


Even if the pump does not fail immediately, the increase in internal wear rates (as pictured) is likely to cause a low-pressure fault in the future. This situation results in the engine adopting either ‘limp home’ mode, or ceasing to run altogether.


The abrasive wear particles from the high-pressure fuel pump also risk contaminating the fuel injectors. The repair costs can amount to thousands of pounds.

While this blog is not intended to encouraging panic buying, GEM thinks it essential to highlight the potential mechanical implications of driving with your low fuel level warning lamp illuminated, as well as the safety issues.