Amid rising fuel prices and a cost of living crisis, more and more drivers are trying to maximise use of the fuel they buy. However, a common mistake while fuelling up vehicles could lead to serious damage resulting in repairs costing thousands of pounds.
A diesel engine specialist has warned drivers that continuing to fill their tanks beyond the pump's initial click may cause substantial harm to vehicles and result in costly repair bills.
Aldis Ozols, CEO and Founder of A1 Diesel, explained contemporary diesel engines feature intricate fuel systems with precise tolerances that can be compromised when motorists disregard the automatic cut-off and continue pumping.
Ozols cautions: "Diesel fuel tanks contain an integrated vapour recovery system that needs air space to function properly. When you push fuel in after the first click, you flood this system which can damage the charcoal canister and create fuel pressure issues."
Ozols observes more recent vehicles face the greatest risk as they employ advanced emission control systems that may malfunction when fuel backs up into vital components. The warning is supported by industry statistics which reveal more drivers are attempting to maximise their fuel expenditure amid climbing diesel prices.
The automatic shutoff feature in fuel pumps is engineered to halt when the tank achieves its safe capacity, aligning with safety protocols detailed in guidance from the Process Safety Leadership Group.
Ozols explains: "The first click works as a safety feature, not just a suggestion. Today's diesel vehicles use high-pressure common rail systems operating at up to 2,500 bar pressure, which need clean fuel systems without contamination."
Motorists could face hefty repair costs for damaged fuel systems. Replacing a contaminated charcoal canister could set you back between £200 and £400, while more extensive damage to fuel injectors or high-pressure pumps could cost upwards of £3,000.
Ozols says: "Diesel fuel expands about 0.7% per 10°C temperature increase. If you fill beyond capacity on a cold morning, that fuel expands as it warms up and needs somewhere to go, which means it floods critical systems."
Many motorists who regularly overfill their tanks notice persistent check engine lights, reduced fuel efficiency, and in severe cases, complete failure of the emissions system.
UK safety organisations emphasise the importance of adhering to designed capacity limits. Studies indicate that ignoring engineered safety margins leads to cumulative damage that worsens over time.
"Modern diesel engines have what we call 'tight tolerances' where components fit together with minimal clearance," Ozols explains. "These precision systems work well when treated properly but break quickly when abused."
The proper method for filling a diesel tank is straightforward yet vital. Ozols' advice? "Stop at the first click, hang up the nozzle, and avoid the temptation to round up to the nearest pound or squeeze in extra fuel."
He says: "Some drivers think getting that extra bit of fuel saves money or time, but that short-term thinking creates long-term costs. That first click is your protection against expensive repairs."
The diesel expert suggests consulting your vehicle handbook for manufacturer recommendations, as particular models are even more vulnerable to overfilling than others.
Ozols says: "Think of that automatic click as your tank telling you it's at optimal capacity. Ignore this signal and you risk turning an £80 fill-up into a £3,000 repair bill."