Car Using Too Much Fuel?
Find Out What’s Wrong

The lambda sensor provides real-time feedback to the ECU about combustion quality. A failed or slow-responding sensor causes the ECU to run the engine rich — injecting more fuel than necessary. Increased fuel consumption is often the first noticeable symptom before other problems develop. Replacing a faulty lambda sensor typically restores fuel economy immediately.

A severely blocked air filter restricts airflow into the engine — causing the engine to run rich as the fuel-to-air ratio becomes too high. Fuel consumption increases noticeably. Air filter replacement is one of the cheapest and most effective maintenance items — typically £10-£30 for the filter itself.

A fuel injector that drips fuel when it should be closed delivers excess fuel into the cylinder — increasing consumption and often causing rough running. On diesel engines a leaking injector can cause hydraulic lock on startup which risks serious engine damage. Injector leak-off testing identifies the fault.

Under-inflated tyres increase rolling resistance significantly — the engine works harder and uses more fuel. A tyre that is 10psi below the recommended pressure increases fuel consumption by around 3-4%. Check all four tyres including the spare. This is the simplest and cheapest thing to check first.

The coolant temperature sensor tells the ECU when the engine is cold so additional fuel can be injected during warm-up. A sensor that permanently reads cold causes the engine to run in permanent cold-start enrichment mode — dramatically increasing fuel consumption. The engine management light may or may not illuminate.