Why you must not fill up with the wrong fuel

With many thousands of diesel-powered passenger vehicles coming onto Australian roads, instances of filling a diesel tank with petrol – or vice-versa – have become increasingly common.

Although both fuels are derived from crude oil, diesel is less volatile than petrol. It also plays a role in lubricating engine internals. Running some petrol for any length of time in a diesel engine will strip oil film from cylinder walls and cause serious damage.

Running a diesel vehicle with a full tank of petrol can cause catastrophic failure of the engine and/or the fuel system. Fuelling a petrol-engined vehicle with diesel will be inconvenient but not potentially catastrophic. The engine may run on a mix of diesel and ULP; albeit roughly and with a noticeably smoky exhaust trail. Providing the contaminated fuel is removed and the injection system flushed, lasting damage should not occur.

Not too many years ago, diesel pumps were located in isolated corners of service station driveways where they could be accessed by large trucks and the occasional 4WD. Today, low-volume diesel hoses are also found on multi-product pump sets and misfuelling has become increasingly easy.

Fuel nozzles are colour coded, with the hand-piece for the diesel pump normally black. They should also carry a plastic warning label attached to the rubber hose. Be cautious though that someone hasn’t accidentally or maliciously wrong-slotted the nozzles so a ULP dispenser is hanging where the diesel spout should be, or vice-versa.

Diesel nozzles should be too large to fit a ULP filler neck but will fit older cars that were designed in the days of leaded petrol. More significantly, the ULP nozzle will easily slip down the throat of an unprotected diesel tank.

The most important measure if you do accidentally put incorrect fuel into your vehicle is to contain it within the fuel tank – therefore:

>> Do NOT start the engine, even just to drive the car away from the pumps
>> Tell the service station attendant what had happened and pay for the fuel dispensed
>> Disconnect the battery before attempting to move the car. Switching on the ignition to release the steering lock may activate the electric pump and feed contaminated fuel to the injectors. Even a small amount of petrol ingested by a diesel can require dismantling of the complete fuel system and replacement of costly components.
>> Call your road-service provider or a tilt-tray to remove the vehicle to a mechanical workshop which can drain the tank, clean the fuel pump and replace any internal filters.
>> If you don’t notice the error until the vehicle has been driven some distance, stop as soon as it is safe to do so and call for assistance. The further you drive the more damage you will do, even to a petrol engine that has been diesel-fuelled.

The chance of incorrectly fuelling a diesel vehicle can be significantly reduced by installing one of the specially-designed filler caps now on the market. These replace the original-equipment cap and have triggers that can only be tripped by the wider diesel nozzle.

Restrictors can be fitted to older, petrol-engined vehicles to only allow unleaded fuel to be added.

Read the latest news and reviews on your mobile, iPhone or PDA at carsales' mobile site…