Have Diesels Become A False Economy?

A Bosch common-rail diesel injector is inspected

A Bosch common-rail diesel injector is inspected

In the last six years all the vehicles I’ve owned have been diesels, I’ve repeatedly spoken highly of them to customers and pushed forward the benefits of diesel, but times are changing and I’m beginning to realise that petrol engines could be the way forward from now on. Are diesel cars becoming a false economy asks Hannah Gordon?

The average prices at the pumps in the Ireland is 154.9 cent per litre for Petrol and 146.9 cent per litre for Diesel so the initial expense  of a diesel appears to pay off, not only with the extra fuel economy that diesels can achieve but the lower price at the pumps.

A diesel car is a useful and economical option for company cars and vans that do very high mileages, but what about the everyday driver like you and me, are we actually getting value for money from our diesel powered vehicles?

To begin with diesel optioned cars are a lot more expensive to buy whether new or used. Take the new Audi A4 Avant, the 2.0 TDI 150 SE is €43,740 compared with the 1.8 TFSI 170 SE which is €41,660, that’s a €2,008 difference to start with. While the combined fuel consumption for the diesel is better at an average of 4.9 litres per 100 kms compared to  6.1 litres per 100kms for the petrol model but this average can be hard to achieve especially when paired with an automatic gearbox or an over ambitious right foot. It would take more than 2 years and thousands of kms for the diesel to make any economic sense.

The modern petrol engine has greatly improved in the last 5 years, manufacturers have worked tirelessly in trying to make their engines as economical yet powerful for the modern drivers needs. Many petrol engines are either turbocharged or supercharged and run direct injection, they are refined, quiet and a pleasure to drive. The fuel economy and CO2 emissions have improved vastly, mainly down to strict EU rules but this is at no cost to customer satisfaction. The modern petrol engine should now be considered, in my opinion a great substitute for the Diesel engine.

In comparison the Diesel engine has also made giant steps in recent times, gone are the days where you could hear a diesel a mile away rattling down the road emitting large plumes of carbon soiled smoke. Engines are now strangely quiet and refined, the need to hammer the accelerator pedal in 3rd gear is still required to clean the pipes out on some diesels which then leads me nicely onto the DPF’s that are now fitted on every diesel after 2008.

The Diesel Particulate Filter (DPF) has come about in the aim of reducing harmful gases into the atmosphere, from what I’ve seen it’s also highly harmful to your bank balance too. These boxes can be found connected to your cars exhaust system and filters the gases as they pass through, the DPF’s go through a regeneration process and many vehicles have bags of liquid that help clean and regenerate the DPF, this all sounds amazing when read out, in reality they become clogged too easily and are a hefty cost to the consumer. Take a BMW Mini, a replacement DPF completed by a main dealer could be upwards of €1,000.

Diesels have become so advanced that the number of sensors and valves has multiplied in recent years, this makes it costly and labour intensive to repair when things do go wrong. The turbo, Exhaust Gas Recirculation (EGR) valve, vacuum pump and fuel filters are common faults with the Diesel engine often caused by poor servicing. A Diesel engine requires a strong battery and a powerful starter motor for it to be able to start. The Injectors also have to work at high pressures.

The major problem that I have come across many times is that people use diesel cars for short journeys, this stop start commute means that DPF and EGR valves can become clogged. Diesels require long journeys to become hot and effectively burn the soot particles, they need to be accelerated hard to ultimately “clear them out”, something petrols don’t suffer from.

I’m not against diesels at all, in fact I’m a massive supporter, mainly because I do a lot of miles and value their towing power, but the emerging presence of the turbo petrol engine and the exceptional performance and economy values do make it a serious contender when choosing a new vehicle.

The amount of diesels being sold is increasing each year and this year alone 73.87%  of new cars sold were diesel. New car sales are finally growing in Ireland but I predict in the coming years that petrol and hybrid vehicles will close the sales gap, and may even overtake the diesel sales.

Going back to the million dollar question, are diesels becoming a false economy?

With the development of strong and economical petrol engines that don’t have the costly DPF’s they definitely offer more value for money for the consumer. Unless you intend in doing high mileages or towing frequently then consider the petrol derivative, you and your bank balance won’t be disappointed.


 Hannah Gordon

22nd April, 2014




Author: Hannah Gordon

A qualified mechanic with over 8 years experience Hannah’s love of cars began at a young age. Holidays and weekends were spent helping out at a family friend’s garage passing tools and making tea. You can follow Hannah on Twitter at @femalemechanic1

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