thegarageblog.co.uk : Rudolph Diesel would’ve been scared-silly.

In Great Britain I think it’s fair to say that overall, we enjoy moaning about things. The recent sky-high fuel prices of the summer were a prime example. I’m sure that when Diesel hit £1.35 a litre, at the local Texaco, I could barely hear the fuel pump operating over the sounds of the owners tutting as they filled their tanks.

I drive a Mercedes Vito van with a 3.0 Diesel engine , and was used to it costing around £75 to fill-up from empty. It wasn’t exactly cheap, but at least it was consistent. At the height of the fuel price rises, it once cost me £102 to fill the tank and I remember thinking that it really couldn’t get much worse. This morning I filled-up again and noticed that it was a most reasonable £1.05 a litre. To make me even happier, they were even offering a free Cadbury’s Twirl with every coffee (I declined this for dietry reasons) and just paid my £77 with a feeling of not being too ripped-off. My joy was short-lived though when I noticed that for unleaded petrol, the price was only £0.89 a litre. That’s a saving of 16p per litre or 72p per gallon! That is an extraordinary difference in price, and it’s no wonder that sales of Diesel vehicles are suffering at the moment. You’d have to drive a lot of miles to justify any savings, as many modern petrol engines are so economical. Assuming your Diesel car averages 50mpg, then £45 worth of fuel at £1.05 per litre should get you 471 miles. The same amount of petrol at £0.89 a litre, in a car that averages 40mpg would get you 445 miles. With a typical Diesel car usually costing at least £500 more than an equivalent used petrol-engined model to buy, you’d need to drive more than 20,000 miles a year before you’d see any justifiable saving.

Rudolph Diesel first demonstrated the engine that was to immortalise his name, at the World Fair in Paris in 1900. His engine was unique in that it used the heat generated from compressing air to ignite the fuel, that was injected at the end of the compression stroke. At the time, it was a lot more efficient than a steam engine, and it even ran on peanut oil, of which the modern version is Bio Diesel. It took until 1936 before a Diesel engine was fitted to a production car, and that Mercedes 260D, despite having a top speed of around 55mph was one of the most significant cars ever made.

Unfortunately, Rudolph Diesel never got to see or drive a car fitted with his revolutionary engine. On September 29th 1913, whilst on his way to a conference in London aboard the steam ship ‘Dresden’ , he disappeared overboard sometime after dinner, and was never seen alive again. His body was found by the crew of a Dutch ship some days later, and he was identified by his son from personal posessions they found on him.

The huge torque and heavy weight of these early engines meant that they were more suited to use in ships, tractors, trains and buses rather than cars, but as technology progressed, the engines improved immensely and by the mid 1980’s, Diesel powered cars were fairly common in ‘ordinary’ cars (and of course, Taxis). The executive and luxury car market however stuck to the smoother, quieter and more powerful petrol engine. Just 25 years ago, the idea of a noisy and smoky old diesel engine in an executive car was virtually unheard of. The smoky and rattly Diesel engines were totally out of character with the image of what constituted a ‘luxury car’ and as a result, most had a 6 or 8 cylinder petrol engine (or a V12 in the case of Jaguar). The majority of these struggled to better 20mpg (or 12mpg if you had an old Range Rover or V12 Jag), but were well suited to quiet, high-speed cruising. Economy wasn’t so important and the words ‘carbon footprint’ only existed in the English language in relation to a child treading in the ashes from a barbeque and walking over the cream carpet!

It was the development of the powerful and efficient turbocharged and intercooled engine that made Diesel power a viable alternative to a large petrol engine. The W210 Merecedes Benz E300 TD of 1995 was one of the first truly outstanding executive cars, that was actually better than the 3.0 petrol equivalent model. I once drove a 1998 E300TD from Stuttgart to Calais in a day, and averaged almost 40mpg despite some 130 MPH Autobahn stretches. I knew then that Diesel power was the future for executive cars, and since then, they’ve improved so much that compared to the latest BMW 530 Diesel, that Mercedes seems positively agricultural.

Some of the best executive cars and SUV’s nowadays are powered by Diesel engines and some are simply spectacular. The 4.0 TDi fitted to the Audi A8 is an absolute monster, as is the 5.0 TDi fitted to the Volkswagen Phaeton and Touareg. BMW have the 535 Diesel that isn’t far behind the petrol V10 of the M5 in terms of perforance, yet can average almost 40mpg on a run. More remarkable is the fact that the Le Mans 24 hour race in 2008 was won by a Diesel-powered Audi R10 with a 5.5 litre V12 Turbo Diesel engine. After completing 381 laps, it was still going strong and I’ll never forget the noise it made as it powered around the track. As I was camped in a muddy field about 100 metres from Arnage corner, I was kept awake by the damn things for most of the night!

I can’t help but wonder what Mr Diesel would’ve thought about the success of his patented engine design, and how terrified he might be if he was to take a quick turn behind the wheel of an Audi A8 4.0 TDi. I bet he’d have a good celestial laugh when he saw someone fill one up with unleaded petrol by mistake though! Although unleaded might only be 89p a litre, the damage it can do to a modern common-rail Diesel injection system can cost thousands to repair! Still, it keeps the breakdown services (and us) busy draining tanks and changing filters.