Why a diesel car costs more than a petrol version

On Tuesday, Prayas Gupta, a young design professional, sat in his Mumbai office and carefully looked at the car pricelist. Just one day earlier, Preity, his wife of three years, reminded him about their car — it was almost six years old and due for an upgrade. Gupta decided to buy a diesel and this made things more confusing. 
    Gupta looked at the list again. The Swift VXi (ABS) sported a price tag of Rs 5,25,801, while its oil-burning cousin, the Swift VDi (ABS), showed Rs 5,98,736 — a disparity of Rs 72, 935. Gupta was curious. “So, why is a diesel variant of a car more expensive than its gasoline counterpart,” he asked the retailer. 
    CV Raman, chief GM in Maruti Suzuki’s engineering division, has the answers. “In most cases, the same model usually has different engine capacities when it comes to diesel and petrol versions,” he says. “And the diesel is generally bigger.” Case in point: The Hindustan Ambassador with a 1.8L MPFI petrol engine and 2.0L diesel power plant. 
But big doesn’t always guarantee a higher price as new car prices suggest. The secret lies somewhere else. Raman also points out that a contemporary diesel engine e.g. common rail direct injection (CRDI), uses more expensive components than a similar petrol engine. “A diesel generates more heat. Unlike a petrol engine, a diesel doesn’t have spark plugs to ignite the fuel-air mixture. The ignition happens when it intakes air and compresses it. The heat of the compressed air lights the fuel,” explains Raman. So, the high operating temperature ensures that the diesel enjoys premium treatment when it comes to component quality. 
Along with expensive components, most oilburners also come fitted with turbochargers and this increases the overall price as well. A turbocharger is a forced induction system that increases an engine’s horsepower without adding too much weight. It compresses the air that flows into the engine. This means that more air can be squeezed into the cylinder, and more air means more fuel can be subsequently added to create greater power during combustion. 
    Well, so far so good. But then Gupta’s retailer also mentioned to him that the diesel Swift would ensure better fuel efficiency. And again the would-be car buyer wanted to know why. Well, this time the answer lies in the inherent quality of diesel. 
    It takes less refining to create diesel which explains its slightly lower cost. Also it is more oily and heavy than petrol for which it evaporates slowly (in fact diesel’s boiling point is higher than water). Diesel also posseses more carbon atoms in longer chains than gasoline which explains its higher energy density than petrol. This coupled with efficient engines gives diesel cars the tag of being more fuel efficient. 
    Also, in environmental terms diesel emits very low quantities of hydrocarbons, carbon dioxide and carbon monoxide — the ones responsible for global warming. The disadvantage lies in the fact that burning diesel emits high amounts of nitrogen compounds and particulate matter, also known as soot. But continuous advancements in technology coupled with ultra-low-sulphur diesel have managed to cut this down by over 90%. And if automobile experts are to be believed, this is just the beginning. 
    Also, Prayas Gupta finally bought the Swift VDi.