Tuesday, March 13, 2007

Diesel or Petrol

Shame on me!!! After four years of mechanical engineering I did not know that 1 litre of diesel lets the vehicle run more miles than 1 litre of petrol. Okay. I mean I knew but not in conscious thought (whatever that is).

So when I sit down to think about cars, two advertisements flash into my mind. One is the new Indica V2 Turbo commercial, and the other is the one for the car (think it was Merc), where one line went : "Bend up ahead! Gone in a flash." Or something to the effect. Cool ads both.

So some digging and some asking around revealed this: diesel has higher specific heat capacity compared to petrol, which essentially means 1 litre of diesel will burn you more completely than 1 litre of petrol. And to think, that all these years people in hindi movies used petrol to burn things, when diesel is cheaper and will do a much nicer job !

Add to it that 1 litre diesel is heavier than 1 litre petrol (more kg/L). While these two facts are not the end all of all reasons why the diesel engine will give more mileage in the automobile (need to consider compression ratios, fuel efficiency technologies, etc, etc) they are definitely a starting point. Essentially efficiency comparisons between diesel engine and petrol engine involves the dynamics of a mechanical system and its helpers like turbocharger, while comparisons between diesel and petrol as fuel involves chemical properties of these stuff and advances made in such areas as bio-diesel, additives, etc. And, and, and... in today's day and age, who will invite the wrath of the other perfectly normal person when it comes to environment issues. Better keep that in mind. So while petrol takes more refining from crude to be obtained, while in itself is a polluting process, diesel does not take much refraction but gives out more polluting substances such as sulfur when burnt. But then again, it seems to be compensated by its efficiency in burning as well as more mileage. Am I confused??

The articles from wikipedia:
Power and Fuel Economy of Diesel Engine
Petroleum Diesel