[pillay]

pillay asked the Naked Scientists:
I love the naked scientists show! I download your podcasts.

I want to know the difference between a car running on diesel and a car running on petrol. Are they the same?

What do you think?

[graham.d]

The fundamental difference is that a petrol engine compresses the fuel-air mix and then it is ignited by a suitably timed spark, whereas a diesel engine compresses much more and it is the compression itself that ignites the mixture. There are many important factors that are used to optimise each engine type and factors in the fuel that control its rate of burn but that is the principle. The engines have slightly different characteristics as a result, but these difference are not so noticable in the latest cars because of gearing and use of turbo-charging.