What will happen when petrol is used in diesel engine?

Answer 1

The car won't go faster, in fact it will not run at all!

Diesel is classified using the Cetane scale (15 to 100, not 0 to 100) where Cetane has been given the number 100. A diesel fuel is supposed to self ignite easily and this is measured in a standardised test using a variable compression engine. A Diesel engine uses the heat from the high compression pressure to ignite the air-fuel mixture (no spark plugs!). Cetane number = measurement from the point of injection until ignition (iqnition quality). General cetane values vary from 40-55.

Gasoline is classified using the octane scale (0 to 100) where octane has been given the number 100. This sort of fuel should have a high value on the octane scale if it is to be used in a spark ignition engine. General octane values vary from 90-99. Please note that there are different test procedures when determining the Octane number, RON and MON + others. Please note that that Octane had the best know anti-knock properties when the first certification took place and that for instance ethanol, methanol etc have better anti-knock properties.

If the fuel used in a spark ignition engine has too low octane number it might just have a tendency to knock (uncontrolled combustion, ignition pre-flame front) which produces a high frequency noise (can lead to engine failure).

If the fuel used in a compression ignition engine (ie Diesel engine) is a high value octane fuel it is very resistant against auto-ignition and will most likely not ignite. If the gasoline ignites at all it is not likely that it will do so at the right time.

The diesel fuel works as a lubricant for the fuel-injector(s)/pump so if gasoline is used this can lead to injector/fuel pump failure (over time).

As a rule of thumb: Octane number = 120 - 2 * Cetane number

and vice versa.

To sum up:

Gasoline:

Low boiling point, high self-ignition temperature, bad lubrication properties

Diesel:

The opposite