Tata Manza has clocked a mileage of 46.33 km per litre!!!

I feel its the other way round. Petrol has better calorific value than diesel and hence would produce more energy

you r right... petrol has more cv than anything used as fuel now...

@Sridhar/Narayan - diesel has greater energy density than petrol, which means that more energy can be extracted from a unit volume (say, litre) of diesel than petrol. Plus the higher compression ratios at which diesel engines work also add to make them more efficient than equivalently powerful petrols.

Because of the way diesel and petrol engine work, diesel are torquey and petrols are "revvy" - in other words diesel engine have load carrying capacity at low speed (whilst not being able to spin that fast) while petrol engines can be happily revved to much higher levels. However modern technology is bringing diesels closer to petrols in terms of revving while also keeping their low-end torque benefit.

i agree with energy nd density... but here issue was with calorific value..

Well not sure how calorific value comes into the picture - its not how much heat the fuel produces by burning that's important but the amount of mechanical energy that can be extracted from it by heating it to the point of burning. Do I make sense?

You do dear... diesel does produce more energy, which in terms mentioned as power.. our issue is with efficiency,..

Efficiency? If diesel produces more mechanical energy upon burning, as far as cars or mileage is concerned, is it not more efficient than petrol? What exactly is the "efficiency" being discussed here pertain to?

Hi,

I would like to mention my results of extracting highest fuel efficiency. I recently got my fuel tank issue solved.

There was little petrol in tank before complete refill. Then I filled the tank completely with 30.66 litres.

I was using the car from my home to clinic. and then back home. 90 % of road is highway. Indica's tachometer shows 4 segments between 1000 - 2000 rpm. So 1 segment is 250 rpm

I tried to maintain constant RPM of 1500, but there were incidences where I had to down shift, and many times crossed 1750 RPM speed. Speed at 1500 RPM in 5th gear was 56 kmph.

Total Distance travelled is 206.5 km.

Today I refilled the tank to maximum and fuel clock showed 12.1 litres.

So my Indica's FE is 17.07 kmpl ...... !!!

ARAI figure is 16.83 kmpl.

All Auto magazines claim tata Indica FE figure as 14.5 to 15.5 kmpl.

I am sure, on long distance travel on highway can give figure of 18.00 kmpl. never imagined that good driving condition can give FE of more than 15 for Indica.