What happened to the mileage of small petrol cars?

With My Brief usage of 1 year with diesel Indica ,I noticed that Mileage does not vary much attributed to a Higher speed You Drive in Highways.While in Petrol cars ,I experienced mileage drop above 60kmph.

That's exactly what I have said in post 9 before - though I haven't physically compared/experienced the difference.

Not all of them.  A vast majority of the diesels running in India, including the Indica diesel (not Quadrajet) are INdirect injection diesels.

Direct Injection engines would be the Skoda TurboDiesels + some Mahindra and Tata engines like those on the Major, the Sumo Di, etc and all the Common Rail engines in use today.

Diesels dont catch fire more easily than petrol, but diesels are combustible under pressure while petrols require a spark.  Because petrols require a spark, the TIMING of the spark is very important for efficiency.

OK,

I should have simply said said "injection". even the ones termd as INdirect injection are broadly put uder direct injection engines only as the fuel is injected inside the cylinder under high pressure.

The fact that deisel catches fire at high pressure while petrol doe not is also due to the fact that deisel catches fire more easily as compared to petrol. Even in the Direct Injection petrol engines, the major challenge was to create such a high pressure where petrol too could catch fire. This has now been acheived and pretty soon we will such engines being mass produced and form a part of every petrol car across the world.

Direct Injection diesels are different from indirect injection diesels which use a PC (Pre Chamber or Pre-Combustion Chamber) and the fuel is not injected directly into the cylinder.

DI engines are noisier than IDI/PCI engines, but DI engines are more fuel-efficient and have better low-end and max torque.

You may refer to this Wiki page for more info:

http://en.wikipedia.org/wiki/Indirect_injection 

Hi Nikhil...

Basically there are  two types of engines in alto. one is 1000cc  Engine(now it is not available in market) another one 800cc engine. Which one you owned?

Then we should just wait for direct fuel injection cars - petrol version - if the car manufacturers have thought about it.

I am still a little surprised about the point of mileage dropping beyond a certain speed in petrol cars. I haven't measured this, but when I am driving more in 5th gear (at speeds of 50 kph and above), I save on fuel. The fuel lasts longer. Will check this out when I refuel this time.

The mileage is defintely better on highway - in case of petrol & diesel, both.  The point is that increased load/power affects mileage of petrol cars more than diesel cars.

Really?

In fact, diesel has low flammability - reducing the risk of fire.