Life of a Huge Star v/s a Smaller Star

The Problem:

It has been found both theoretically and observationally that in comparison to smaller stars the bigger more massive ones die out earlier. Analgously it is like if two cars of same make A and B have fuels such as A has 10 liter of petrol and B has 50 liters then common sense tells us that B will go longer than A in distance but in case of stars it is exactly the opposite, which means that A will survive longer than B if A is less massive than B. The question is HOW and WHY?
So let us see logically how.

The Solution:

Let us first understand that when a star is born it is almost completely made up of  Hydrogen which sets off a fusion reaction to produce heat, light and huge outward pressure. This huge outward pressure is countered by the gravitational force inward. This gravitational force is responsible for the starting of the fusion reaction at the first place and then maintaining it.
Now let us assume two stars A and B. A starts with 100 units of Hydrogen and B with 100000 units. Automatically their masses differ by 1000 times with B being more massive. This means that the gravitational pull of A will be 1000 (approx) times less than B and hence when the respective fusion reactions begin A will burn much, much slower than B.
In a reverse way we can say that since B has a gigantic mass its gravitational force will also be massive and so will be the outward pressure due to reaction. More fuel will have to  burnt more rapidly to counter the inner gravitational pull and to keep the star stable. So that will lead to a rapid usage of fuel leading to a smaller life span in comparison to the smaller star.