Imagine two starts are exactly the same size, but one of the stars to greater mass than the other. which star will burn out all of its fuel first

The larger star will burn out faster. as nuclear fuel is burned out due to higher percentage being consumed.

Explanation:

Gravity on the other hand is only affected a little during this process and mass use. Solar mass loss is caused by mass that is turned into energy (E=mc²), but also by the material that is lost to the solar wind.