Traveling at high altitudes vehicle engine performance when compared to operating the same vehicle at sea level

Lessens

Explanation:

The performance of an engine at high altitudes is lower due to the decreasing density of air with elevation, such that at high altitude, the density is much less and a given quantity of oxygen occupies much more space at high altitudes, and the oxygen content in the air drawn in is lesser at high altitude, and the combustion power is much lesser at high altitudes when the engine speed is high up to about 4000 rpm.