What is the effect of high altitude on engine performance?

At high altitudes, the engine performance is notably affected due to the decrease in air density. As altitude increases, the amount of oxygen available in the atmosphere decreases, which is essential for combustion in an engine. This reduction in oxygen supply results in decreased engine power output because the engine cannot burn fuel as efficiently as it can at lower altitudes where air density is higher.

Additionally, the lower atmospheric pressure at high altitudes means that the engine is receiving less air mass, further hindering its ability to generate power. Therefore, the correct interpretation of how altitude impacts engine performance is that it leads to a decrease in power output, aligning with the understanding that higher altitudes produce less effective combustion processes within the engine.