How does elevation affect engine performance?

As elevation increases, the density of the air decreases. This reduction in air density affects the amount of oxygen available for combustion in an engine. Since internal combustion engines rely on a precise fuel-to-air ratio to function optimally, less air means less oxygen is available to mix with the fuel. Consequently, the engine cannot produce as much power, resulting in a decrease in horsepower.

This phenomenon is particularly noticeable in carbureted engines that operate on a fixed air-fuel ratio. At higher elevations, the engine may struggle to maintain efficient combustion, leading to a loss of performance and lower horsepower output. Adjustments or modifications might be necessary to compensate for this loss in power and maintain optimal engine performance in high-elevation environments.

The other options provide incorrect interpretations of how elevation impacts engine operation. Horsepower does not increase with elevation, as the lack of sufficient air density negatively affects performance. Fuel composition does not change in a way that makes it richer in nutrients at higher elevations, nor do engines necessarily operate more efficiently in those conditions without adjustments.