Skipping oil changes allows your engine oil to break down and fill with dirt, metal shavings, and other contaminants. Over time, this dirty, worn-out oil cannot properly lubricate engine parts, increasing friction and heat inside the engine. That extra stress can lead to faster wear of critical components, reduced fuel economy, and possible overheating. In extreme cases, sludge can form, oil passages can clog, and the engine can seize or fail completely, which usually requires a very expensive repair or engine replacement. Missing one oil change usually will not destroy your engine, but repeatedly delaying or ignoring oil changes can cause serious, permanent damage.