> Imagine if ford started to detune your engine as you added miles to the car, but DIDNT TELL YOU. You lost X horsepower every 1,000 miles. Would you guess, th

> Imagine if ford started to detune your engine as you added miles to the car, but DIDNT TELL YOU. You lost X horsepower every 1,000 miles. Would you guess, this is actually what's happening. ECUs constantly adjusts for current conditions (EGR, variable gem turbo, o2/fuel ratio, fuel inlet timing, combustion timing, variable cam timing and phase, knock sensor...). As the engine is used, wear makes its performance degrade over time, and the ECU adjusts in real time for that. Maintenance such as timely oil change mitigate that, some parts may have to be replaced at some point (from spark plugs to turbo), and over time the engine itself wears out. Here's a very specific example: all those cars with hypermiling downsized engines turbocharged to compensate perform brilliantly, but when the turbo is dead they can barely crawl themselves in 1st gear. In less extreme situations, turbo wear will put you relatedly anywhere within that [perfect, broken] range, and the ECU will do its best to compensate, unbeknownst to you.