why having short trips with a car are worse for the engine than the long ones?

Question

Often people explain that it’s because you ride a cold engine. But a long ride also starts with a cold engine. So how can two 5km trips per day be worse than a two 20km trips per day if an engine starts cold in both scenarios?

Or does this arguments works under presumtion that you ride 100km in 20 short trips vs 5 trips?

In: Engineering

Answer 1

Think of it as engine hot/cold cycles. It is better to drive 100 miles on one hot/cold cycle than 100miles on 5 hot/cold cycles.