Is 10w30 thicker than 5w30 motor oil?

Yes, 10W30 motor oil is thicker than 5W30 motor oil at higher temperatures. The first number in the oil designation (the "W" stands for winter) indicates the oil's viscosity at low temperatures, meaning 5W30 is thinner in colder conditions compared to 10W30. However, both oils have the same viscosity at operating temperatures (30), meaning they perform similarly once the engine is warmed up.