It's not self evident because it isn't true. Myths keep being perpetuated. There are repeated posts, but they get ignored. I'll try to summarize.
1. Startup as defined by automotive engineers, is the time it takes for your engine to reach EQUILIBRIUM temperature. Temperature. This takes about 20 minutes.
2. The wear that occurs during startup is caused by acid etching. The byproducts of combustion are H20 and CO2, and they combine to form carbonic acid (there's also sulfur, which can be in old oil). When your engine is cold, this stuff condenses inside it like water on the outside of a cold beer bottle. That's the cause of engine wear (during startup).
3. If you want to reduce engine wear, don't sit there idling after you start your car up. Start driving. Get some heat into the engine. Engine oil temperature is a better indicator of equilibrium temperature than water temperature. Equilibrium temperature is reached when the last part of the engine stops getting any warmer.
4. That being said, don't run such a thick oil that your oil pickup is starved or the oil doesn't drain back to the pan.
5. Of course, stay within the manufacturer's recommendations unless you're racing or something extreme.
6. The higher HTHS oils should be more protective of an engine's bearings. My engines won't see an HTHS oil under 3.5. If I were going racing, I think I'd use a minimum of 4.5 or so.
1. Startup as defined by automotive engineers, is the time it takes for your engine to reach EQUILIBRIUM temperature. Temperature. This takes about 20 minutes.
2. The wear that occurs during startup is caused by acid etching. The byproducts of combustion are H20 and CO2, and they combine to form carbonic acid (there's also sulfur, which can be in old oil). When your engine is cold, this stuff condenses inside it like water on the outside of a cold beer bottle. That's the cause of engine wear (during startup).
3. If you want to reduce engine wear, don't sit there idling after you start your car up. Start driving. Get some heat into the engine. Engine oil temperature is a better indicator of equilibrium temperature than water temperature. Equilibrium temperature is reached when the last part of the engine stops getting any warmer.
4. That being said, don't run such a thick oil that your oil pickup is starved or the oil doesn't drain back to the pan.
5. Of course, stay within the manufacturer's recommendations unless you're racing or something extreme.
6. The higher HTHS oils should be more protective of an engine's bearings. My engines won't see an HTHS oil under 3.5. If I were going racing, I think I'd use a minimum of 4.5 or so.
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