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Comment by Lanolderen | Hacker News Reader

New engines are however made en masse out of alu which expands more than iron/steel. The argument that driving reduces wear makes little sense to me since whatever you do outside of sitting in neutral (fast idling if need be/not already programmed into the ECU) is increasing stress on the components that are not (optimally) lubricated and at a tighter than optimal clearance. Then again manufacturers know people can't even wait 30 seconds so engines are designed with that stress in mind so it's not the end of the world.

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Engines are lubricated almost immediately. The oil pump is typically camshaft driven, so it's only a matter of seconds before everything is lubricated. In addition, modern oils tend to "stick" to parts better and don't drain off as easily. It takes quite some time before they're completely dry.

As far as the material, at one time engines had components of various materials. Blocks of cast iron, heads or intake of aluminum. Now as you state, they are mostly aluminum. While it may expand more than steel, the majority of the components are going to expand at the same rate, unlike in the past.

Oils are definitely better but I really don't believe the marketing in winter. At low temperatures even modern oil has high viscosity. Combined with tight bearing clearances I firmly believe in waiting a bit to be sure everything is nicely coated. Maybe I'm just paranoid from horror stories of dudes getting on their bikes and ragging them right off the bat, seizing the engine.

I mentioned the aluminium mainly because piston slap came to mind. More slop, more slap. It's better than everything twisting though.

I use full synthetic engine oil for cold weather startability, primarily.

Most of the car manuals for the last few cars I've owned (VW Passat, Kia Rio) all state to avoid excessive idling in general. Cylinder wash from unburnt gas at idle as the car warms up being the main culprit in engine damage. It rarely gets below 20F or so here so at most I start the car and give it a few seconds to get oil moving and once I see the revs come down its careful sub 2.5K rpm driving as the car warms up.

Weren't the excessive idling warning introduced as an emissions thing? Correct me if I'm wrong. Just did a little search and found a nice compilation of user manual info regarding startup procedure [1] and they all pretty much go on about wasted fuel.

[1]https://info.ornl.gov/sites/publications/files/pub61263.pdf

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