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I don't doubt that the expert consulted for this article knows way more about gasoline engines than I do, but the article itself contains some flat-out falsehoo

I don't doubt that the expert consulted for this article knows way more about gasoline engines than I do, but the article itself contains some flat-out falsehoods. In particular the line "But don't confuse warm air coming from your car's radiator with a warm engine." is just wrong. The engine temperature sensor actually senses the engine coolant temperature, and if your dash is blowing warm air, then the coolant is way warmer than 40F,and the engine has leaned the fuel mixture. I also wish the expert had addressed the real question in this warming scenario - which is how many piston cycles (crankshaft revolutions) you run with an over-rich fuel mixture. It's certainly true that engine warm-up takes longer at low rpms, but it also true that if you run at driving rpms, while the elapsed time to end the over-rich fuel will be less, you will have cycled the pistons many times more than at an idle. It's the piston movement he's tagging as the engine wear culprit, and it's not at all clear how many more piston cycles there really are, if you warm at an idle. It's not even clear there are more, thinking from first principles.

iroddis 4y ago
Many new cars have electric heaters for the air venting into the cabin. In that case their statement about confusing warm air with a warm engine would be true.
- jnsaff2 4y ago
  Especially small diesels which take too long to warm up for passenger comfort.
  - walnutclosefarm 4y ago
    Yes, but the whole argument about washsing the oil off cylinder walls is irrelevant to diesels, as excess diesel lubricates, rather than dries cylinder walls.
- walnutclosefarm 4y ago
  Could be. I've never encountered one, and I think they would be a dead loser where I live. In fact, the thing I dislike most about our electric vehicle is that it's heaters are so wimpy. Probably wouldn't matter if I lived South of the Mason-Dixon line, but at -20F, they are awful.
hermitdev 4y ago
ICEs will also use recycled exhaust to warm intake air. There's a separate sensor for intake air temp and I think a separate oxygen sensor that should inform the fuel mix. At least in my performance car, there are separate gauges for engine oil, transmission fluid, coolant and air intake temperatures. Those are all exposed to me in dash. I think traditionally, the only temperature exposed to the driver is the coolant temperature as that's usually the only one that really causes problems with overheating.
- walnutclosefarm 4y ago
  I am not current by any means with many makes of contemporary cars, but those I have had anything to do with used the coolant temperature sensor as the input to the fuel adjustment. I'm not saying that's universal, but it certainly is common, and makes a lot of sense if you're looking for a reading on the engine operating temperature, since that's what the coolant regulates.

iroddis 4y ago

Many new cars have electric heaters for the air venting into the cabin. In that case their statement about confusing warm air with a warm engine would be true.

jnsaff2 4y ago
Especially small diesels which take too long to warm up for passenger comfort.
- walnutclosefarm 4y ago
  Yes, but the whole argument about washsing the oil off cylinder walls is irrelevant to diesels, as excess diesel lubricates, rather than dries cylinder walls.
walnutclosefarm 4y ago
Could be. I've never encountered one, and I think they would be a dead loser where I live. In fact, the thing I dislike most about our electric vehicle is that it's heaters are so wimpy. Probably wouldn't matter if I lived South of the Mason-Dixon line, but at -20F, they are awful.

hermitdev 4y ago

ICEs will also use recycled exhaust to warm intake air. There's a separate sensor for intake air temp and I think a separate oxygen sensor that should inform the fuel mix. At least in my performance car, there are separate gauges for engine oil, transmission fluid, coolant and air intake temperatures. Those are all exposed to me in dash. I think traditionally, the only temperature exposed to the driver is the coolant temperature as that's usually the only one that really causes problems with overheating.

walnutclosefarm 4y ago
I am not current by any means with many makes of contemporary cars, but those I have had anything to do with used the coolant temperature sensor as the input to the fuel adjustment. I'm not saying that's universal, but it certainly is common, and makes a lot of sense if you're looking for a reading on the engine operating temperature, since that's what the coolant regulates.