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I was reading this question about regularly turning the engine off by dropping the clutch in first gear. This is fairly obviously a bad practice, and the answers give great reasons why, but it got me thinking: are there any adverse effects to turning the engine off with the transmission in neutral and the clutch engaged vs with the transmission in neutral (or in gear) and the clutch disengaged (pedal to the floor)?

I was thinking that with the clutch engaged + tranny in neutral, you're still having to spin down the extra weight of the clutch & input shaft of the transmission, which would slow the engine down more quickly; whereas with the clutch disengaged, the weight needing to spin to a stop would end with the flywheel/pressure plate/TO bearing.

Would leaving the clutch and tranny input shaft 'attached' be enough extra drag to cause even the slightest wear on any part of the drivetrain? This is all assuming the vehicle has come to a complete stop.

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It's actually a trade off between what would get worn and what wouldn't ... but with that said, the wear in either case would be infinitesimal.

Since you stated "... enough extra drag to cause even the slightest wear ..." ... the rotating parts of the transmission will be worn, but no more than any other time it would be spinning freely without any sort of pressure or torque applied through it. The trade off is you'd have an extra little bit of wear on the throwout bearing. Again, this would be infinitesimal. So small it probably couldn't even be measured.

I don't think there is one way or the other which is better. Neither way is going to cause any harm to any part of the transmission or engine.

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