Does leaving a manual transmission car in gear (tip:lowest ratio gear offers the greatest resistance due to engine compression) present any disadvantage to the mechanicals of a vehicle? Parking brake has numerous disadvantages to leave it on, especially during wintertime, so it is out of the question if it's good practice. (this part is to avoid being flagged as duplicate again...) Please take into consideration all the factors such as, the drive of the car (fwd,rwd or awd), distribution of masses, or for example if the car is parked on a steep incline, be it facing forward or backwards.

  • not in a million years :) – Flaviu Suciu Nov 24 '16 at 15:36
  • Compression is not the reason. The cylinders are not absolutely air tight, and the vehicle would creep slowly when the compressed air escapes. It's just friction! – sweber Nov 24 '16 at 23:44
  • @sweber, try pulling the spark plugs or injectors on a diesel and you'll see that there really isn't all that much friction. What enables a stopped engine to hold on a hill is the work it takes to compress the air in the cylinder that is on the compression stroke. – dlu Nov 25 '16 at 4:37
  • @dlu it is true that most of the torque needed to crank a motor is to overcome compression. Apply a too-low-to-crank torque, and the pressure holds the car. But over time (hours? days?), the air vanishes and the motor moves a little. – sweber Nov 25 '16 at 8:18
  • i don't understand why you people would flag it a duplicate when it obviously is another question... god damn internet experts :) – Flaviu Suciu Nov 25 '16 at 8:43

No, it puts some stress on the transmission/driveline, but not much. It's negligible compared to the stress it gets when you drive the car, even when parked on a steep hill. You must have driven up the hill to come there in the first place, so it also won't hurt to stand still on it while in gear. It is often done to prevent a frozen handbrake during winters, as you said. Most of the times the reverse gear is the one with the most resistance.

  • Indeed, because of the ratio being smaller than 1'st gear, but on some cars it is not handy to put in reverse because of buttons and position of the gear, that's why i mentioned 1st – Flaviu Suciu Nov 24 '16 at 16:19

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