In a car that has a trip computer that tracks MPG, it's fun to see how far one can stretch a tank of fuel. One of the Hyper-Miler tricks is to coast down long grades in neutral (a no-brainer with a manual transmission.) However...

...that appears to be tortuous to the Merc W5A580 tranny in the 4.0L XKR. Would someone be willing to explain just what happens when the car coasts in neutral an how that damages the transmission.

I'm always happier to not do whatever I'm not supposed to do when I understand WHY.

 

Coasting in Neutral or Gear to Save Gas - Coasting and Fuel Economy

Not saying it's bad, but you're not saving gas. The engine computer can (does/should?) Turn off gas at the injectors while load approaches zero. Engine keeps turning over from wheel driveshaft rotation. Put her in neutral and engine goes into idle mode, injectors fire, uses more gas.

I couldn't find anything that says you'll damage the tranny in neutral, let's see what others think. I guess anyone would have to admit safety takes a hit without the ability for on demand accelerating. I've seen claims that a car will handle better in drive than neutral, guess if you think about it we all use weight shift via accelerator to improve performance so that too makes sense
John

 

Roger, almost forgot one "fun" fact. It's illegal to do so in your state of Texas. [Like they'd ever know, right ��]

John

 

I wonder if that's because we have so many mountains...? But my car is actually originally from your state, so I could just say it didn't know.