A proper language comparison...

[Walter Bright]

On 7/26/2013 4:07 PM, Andrei Alexandrescu wrote:
> On 7/26/13 3:52 PM, Walter Bright wrote:
>> Although commonplace, it is poor practice to use the engine to slow the
>> car down (unless you're dealing with brake fade from overheating).
>
> I know next to nothing about cars so take this destruction with a grain of salt.
>
>> 1. Brake pads are cheap compared with engine rebuilds.
>
> My understanding is that engine brake does not destroy the engine. It does not
> involve friction.

It's news to me that engines are frictionless! (The braking effect is only 
partially due to engine friction - the pumping of the air is most of it. But the 
engine WEAR is due to friction.)

> Indeed Wikipedia agrees:
> http://en.wikipedia.org/wiki/Engine_braking and even mentions "Engine braking is
> a generally accepted practice and can help save wear on friction brakes".

Of course it saves wear on the brakes. The issue is do you prefer wear on your 
engine?


>> 2. Using the engine as a brake can cause unburned gas to wash the oil
>> off of the cylinder walls, resulting in excessive wear.
>
> [citation needed]

Mechanics at the dealer told me this. They had no reason to lie to me.


>> 3. The engine is not designed to be a brake. Use the brakes. Brake pads
>> are not precious :-)
>
> Engine brake is a natural artifact of its design. I don't think you can build an
> argument around "wasn't design to do that, so don't". Engine braking is a
> widespread and common technique.

I agree it is widespread and commonplace. That's why the mechanics felt it 
necessary to tell me not to do it. I was also told not to do it when I took two 
different courses in track driving - the Bob Bondurant and Skip Barber ones.


> I use engine braking most of the time (I always drive manual so that's easy).
> Saves gas and I've never had a mechanic tell me "you better go easy with that
> engine brake, look at them cylinder walls!" My brake pads reach a state of
> immortality.

The object isn't to save brake pads, it's to reduce the wear and tear on your 
engine.