> 
>    When you crest many of our western US passes there are signs warning of
> downhills, and notifying you..."Use Lower Gears."......the problem is that
> many don't pay much attention to those...until they start to feel their
> brakes losing power due to overheating...and THEN they try to fix the
> situation....
> 
Signs warning of downhills and the need to gear down are quite common in Eastern Canada too.

> 
> Date:    Sat, 14 Sep 2013 10:55:35 -0700
> From:    Ben <syncro@GMAIL.COM>
> Subject: Re: Why Bigger Brakes Was Cause of brake rotor warping
> 
> On Sep 14, 2013, at 8:37 AM, Don Hanson <dhanson928@GMAIL.COM> wrote:
> 
> > That is why we encounter very slow trucks on the downhills
> > as well as the climbs....They've shifted to a low enough to hold their
> > trucks from gaining speed...and thereby they can control the heat they
> > create with their brakes.....
> 
> 
> If this statement is about very large trucks such as diesel rigs, this would=
>  be less than an accurate statement. Excerpt taken for Wikipedia which is ac=
> curate enough for this discussion.
> 
> "Diesel engines do not have engine braking in the above sense. Unlike petrol=
>  (gasoline) engines, diesel engines vary fuel flow to control power rather t=
> han throttling air intake and maintaining a constant fuel ratio as petrol en=
> gines do. As they do not maintain a throttle vacuum, they are not subjected t=
> o the same engine braking effects."
> 
> So, NO. Those trucks are not downshifting to slow down. They are using alter=
> native mechanisms such as jake brakes. Ever notice that the diesel in your V=
> anagon & other VW's have an auxiliary pump to create vacuum for your brake b=
> ooster? Same deal.=20
> 
> 
> 
> BenT
>

Read the rest of the Wikipedia article before suggesting that 'NO. Those trucks are not 
downshifting to slow down'.  Later in the article, it makes it clear that turbo-charged 
diesel engines do have engine braking, thanks to the turbocharger.  Certainly every 
turbocharged diesel VW I've driven has had engine braking - not as effective as a gas 
engine of the same size, perhaps, but more than enough to provide good engine braking 
grades.  The 'jake brake' on the big guys also works best if you gear down, I understand.

James
Ottawa