Well, I suspect (but don't know, nor without some investigation would I 
be able to calculate) that at 45 mph (the speed referenced), there would 
be little to gain by drafting, and little lost in the way of cooling 
efficiency.  If one is on a hill steep enough and long enough to require 
dropping the speed to 45 mph (I've had to go lower on occasion), the 
stock vanagon is likely to get hot, anyway, with or without a semi 
running interference.  How many list members are able to climb a 6% 
grade for several miles without resting to cool off?

On Wed, Aug 26, 2009 at 3:17 PM , Marc Perdue wrote:

> Given that drafting is dangerous, given that Mike S. probably wasn't
> implying drafting, the question remains, does drafting affect the
> cooling system significantly on a water-cooled vehicle?  Additional
> question, assuming you are not drafting but following at a safe
> distance (3 second rule), would you be outside of the lower pressure
> zone behind the truck in front of you?  Just curious...
>
> Marc
>
>
> On Wed, Aug 26, 2009 at 3:50 PM, Dave Mcneely wrote:
>> On Wed, Aug 26, 2009 at 1:59 PM , Greg Potts wrote:
>>
>>> Hi Marc,
>>>
>>> The benefit of "drafting" is the reduction in relative wind speed
>>> lessens the load on the engine.
>>>
>> Surely the poster who said he just settled in behind a semi on hills
>> wasn't talking about the practice of "drafting" (following very 
>> closely
>> behind another vehicle so as to avoid air resistance).  Of course,
>> because the vehicle ahead might make unexpected maneuvers, this is
>> extremely dangerous.  I think the poster simply meant that he follows
>> behind the semi at whatever the semi is running and at a prudent
>> distance.
>>