[T3] MPGs??

Jim Adney jadney at vwtype3.org
Fri Jul 25 15:21:23 PDT 2014


On 25 Jul 2014 at 7:47, Dennis Stiefel wrote:

> I usually just drive the car around town so on a typical day she hardly gets
> over 55.  Sounds like I need to check the MPGs under these conditions.  I
> average 70 on those trips because on certain stretches of the interstate I
> was on if you don't drive at least that fast you could get run over.  When
> my father drove it to work back in the 70s with the stock set up he said he
> got about 28 but that was 2 lane high way where the speed limit was no
> higher than 55.  I talked to some people who had a 70 notch this pasted
> weekend.  It had an automatic with some kind of duel carb set up and claimed
> 31 MPGs but they did say they averaged 65 to 60 on their speed.  Still 31
> sounded a little high to me but I guess not imposable.      

The mileage you get with any given car is strongly dependent on 
speed. You'll get your best mileage in your top gear at a speed 
that's just high enough to make the engine "comfortable." In our 
cars, that's something around 45 or so.

As your speed increases, the wind drag increases roughly with the 
SQUARE of your velocity, so your gas mileage will drop stunningly 
quickly as your speed goes up.

We get in trouble when we start to compare older Type 3s with later 
ones, since there's an unfortunate tradeoff between NOX emissions and 
gas mileage. The FI cars were designed to meet the emission 
requirements that started in '67 and got tighter every year after 
that. So under the same driving conditions, a '66 will always pollute 
more and get better gas mileage than a '72.

I did some test drives a few years ago, with my FI '71 and got ~26 
mi/gal at 65 mi/hr and ~29 mi/gal at 60 mi/hr. Those are the best 
numbers you should ever expect to see in your '72, unless you've got 
a tail wind. The earlier cars, with OE carbs, get significantly 
better mi/gal, but pollute significantly more.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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