<VV> Better mileage with convertible top down!!

jvhroberts at aol.com jvhroberts at aol.com
Sun Aug 21 09:54:26 EDT 2011


 There's also a 'theory' out there that cars get better gas mileage with their windows closed. Now, I'll say right up front, this is just one data point, and certainly that's no trend, but here goes...

Got this here 2005 Legacy GT wagon, stick shift. It also has an instantaneous as well as an average MPG readout. 

Drove along the same stretch of road, same outdoor temp, windows all closed, then again with the windows all open as well as the sunroof. Cruise set at 60.  I saw no change in the instantaneous MPG, and this was over several passes over a couple of weeks. 

Now, given all the 'holes' I opened up in this car, I would believe that a retracted convertible top wouldn't be any worse! 

Now, a buddy of mine with a fairly new pickup did the same test, tailgate up vs. down, and did see about a 1.4 MPG improvement with the gate down. 

Anyone have a wind tunnel in their back pocket? <G>

 

John Roberts
 

 

-----Original Message-----
From: mark <mark at noakes.com>
To: John Gull <vairdude at gmail.com>
Cc: virtualvairs <virtualvairs at corvair.org>
Sent: Sun, Aug 21, 2011 8:37 am
Subject: Re: <VV> Better mileage with convertible top down!!


John,

Convertibles are not exactly aerodynamic top up or down. Is it possible 
that with the top down that you drive more slowly? That could make more 
difference than aerodynamics at slower speeds.

I have a beater Corvette convertible. I almost always drive it more 
slowly when the top is down due to the wind turbulence in the interior 
and prefer to cruise the interstate with the top up.

Now if you're driving with the top down at 70mph and still getting 
better gas mileage...disregard my suggestion...

Mark N

On 8/21/11 6:51 AM, John Gull wrote:
> Ray and others, I am still in the testing phase but the last 3 weekends I
> have gone on 200 mile trips with the convert top down and have added 2 mpg
> to my usual average.  Maybe less drag coefficient? Why? I don't know for
> sure but I am willing to test more! Anyone else noticed this? Maybe ,then
> converts are better than coupes!  HAHA John Gull in the Blue ridge mts of NC
>

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