[Mgs] Overdrive Numbers

[Aaron Whiteman]

On Jan 15, 2008, at 2:32 PM, Charles & Peggy Robinson wrote:

>    Tell John Twist.  He thinks overdrives are strictly "feel good"  
> add-ons.

That corresponds to my anecdotal experience.

Dads 1978 MGB got 28-31 MPG @ 70 mph on extended trips.  It had no  
overdrive and ran all day at 4000 rpm (or more, I don't remember the  
exact figure).

My 1975 MGB gets 26-30 MPG on the same trips.  It has overdrive and  
runs at say 3500 rpm.

The '78 had a 25D distributor and a downdraft weber and was recently  
rebuilt (less than 20K miles).  The '75 has a 45D with pertronix and  
dual SUs, but is pretty tired.  I need to get over and buy dad's car,  
if only for the engine.

My experience says the OD doesn't matter one bit regarding mileage,  
but when my OD broke and would not engage, it was disquieting for me  
to listen to the engine at the higher revs--even though I knew it was  
just fine.

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