Just one more plug to add to this.
Does the reduced RPM save wear and tear on the engine? Probably. Is it
measurable? Probably not in any significant manner at normal driving
speeds, but at 85 - 100 MPH, yes.
Does it increase gas mileage? Probably. Is it measurable? Well in my past
experience it may give an extra 1 mpg at freeway cruising speeds with the
wind in the right direction if going down hill etc..... Is it worth it?
YES every da*m dime. Just the reduction in engine noise while cruising down
the interstate at 70 is worth it. The car may not feel any better, but I
sure do.
I think the real savings on the mechanicals is probably at the higher engine
rpms when cruising at speeds in excess of the posted limits (85 +). When
you start to get over 80% of the rated maximum rpm, its bound to take its
toll. If you're talking about driving around town, then the overdrive
should probably never need to be engaged.
All of this of course is JMHO, and YMMV.
H.
-----Original Message-----
From: Neil Cotty <neilc@tradesrv.com.au>
To: mgs@autox.team.net <mgs@autox.team.net>
Date: Monday, February 22, 1999 7:53 PM
Subject: Re: MGB Overdrive??
>Hi all,
>
>>IMHO, not quite, drive your car at ALL speeds in 4th gear and see how long
>the
>
>
>Obviously if you use the Overdrive at all speeds in 4th gear you are
causing
>additional wear to the engine as you are lugging the thing, it's like being
>in 3rd when you should be in 2nd etc. There is a range where the motor is
>comfortable pulling lower rpms to achieve the same MPH, outside of this an
>Overdrive is practically useless, BMW states this fact in their Owners
>manual. It's how you use it, thats the important thing. The statement I
took
>issue with relates to Freeway conditions (constant speed). If you are doing
>75mph on a freeway lets say for 500 miles, and you are in a car with
>Overdrive vs a Car without. I am saying that the car with Overdrive will
>achieve better Fuel Economy and result in less wear in the engine. It
>doesn't matter how miniscule the less wear or less fuel consumption, if
>there is lower RPMs and the engine is working easily to propel the vehicle
>and is not lugging, you will be saving wear and tear on the motor and
>achieving better MPG.
>
>Why on earth would Car manufacturers around the world make these things if
>this was not the case? They wouldn't waste their money developing the
>things. An Overdrive, *properly* used (key thing here), must save $ at the
>pump and result in less Engine wear - even a teensy amount less wear is
>still an amount, and over x thousand miles that must add up.
>
>Now if I ever get my blasted O/D working again... <VBG>
>
>Cheers,
>Neil.
>
>
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