Re: Fuel Usage When Idling

David turned on the Etch-A-Sketch and wrote:


>>Your 6.0 Vortec will use slightly less fuel at idle than your 6.6 L
>>Duramax, obviously.
> 
> You've never seen someone drive two vehicles at once?  Its astounding!

Need to watch bullit again...


> 
> I know the Duramax has a larger displacement, but I thought the
> Duramax would have less fuel usage at idle because its a diesel & the
> Vortec is a gas engine.  The Duramax does get nearly twice the
> miles/gallon that the Vortec does under similar conditions when being
> driven.


Having done a ton of research on diesels - and wanting a duramax (or even
the future mini-duramax 4.5L) in my Avalanche - I know that the difference
comes from a few factors.  (I'm seriously considering buying a used
Mercedes 300d or 300sd for commuting purposes.)

First, diesel fuel has more energy per volume than does gas. (At least it
did before ULSD fuel.)  Therefore you need less of it to create the same
amount of torque to push your cylinders up and down. 

Second, because the torque curve is lower, you need less RPMs to move the
vehicle forward than you would with gas.  

However, at idle, I don't know if there is any difference.


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