Fuel Usage When Idling

Cheers

Are you driving them both at teh same time?

(sorry, couldn't resist!)

I've seen information out there - but I forget where - that calculates the fuel consumption at x RPM for a given sized engine.

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!

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.

Need to watch bullit again...

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.

I have not noticed a significant drop in mpg since ULSD fuel appeared on the market.

I don't know for sure what idle fuel usage is. I have heard rumors that Class 8 trucks (big over the road rigs) will burn a couple of gallons idling overnight. I have no idea if this is true or not.

The original reason for my post was to find out if there are any reasearch studies, surveys, etc. that document idling fuel usage. This information might come from the feds, from vehicle manufacturers, private individuals, etc.

I would like to know if anyone has any verifiable idling uysage info or knows where I might find it?

I have Cummins and have had a Cat. The small "B" series (5.9l) Cummins and the Cat 3126 (7.2l) each used around 3 gallons per night of idling, confirmed by evening and morning fillups. Diesels idle at about an 80:1 air/fuel ratio. Gas engines 12:1? I did idle a 350 Chevy van overnight and noticed the gauge dropped from 1/4 tank to below empty, never tried that again.