Idle

[Sludgy]

The new Scangage is awesome! One thing that is immediately noticeable is the difference between idle fuel rate when the truck is in gear or in neutral and cold or warm.

When cold, the engine idles at 1.2 gph in gear. It drops to 0.9 in neutral.

When warm (the 6.0 liter diesel/cast iron engine takes FOREVER to warm up) it uses 0.6 gph in gear and 0.4 gph in neutral.

Now I regularly put the truck in neutral at stop lights. This should have a significant impact, since my commute is stop-and-go.

And I'm thinking of an engine block heater.

And my next truck will have a manual tranny.

[philmcneal]

nice job, at least truckers can conserve too! Sometimes I like following big old trucks because they always try to time the red light to green, so they go slow for a reason.

If I had a CVT then I'll trail behind them more often, but with a man tran I'm usually in 2nd or 3rd when following them and that's a big FE killer ;(

With a manual tranny you can shut off the engine at will (when you don't need it) and turn it on half a second earlier when you need it via clutch.

Enjoy your new toy, I'll be getting mine soon enough!

[SVOboy]

I wonder why you're using less gas in neutral with the auto. At least for my auto when it's cold it'll be at 2k rpms in neutral and then only like 1k in gear. Hmm.

[diamondlarry]

Originally Posted by SVOboy

I wonder why you're using less gas in neutral with the auto. At least for my auto when it's cold it'll be at 2k rpms in neutral and then only like 1k in gear. Hmm.

I think it's because of the load that's placed on the engine. If there's enough of a load to drop the rpm's from 2K down to 1K that's fairly significant.

[SVOboy]

Hmm, I wonder, I've never really put all that much thought into it.

[MetroMPG]

since initially doing the idle warm-up experiment, i kicked myself for not recording the fuel consumption data in the few first minutes.

sludgy's post today about his idle gallon-per-hour observations inspired & reminded me to complete the test.

(full details in the original warm-up experiment thread).

the finished chart:

<img src="http://metrompg.com/offsite/warm-up-chart-complete.gif">

[Compaq888]

wait let me get this straight...
If I'm driving and I come up to my light and put it in neutral instead of keeping it in Drive I'll actually gain mpg??????

[Bunger]

Ya, the torque converter (basically 2 fans suspended in trans fluid, one connected to the engine, the other to the trans) is what allows you to stay in gear even with the engine idling. But it takes more power to do so. So I can totally see why you would increase mileage by puting it in 'N' when at a light.

[Matt Timion]

This is really an awesome thread. It is showing very simple things to do to increase fuel economy. These are things I would have never thought of as I havn't owned an automatic car in a while.

I wish there was a cheaper obd2 data tool out there. I think everyone that can afford it should have a scangauge. Just watching your MPG rise by doing simple things like putting your car in N must be amazing.

[Compaq888]

Thanks, I was about to give up on my car. I actually went 4000rpm today because I was tired of not finding some way to control my fuel injection.

And thanks to Matt too. If it wasn't for this website I'd still be at 24mpg mixed driving. Now I'm at 28.