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Old 05-09-2012, 10:42 AM   #1 (permalink)
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same rpm neutral vs drive

I have tried searching but I cant seem to find the simple answer. I know if i had a scanguage I would know the answer... but anyway, Is fuel consumption the same if the rpm is the same? When i am in D (OD) my van is at idle to do 50kph if i put it in neutral the rpm doesn't sound like it drops any... is there any advantage to putting the van into neutral?

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Old 05-09-2012, 11:22 AM   #2 (permalink)
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Same rpm does not equate same load.
neutral = minimum engine load.
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Old 05-09-2012, 11:37 AM   #3 (permalink)
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It will consume more fuel than 'idle'
I drove a ford taurus that did not drop the rpm when in neutral at speed.
My Infiniti Q45 drops the rpm to 600 when in neutral. Which is the same as at idle.
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Old 05-09-2012, 12:13 PM   #4 (permalink)
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I recall seeing a test done by one of the users: putting along at neutral in 1st or 2nd gear vs pulsing and coasting (engine in idle) with the average speed. The result was higher fuel consumption when idling in gear.
I can't find the actual post, sorry.
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Old 05-09-2012, 01:00 PM   #5 (permalink)
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My TDI halves fuel consumption in neutral vs. drive. From 0.2GPH to 0.1GPH, per scangauge.
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I'm not coasting, I'm shifting slowly.
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Old 05-09-2012, 01:00 PM   #6 (permalink)
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actually, it depends.

on level ground, wether rolling or stopped, you are under load, therefore, to maintain X rpm, you need to add more fuel. if you are coasting down hill, it is possible that being in gear actually lessens the load because the transmission is pulling the engine, rather than visa versa. In this case, the engine may actually go into DFCO and not burn any.
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Old 05-10-2012, 09:51 AM   #7 (permalink)
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thanks sound like i should figure out how to adjust my idle speed lower for more coasting benefit.
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Old 05-10-2012, 09:52 AM   #8 (permalink)
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OBD cars won't let you adjust idle RPM unless you reprogram ECU.
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Old 05-10-2012, 10:00 AM   #9 (permalink)
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Quote:
Originally Posted by jeongyun View Post
OBD cars won't let you adjust idle RPM unless you reprogram ECU.
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Old 05-10-2012, 03:47 PM   #10 (permalink)
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I noticed the same thing with my car when Traveling slow in 5th gear, it had me contemplating if it was useless to put in it in neutral.
Sometimes even when you give it more gas the rpm does not change but more fuel is being used, for example ,when you hit a grade and give it more pedal to compensate for the drop in rpm. This is similar to idling in neutral then putting it in gear,or so I have deduced. Your car will add fuel to keep it at the minimum rpm

Somehow it still confuses me ? I may have it wrong yet..

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