No.

Clutching in and putting it in neutral would let the rpms fall further than if you left it in gear.

It's a hypermiling technique. You don't leave the car in gear unless the clutch is in for the gas savings your speaking of.

 

http://ecomodder.com/forum/showthread.php/...ation-3543.html

 

http://ecomodder.com/forum/showthread.php/...sting-3050.html

I guess if you were talking about trying to coast to a stop.

But hardcore hypermilers would turn off their engine completely....

 

Thanks for the answers guys. Its good to hear that I'm not the only one experiencing this. Also like hansai00 my car also jerks forward sometimes under low rpms when decelerating, but then i guess this is normal too. I'll breathe easier knowing that I dont have to replace anything now.

 

Yeah, I agree with CKit. I don't know what thomsbrain is trying to say by keeping it in gear to save gas, that's absurd. Just pop it into neutral when coasting for that..

 

They're both right. I didn't read ckit's articles but I think he came to the same conclusion in the end anyway.

If you're coasting to a stop, and you leave it in gear, your momentum keeps the engine spinning. The ecu won't need fuel to keep the rpm's going to avoid a stall, hence mileage goes through the roof during coasting. You'll get this effect the best when coasting downhill in gear. You get a similar but short-lived effect coasting on a flat surface. I suspect this is why the op could get it to coast all the way down to 1k (I've never tried that). His momentum is keeping the engine spinning.

In other cars, you could leave it in gear, and not apply gas, and the car would still move. In this case, you are expending fuel. I don't think our car has enough torque to pull itself without keeping the revs above 1.5k, though.

If you're coasting, and you drop it into neutral or clutch in, you've disconnected your wheels from the engine, hence your momentum is no longer spinning the engine. Now the ecu has to expend gas to keep it spinning.

Oh yeah and to the original question, the bog is normal.

 

I think that's the main argument, which I can see kinda explained that way. But still, from what I can tell keeping the gear engaged will slow down the car because of the engine's friction, giving you less mileage. If you can go a farther distance coasting in neutral than having a gear engaged shouldn't that overcome the gas lost by the ECU keeping your engine spinning at it's bare minimum?


[EDIT]Also, not to mention the additional wear caused on the engine by consistently keeping it in gear while coasting. The extra rotations will surely add up over time.

 

Strictly speaking about mileage and coming to a stop light (which is what the op was doing), you'd want to leave it in gear. Keep in mind all fuel usage drops to zero during a proper coast. That's technically infinite mpg. Yes, you're significantly slowed down, but you're coming to a stop light anyway.

Of course, like your example, you wouldn't want to be doing this on the freeway, going up to 85, and then coasting back down over and over. I don't think anyone will ever bother figuring out the math behind the mileage there, but yeah you'd probably waste a lot of fuel.

As for the wear, that's a totally different area that I don't want to touch haha. But I'd wonder how significant the amount of time you'd spend coasting to a stop light would be vs how much you'd be driving the car normally anyhow.

 

Mine did the same exact thing, take off the IAC valve and clean it up with some carb cleaner, theres a DIY somewhere on here or HT