Quote:
Originally Posted by polarstorm
It still burns gas at the rate that the rpm needle indicates.. you're just not making the engine work so it falls below 1k..
Careful driving in neutral, you effectively lose control of the car if you're distracted and depending on conditions.. my uncle died that way going down a 30 degree incline, couldn't put it back in gear because the tractor was loaded (a few tons) and it had picked up too much speed..
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Quote:
Originally Posted by Chimpo
I'm pretty sure that you are incorrect. Most modern F/I engines cut the injectors when left in gear and coasting. I however do not specifically know if THIS engine does or not.
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It's standard for ECU's to cut fuel to the engine, it's basically free fuel savings. This has been standard practice for nearly a decade. If you are in neutral you NEED gas to keep the engine spinning and power going to the alternator, A/C, brake booster, and other accessories. If you're in gear you can use momentum to keep all these systems spinning.
You are still hearing noises because the engine is still pumping air through the system, every time a valve opens and closes there's actually a sonic boom occurring. You can feel the car go into "compressor mode" as the engine shuts off the fuel (a little lurch forward) and if you have the instantaneous mpg on you'll see it jump to 127mpg. When you hit about 1,000 rpm the fuel kicks back on to power the accessories and maintain idle, it'll lurch forward a little bit which took me awhile to figure out.
With regards to the OP the biggest factor in fuel efficiency for internal combustion engines is how it's operated. They work best at constant load and constant speed, you'll get the best mileage using cruise control, it's thermodynamics. Stop and go is death to fuel economy, accelerating costs a ton of gas and braking turns all the gas you just used into useless heat, coasting or maintaining speed is what nets you decent gas mileage.
You'll get better mileage cruising at 100 mph than you would stop and go from 0-25 and repeat.
Edit: Basic source
http://en.wikipedia.org/wiki/Energy-...ing_or_gliding