View Single Post
Old 08-09-2012, 03:30 AM   #40 (permalink)
Drive less save more
ecomodded's Avatar
Join Date: Jul 2011
Location: Vancouver Island, Canada
Posts: 1,189

Dusty - '98 VOLKSWAGEN Beetle TDI
90 day: 60.42 mpg (US)
Thanks: 134
Thanked 162 Times in 135 Posts
here is that botched article from PM online.
All the same tomorrow i am going to test my car by coasting with the ignition off in gear then switch on the ignition and listen/feel for any change,like wise by testing with the ignition on in gear then switching it off.
Bust this myth, one way or the other.
I think the "Scangauge" reads injector pulse durations and has a function to read them,it would be useful to bust this Myth.
if anyone has one, take some readings while coasting in gear, engine on, its somewhere in the Scangauges menu.
No need to test with engine off as it will most definitely not be injecting any fuel.

the Article, finally !

Tactic No. 6: When Coasting Downhill, Leave the Car in Gear

There are those who refuse to be shaken from the practice of coasting downhill in neutral to save gas. This is a bad idea no matter how you look at it. Let's set aside fuel economy for a moment. Coasting downhill in neutral is illegal in most states. And it's dangerous in all states. In neutral, you have no way to accelerate to avoid a hazard, and if the engine stalls, you have no power steering or vacuum boost for the brakes. If the hill is steep enough to call for hitting the brakes to keep you from gaining speed, they're more likely to overheat—and overheated brakes lose effectiveness until they cool off. They'll probably do that right around the time the police show up to take the accident report.

Here's the surprise: There's no tradeoff between safety and fuel economy in this case. Leaving the car in gear while coasting downhill actually is more efficient. Why?

Most fuel-injected engines today use computer-controlled Deceleration Fuel Cut Off: When you lift your foot from the gas while leaving the car in gear, injectors shut off automatically, and the car's rotating tires—which are connected to the engine via the transmission—keep the engine turning and the accessories running. So, the engine consumes no fuel at all while the vehicle is coasting downhill.

In contrast, the fuel-consumption rate for an engine idling in neutral falls between 0.2 and 0.4 gallons per hour (gph). Splitting the difference and using 0.3 gph for our example, idling in neutral down a -mile-long hill consumes fuel for 30 seconds, for a total of about 0.32 ounces of gas. Popping the car into neutral actually wastes gas.

This may seem counterintuitive, but that's what data are for—replacing good guesses with solid facts. Watch the data, and over time the savings will take care of itself.

Read more: Driving Tips to Save Gas - Memorial Day Weekend - Popular Mechanics

Driving Tips to Save Gas - Memorial Day Weekend - Popular Mechanics
Save gas
Ride a Mtn bike for errands exercise entertainment and outright fun

Last edited by ecomodded; 08-09-2012 at 04:13 AM..
  Reply With Quote