The single most important improvement to FE you can ever do. FREE.
Two days ago I drove 20 miles to the top of a mountain near me. I wanted to do a concrete test of the benefits of Engine Off Coasting in a manner that anyone can understand. I already know that this is the longest coast in my area.
My test would compare Engine OffCoastinginhigh gear with EngineOff Coastinginneutral. Engine on coasting can only be worse in each case.
Turned out to not be much of a test at first. In gear, car would not even roll downhill on a sizable grade. No problem with that in neutral.
So I decided on a running start from 55 MPH for each scenario. I would travel down the mountain till car speed slowed to 30 MPH, stop and note the miles travelled, immediately turn around and drive back up to the start.
1. Engine Off Coast in 5th gear. Car slowed immediately after engine was shut off. Fastest speed recorded with ScanGauge was 53 MPH. Average speed was 36 MPH. Distance travelled 5.1 miles, much of it near 30 MPH. Even so, no fuel was used. Turned around and drove back up mountain to start. At that point, SG current trip 47.2 MPG for 10.2 miles. This is a climb that would indicate about 25 MPG without the coast being involved.
2. Engine Off Coast in neutral. Car gained speed from the start. Fastest speed recorded 76 MPH with hitting the brakes twice to stay near 75 MPH. Average speed was 56 MPH. Distance travelled 8.7 miles. No fuel used.
Turned around, drove back to start. SG current trip 67.4 MPG for 17.4 miles.
This amounts to 70% more miles travelled and +20 MPG over the 17.4 miles.
I ran each test a second time and results were so close they don't bear repeating.
I attribute much of my FE success to this very thing. I honestly believe this is the single most important ingredient of my FE. And it's all FREE.
Yesterday I drove the coasting route used in tests above. Coasting speeds were significantly higher at every point. Where I had braked twice before to stay close to 75 MPH, I had to brake 6 times yesterday.
When I reached the point where I had slowed to 30 MPH before, I was going 40 MPH yesterday. This extra 10 MPH allowed me to clear a rise at 32 MPH that I had never cleared in many tries at any speed. There was enough additional downgrade to coast another 3.8 miles till I slowed to 30 MPH.
This coast was 12.5 miles vs 8.7 in original test. These runs were Engine Offin neutral.
Reminder. Coast with Engine Offin 5th gear till slowing to 30 MPH in original test 5.1 miles. I did not repeat this run yesterday because of the obvious uselessness of doing so. Yesterday's coast was near 2.5 times as far.
Don't you think everyone should be Engine Off Neutral Coasting at every available opportunity? Even if you have to make your own opportunities.
I've been warned not to EOC with an auto tranny unless the manual has no cautions about towing with the drive wheels on the ground. For example, my Mazda MPV manual says that if you have to tow with the drive wheels on the ground you must not exceed 35 mph and 35 miles. Something to do with lubrication.
I'm not a mechanic, but I know that the effect of EOC is the same as towing, it's just that gravity is moving the car instead of a tow truck.
Shouldn't there be a warning about this as a sticky note at the beginning of threads about EOC?
But at 60 mph with a larger ICE that gets .5 gallons per hour in idle, you're still getting 120 mpg at 60 mph, or 60 mpg at 30 mph. Beats my 22 mpg highway rating.
But then, if you're coasting really slow, like five mpg, you're only getting 10 mpg. I suppose if you're coming up to a long light, you could turn the engine off at 35 and EOC to the light and wait, and save more.
But how much abuse can a starter take? From a pure cost point of view, it might not be so great unless you reserve it for long waits.
I personally would not EOC with an automatic regardless of being able to tow with the drive wheels on the ground. As you pointed out, there's still significant benefit to pulse and glide with the engine idling and virtually no risk of transmission damage or increased starter wear.
My manual gearbox cars however rarely see additional starter use from EOC'ing, as I bump start 90% of the time as I near a stop unless I anticipate being stopped 30 seconds or more.
Bobsterz, your concerns are real and appropriate. Do not EOC with an automatic unless it says you're safe for full wheels-down towing. The transmission depends on the input shaft (the engine) to run its oil pump and keep it cool. If you tow at 35mph, it probably wasn't very hot when you started; but if you drive and then EOC at 35mph, it may be hot when you kill the engine.
Starter wear doesn't seem to be a problem who people who EOC and use the starter to restart, they claim normal life from their starters and batteries. However it seems like a better idea to bump start (obviously, for manual transmissions only) if you EOC on a regular basis (except then you worry about wear to the clutch and the synchro in whatever gear you use).
Not to be mean but it's obvious that you would get better FE when coasting down a hill with the engine off. Thats just common sense.
The only test that would have been almost worth while would be coasting in Neutral with engine on, and coasting in gear with engine on.
Rather then that if you thought you wouldn't get better milieage with coasting in N with the engine off there is something wrong.
In my '97 Escort Wagon I often start a coast in gear and then if I see the hill is steep enough to maintain a decent speed shift to neutral both with engine on and often see the scan gauge jump as much as 100+ mpg when I shift to neutral. I have coasted down mountains in neutral with the engine running and experienced 350+ mpg according to the scan gauge.
Thats all i've been using it for. just to compare diff situations. not for absolute numbers. thats why i don't post in the daily updates thread any longer. my last tank was showing just under 30 on the SG but when i refuled was almost 32.
There is an adjustment where you can adjust the amount of fuel you actually added to the car and If you will use it your scan gauge readings will be more precise. My last tank the scan gauge was off by 2 tenths of a mile per gallon, but I had to use this adjustment to get precise readings.
Will someone please answer a question for me about the Scangauge? All this dependency on Scangauge readings causes me to wonder...how (if at all) is the Scangauge calibrated? Is there a calibration step? How? -Ted Hart
The scan gauge gets it information from the ECU, but there are also manual calibrations that can be made if necessary. The calibration is to be made when you fill the tank if you don't put in the same amount of fuel the ECU says it has used you can enter that information which makes the scan gauge recalibrate everything on the next tank and all tanks thereafter unless you make another change.