After reading the initial post about coasting, I was going to give some input, but I see a couple of the other guys beat me to it. But I will add that I agree with them that coasting in neutral is probably not a good idea or possibly even helpful. Like they said, the injectors have to fire to keep the engine idling in neutral, whereas in gear the injectors will shut off. Secondly I think it's harmful long-term to go in and out of gear at speed. My brother used to do that with our Accord, and the transmission eventually had to be replaced. It's the only part of the 22 year old car that has had any trouble, and I don't think it was a coincidence considering the way he used it (improperly).

 

Also, what's with people writing "The best anyone has gotten for an automatic is 43MPG." Do we really have the info from every Fit owner?

 

Let's get a couple of things straight.

First of all, coasting in neutral does no harm to the transmission. None.

Second, coasting in neutral uses less fuel than 'coasting' in Drive, if the goal is maintaining your speed. If you you want to slow down, keep the car in gear and take advantage of DFCO rather than using the brakes.

Third, using higher octane fuel does nothing whatsoever to improve fuel economy. Nada, nil, zilch. If you buy junk gas, perhaps the higher octane version has more additives, in which case you might see cleaner engine internals over time. Or perhaps the junk gas you are buying adds ethanol to the 'regular' but not to the higher octanes, in which case you will also get better mileage. But it will be due to the ethanol content (or lack of it), not due to the octane. A higher octane rating only means one thing -- greater resistance to pre-ignition. Your engine either needs it, or it doesn't. The Fit engine doesn't need it.

So spend that money you would otherwise waste on higher octane to buy quality gasoline that has detergent additives in every grade. And stay away from the 10% ethanol stuff if at all possible because it knocks the heck out of your MPG.

 

I'm trying the coast process on this tank, and I'll post up the results (this Thursday's fill up should tell the tail). I'm right on target again at 203 miles at the 1/2 tank mark so this tank will probably be inconclusive. If I'm still at 40mpg + it's a wash (gear coast v.s. neutral coast) on my commute and geographic conditions.

Disclaimer mode on: Please note that the following hypothetical is based on fuel efficiency and NOT tranny longevity. That should be left to the individual who is willing to take the "chance" based on compelling factors and intelligent decisions/analysis that their transmittion might be damaged while coasting in neutral. Disclaimer mode off...

I'm still thinking mileage will be better with neutral coasting because I can't zero-throttle coast 1/2 the distance as I can while in neutral. Example is that I can neutral coast for 2 miles straight with no throttle input at 60mph and 750ish rpm for 2 minutes. At the 2 minute mark I can slip into drive pull back up to 60mph (5-7 seconds) and then back into neutral for another 1.5 miles. Total fuel used is the amount idling for 3.5 minutes and a easy throttle push at 1800-2100 rpms up to 60mph.

With the car in gear I can coast for about 1/2 that distance, or 1 minute before throttle input is necessary. Assuming the injector pulse is shut off by the ECU at 10 seconds, I'm only "off" for 50 seconds, then back on up to 60 and then "off" again for 35 seconds. Therefore the gas consumption (based on two glaring assumptions) is only zero for 85 seconds and a distance of 1.75 miles.

In summary:

Neutral:

Distance traveled: 3.5 miles
Idel time: 210 seconds (approximate)

Coasting:

Distance traveled: 1.75 miles
Injector off time: 85 seconds

Maybe this forum can help with the following parameters required for intelligent analysis:

1) Does anyone have scanguage (or other) quantatative info on fuel consumption while idling (gal's/hour would work). That would go a long way in determining if injector shut-off is actually more fuel efficient.

2) Also how long does it take for the ECU to 'shut-off' the injector pulse while coasting? I think I can feel it, but it might just be the trans down-shifting as speed and rpm is decreasing.

I'll see what I can dig up in the meantime.

-D

 

Well said wdb. I knew neutral was not harmful in a 'typical' rear-wheel drive auto-trans, but the trans-axle front wheel drive transmissions I was not 100% sure on. A quick call to my mechanic confirmed that a trans-axle operates the same as a standard auto. The pressure built from the pump at idle is more than enough to handle lubrication duties while coasting. Damage can occur however if you are not matching your rpms when going from N to D. An example would be reving to 3000rpm and dropping back into D. I'm always rpm matching when going from N to D, but blow it from time to time, but am getting much better.

Now, the BIG question I have for everyone is DFCO. Do we know for a FACT that DFCO is in effect while in OD? (Auto trans of course).

--D

 

I will refer you to the experts:

N or D while stationary? - CleanMPG Forums

 

LOL! I was just over there reading that post!

Okay looks like pcs did some SGii work on idling. His SG showed .24/gals per hour when warm in his MT Fit. As soon as I get home I'll do the calc's to see what I'm actually burning while ice on gliding (coasting) v.s. ice on DFCO. I have a feeling we're talking about $30/year or less. Not much but if it can get me over 45mpg I'll be jumpin.

--D

 

Just building on this a bit; lower octane fuel actually has more energy in it as well. There is a chance you would experience a decrease in fuel economy if you start pumping premium in there.

 

Coasting in neutral is not any different than idling in neutral. I'm saying that the problem is shifting into and out of neutral at speed. That is not good for the transmission, and I don't know if the new owner's manuals say that, but the old ones mentioned it specifically. Rockrover could be correct that "rev-matching" helps, but having replaced a transmission due to my brother's coasting silliness (back then it was for fun, not mpg), I wouldn't risk it.

 

Pirelli,

So it took 22 years for your Acura's trans to give up? If so, it would seem to me that your brothers antics actually increased the trans longevity. 22 years of operating anything mechanical is on heck of a testimony!

--D

 

No, the engine is running fine at 250k miles, the transmission was shot by 100k.

 

Ahhh. Gotcha'. That's the thing with auto's. Some crap out, others don't no matter how hard you beat them. On my rock-crawler, I've got a 15 y/o 80k miles Land Rove ZF auto in it and have beat the snot out of it since I put it in my buggy. That said, it will take a dump the next time out...

--D

 

Okay, results just in on my 3rd fill-up.

Looks like 41.5 mpg!

402.5 miles/tank
9.7 gals (same pump, one-click after shut-off).
Tires: 51 psi
5 mph under 65 speed limit...Tried to stay at 55mph but wasn't always successfull (too many folks burning/wasting gas to the next light)

Now remember this was with significantly more 'city' driving >25%, as I had my in-laws in town and I had kid duty all week. My 'city' isn't stop and go traffic.

I did keep the a/c off as much as possible. I think I had it on for approximately 50 miles on this tank (kids and in-laws were in the car).

I practiced nICE-on glide virtually every chance I had, and also DFCO glide when an imminent stop was ahead. On a few occasions I would also go ICE-off at lights greater than 10 seconds.

I'm going for 45 mpg this tank, as my hypermiling techniques are getting better (better timed and smoother). Also I shouldn't have any 'run-around' this tank and should be able to keep her >90% highway. Now that I'm more comfortable with ICE-off I'll use it more too.

Is anyone running 0w20 oil? If so, what are your impressions? I'm still 4k miles from my first change, but thought I'd ask.

--D

 

Okay, I can buy that. The same is true for MT cars; no matter how smooth we might think we are, the more we put the cars into and out of gear the more wear we cause on the moving parts. It's one of the reasons I stopped fooling around with P&G.

 

According to Hondas customer service, as well as the manual, 87 OR HIGHER is recommended. A few people with OBD readouts actually showed a timing advance with the higher octane. I definitely notice a difference... I am sure with such a global motor such as the L series it would have something in the ECU to be able to take advantage of a higher octane fuel which is usually the regular grade in some countries.

 

additionally, our engine has a compression ratio of 10.4:1 which is unusually high for such an "econobox". In comparison the mighty NSX (in which no sane owner would ever dare to use 87 in) has a compression ratio of a slightly lower 10.2:1. B16A? with 100HP/liter? 10.2:1 see what I'm saying here?

 

No that's wrong. It's been proven to be worth +10% FE

There is a technique on this that makes it so smooth you would never know as a passenger it's being done.

 

D never look at the $'s because at some point, "depending" on your miles driven per year and actual mpg it's not worth going from good to great FE
You have to do it for other reasons unless you live in a cardboard box
below is the calc


going from 40 to 45mpg @ 12000mils per year and $4/gal is a $133 saving
going from 45 to 50mpg @ 12000mils per year and $4/gal is a $107 saving
going from 50 to 55mpg @ 12000mils per year and $4/gal is a $87 saving

 

Good work.
Start P&G with FAS and you could get 50mpg if you wanted

 

Quote:

Originally Posted by pcs0snq

Good work.

Thanks for the props Paul.

I'm right at 139 miles at the quarter tank mark on this one. If I can stay out of town this weekend, I might just pull a....gulp...500 mile tank! Don't want to jinx it though! We're at 98 degrees in Santa Fe this weekend, and I just tinted my windows, so no moving them for a couple of days. Gonna' be hard not to hit the a/c button!

Now back to your mpg calcs. What am I missing? Why isn't $ savings linear?

Regardless, I agree. Can't look at the numbers too closely, or it (for me) becomes self defeating. Spending sooooo much effort for what? $ 5.50 per tank? Nope. It's the challenge! And makes my commute fun!

--D