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All of the following assumes an automatic transmission, and regards my Hyundai Elantra wherever that's significant.

I have a stretch of about half a mile where I could shut the engine off completely and coast in neutral. It's a slow, straight, downhill in heavy stop/go traffic running at less than 20mph.

But, according to the scangauge, I could run this stretch with the engine on, in gear, at 0.3 gallons per hour. It takes about 3 minutes. I figure that's about 15 thousandths of a gallon. Is that worth it? Given (and this brings us to the AT nature) that it's an automatic?

So, second question is, how bad does it hurt an AT to be shifting in and out of neutral at speed, or running at high speeds (30-60mph) in neutral?

Bonus humor: can you run an AT-AT (http://starwars.wikia.com/wiki/All_Terrain_Armored_Transport) in neutral?

You should not coast that far with the engine off in your Elantra -- the automatic transmission in that car can't take such a distance as you'll end up with metal on metal contact in there. The transmission is lubricated by a pump driven by the engine. You're okay coasting a couple of car lengths or so but I wouldn't go any further than that. Spending some fuel on the 0.5mi stretch is cheaper than rebuilding the transmission!

Exactly what I was looking for, thanks! What about shifting in and out of neutral at speed, with ICE on? I know you've said before to get the revs to match, but I can't do that yet. And what about simply running in neutral with the engine on?

neutral, engine on is always fine.

Exactly what I was looking for, thanks! What about shifting in and out of neutral at speed, with ICE on? I know you've said before to get the revs to match, but I can't do that yet. And what about simply running in neutral with the engine on?

I shift in and out of neutral at speed all the time, and nothing has gone wrong with my transmission. I tend to stay away from the NICE off coasting. About rev matching... I don't ever have to do it, because I believe my engine and transmission work together to make switching in and out of neutral at speed an action in which rev matching is not needed. I drive a 2008 Toyota Yaris, and I hope this info helps!!!

Matt

drummerboy2004... How the heck are you getting 151% combined EPA without NICE-off coasting? Nice job (pun unintended)! I hypermile our 2002 Saturn L100 with an AT to the 140's% with a fair amount of NICE-off coasting. It can be flat towed, which is all I need to know regarding NICE-off coasting not harming the tranny. But in most AT cars (including the Elantra, apparently) this isn't the case.

satyap: Although I don't have a scan-gauge, I'm convinced that DWB nets the biggest gains by far in city driving. That along with lower speeds, which is correlated with successful DWB. Shutting down at least at lights (NICE-OFF coasting up to them if you can) and light acceleration are good ones too. These tools netted me nice FE gains, so I'm passing this on to you in case you aren't focusing on these.

drummerboy2004... How the heck are you getting 151% combined EPA without NICE-off coasting? Nice job (pun unintended)! I hypermile our 2002 Saturn L100 with an AT to the 140's% with a fair amount of NICE-off coasting. It can be flat towed, which is all I need to know regarding NICE-off coasting not harming the tranny. But in most AT cars (including the Elantra, apparently) this isn't the case.

Haha! I would have to say my main tool is being able to anticipate everything! I have learned my car pretty well, and know when I should stay in gear when coasting or switch it to neutral... It's really all in making the car an extension of your self and being able to anticipate what's happening around you.

Oh, and yeah, I believe since your car is flat-towable, you should be able to NICE-off coast all day long without any excessive tranny wear. Man, if only my Yaris was flat-towable! You have a lot of potential in that Saturn!

satyap: Although I don't have a scan-gauge, I'm convinced that DWB nets the biggest gains by far in city driving. That along with lower speeds, which is correlated with successful DWB. Shutting down at least at lights (NICE-OFF coasting up to them if you can) and light acceleration are good ones too. These tools netted me nice FE gains, so I'm passing this on to you in case you aren't focusing on these.

The scan-guage is how you really get to know the car and what it can do!

I've been trying to DWB for months, sometimes successfully. Lower speeds, always. Light acceleration, for the last 2+ years. Although thanks to sgii I found I was TOO light. 2000RPM is good for the Elantra.

I did find (this may be Elantra specific): no P&G under 20, the losses are too great. Smoothly go to 20mph at 2000 RPM, then start playing tricks.

And the biggest loser is: backing out of my flat garage onto the sloped driveway (slope away from garage) with a cold engine. One day I pushed the car out and didn't start until it was in the road, and I got 27 versus <25MPG 5 miles later.

As for backing out with a cold engine: I feel I waste too much backing INTO the garage, as I do have to get it exactly right (avoid the other car in the driveway, and then park dead center). It FEELS like it outweighs the gain of nose-outing with a cold engine. Agree?

Another random fact: my commute (one way (http://maps.google.com/maps?f=d&source=s_d&saddr=Long+Point+Rd%2FState+Rd+S-10-97&daddr=32.784576,-79.956121&hl=en&geocode=FRoh9QEd7og9-w%3B&mra=mi&mrsp=1,0&sz=13&sll=32.775151,-79.946308&sspn=0.098435,0.147285&ie=UTF8&z=13), other way (http://maps.google.com/maps?f=d&source=s_d&saddr=Lockwood+Dr&daddr=Long+Point+Rd%2FState+Rd+S-10-97&hl=en&geocode=FWhC9AEdrvc7-w%3BFRoh9QEd7og9-w&mra=ls&sll=32.775151,-79.946308&sspn=0.098435,0.147285&ie=UTF8&ll=32.813247,-79.902363&spn=0.098393,0.147285&z=13)) is across a bridge that *really* kills MPG. One way, it's a steep 1+ mile climb that drops my MPG from 30+ to 25, and the other way is a gradual climb that doesn't let it get above 25. It's best to use CC there.

Oh, and I did find that part of my route, where I have to get on the frontage road anyway, is best completed by staying on the frontage road. I get better mileage that way.

I've been trying to DWB for months, sometimes successfully. Lower speeds, always. Light acceleration, for the last 2+ years. Although thanks to sgii I found I was TOO light. 2000RPM is good for the Elantra.

+1! Satyap, you and I both have 04's, and it looks as if we are doing the Newton-Leibniz thing (inventing/finding the same thing at the same time in different places). I've found it's something between 2000 and 2250 RPM (a little lower when cold outside, you can rev higher when its warm outside without any extra losses).


I did find (this may be Elantra specific): no P&G under 20, the losses are too great. Smoothly go to 20mph at 2000 RPM, then start playing tricks.

+ INFINITY TO THIS!!

I've learned exactly the same. Until you get over 20 (basically until you get the AT into 3rd), this car EATS gas like it was going out of style. After that, try to cruise at TPS 12, you might be able to use Hang Time with TPS 10 or 11 for a little bit. If you get up to 36 MPH, and get it to shift the last gear (RPM should drop to 1375), and can hang at TPS 12, IGN should rocket up to 40 and MPG will jump to 49-52 MPG. :D

Another random fact: my commute (one way (http://maps.google.com/maps?f=d&source=s_d&saddr=Long+Point+Rd%2FState+Rd+S-10-97&daddr=32.784576,-79.956121&hl=en&geocode=FRoh9QEd7og9-w%3B&mra=mi&mrsp=1,0&sz=13&sll=32.775151,-79.946308&sspn=0.098435,0.147285&ie=UTF8&z=13), other way (http://maps.google.com/maps?f=d&source=s_d&saddr=Lockwood+Dr&daddr=Long+Point+Rd%2FState+Rd+S-10-97&hl=en&geocode=FWhC9AEdrvc7-w%3BFRoh9QEd7og9-w&mra=ls&sll=32.775151,-79.946308&sspn=0.098435,0.147285&ie=UTF8&ll=32.813247,-79.902363&spn=0.098393,0.147285&z=13)) is across a bridge that *really* kills MPG. One way, it's a steep 1+ mile climb that drops my MPG from 30+ to 25, and the other way is a gradual climb that doesn't let it get above 25. It's best to use CC there.

I don't have cruise. I find that for lower speeds (30-40 MPH) I can do gentle upslopes at TPS 17 or lower. If it's over 40 MPH, get a running start of about 47 MPH and you should be able to attack it at TPS 21.


Last note, DO NOT EVER EOC WITH THIS CAR! You can FAS at a stop light, while not moving, but DON'T do it while rolling (EOC = Engine-Off Coasting). The manual says specifically "Do not drive or tow the vehichle any distance with the engine off and the front wheels on the ground.

If you take your downhill, get up into 4th gear territory (I don't know the PSL), just pop it into N and watch your iMPG jump into the 200+ area. That's the best we can hope for, you and I...

PSL at that downhill, both the steep and the shallow (they're on either side of a hump, hump being the top of the Ravenel bridge), is 55. People routinely do more, of course. But the steep downhill has me in stop-n-go rush-hour traffic. But I get your point. I once took a picture of iMPG > 300. That's right, three hundred. Sure, I was at PSL at the time.

Is hang time an effect of torque converter lockup? (And I don't know what that is, but I think I've seen it happen).

I think most Hyundais are not flat-towable. That said I have done FAS in a car with an AT, including my (former) Hyundai Accent. I didn't like the way it went back into gear though - sometimes it would jerk a bit, and this isn't something the manufacturer recommends you to do - so I quit. I haven't tried it (FAS) with my new Sonata, although I have coasted in neutral a few times.

It's not worth transmission damage, however slight. Newer Hyundais (anything sold after the 1990s) are good cars with great FE and the resale value will likely increase with each new model year.

I've been eoc'ing my car for 3 years now and while I knew wasn't good i still did cause of the numbers i could get. while it;s nice to be able to get over 40 mpg from a automatic transmission car it wouldn't be too nice if the trann took a dump and i'd know exactly why!

Soooooo I have now stopp all eoc'ing. I will still roll out of my driveway and comong up to red lights but no more long coast with engone off.

today was a good test and wasn't as bad as i thought. 34.9 to work over a 5 mile distance. coming home was much better. 38.0 over same 5 miles.

Mike, I thought you had found your car is fine for flat towing?

Sean, I knew my car couldn't be flat towed, but I still was eoc'ing. It's nice to be able to get over 40 but not if it might cost me a transmission. Also a lil hard on the battery cause I can't bumb start.

I checked the Elantra's manual. It says NO towing with front (drive) wheels rolling. So no EOC either.

I get the same jerk effect with engine ON coasting, and changing neutral to drive, at speed > 30mph.

Have you tried to rev match?

I checked the Elantra's manual. It says NO towing with front (drive) wheels rolling. So no EOC either.

I get the same jerk effect with engine ON coasting, and changing neutral to drive, at speed > 30mph.

Yep, that's what I mentioned earlier. You can shut down at a red light, but don't shut down and roll up to the light with the engine off.

Have you tried to rev match?

I don't know about satyap, but I know mine does bizarre things when it comes to rev-matching. If I go from N to D, it'll rev WAY up (to like 2900 RPM), then drop down to relatively appropriate, and THEN shift into gear and lock up.

If I try to rev-match, and bring it up to 2200 RPM, and then shift from N to D, it does the same thing - revs WAYYY up (to 3500-3800 RPM), and then drops back down in.

This is for high speed. At middling speeds (30-45), I can rev match normally. Under 30, no rev-match needed really.

Odd. What happens if you blip up to just over the correct RPM, let go and then shift so that D is engaged as the RPM is falling toward what is required for the road speed in top gear?

I'll let you know tomorrow. :)

*EDIT* I haven't had a chance to really test this as I've driven the "super MPG" route home that's lower speed and doesn't really give room to poke this. In the mornings I keep forgetting what I'm supposed to be testing. I'll remember today. :)

I just looked up towing on my 2010 honda insight and it says i can flat tow up to 50 miles at 35 mph. I believe this gives me a green light to fas with ice-off. Anyone not agree?

Most Honda automatics specify the same limitation as yours - below 35mph. And many AT Honda owners use FAS with no issues at all. Since the Insight will autostop on its own depending on road speed, engine load, and state of charge, forcing the shutdown might not add significantly to the trip MPG. It may even degrade it a bit if the engine needs to run to charge a depleted hybrid battery because you missed the regen opportunity by coasting to a light while letting the IMA do its thing.

Generally speaking - When it comes to reading the manual for flat towing limitations, it is important to confirm that the specification provided is for all four wheels on the ground. When I was checking the 2011 Sonata manual for flat towing capablities, it said that it can be flat towed and then the next sentence stated that the front wheels must be placed on a dolly. So FAS is a no-go for that car even though it says it "can be flat towed". In the manual for my Chevy, it says ok to flat towing with all four wheels rolling up to 65mph. But for the SS version (with a different transaxle), it says the front wheels need to be placed on a dolly, and it even has a little drawing of the nose of the car with the wheels on a tow dolly.

If in doubt, it's better to leave FAS on the table and avoid potential transmission problems.

I just looked up towing on my 2010 honda insight and it says i can flat tow up to 50 miles at 35 mph. I believe this gives me a green light to fas with ice-off. Anyone not agree?

That's what my Odyssey says as well. I FAS it up to 45 mph or so in short stretches, usually approaching a stop or slowdown.

I figure that 1/4 mile, starting at 45 mph and quickly dropping below 35, will be much less stress on the transmission than 50 miles of continuous 35 mph.