Does EOC work as well with automatic transmissions as manuals?

[ChewChewTrain]

From super cars to family cars, manual transmissions are becoming more scarce each year.

My favorite hypermile technique is EOC (engine off coasting, for you newbies). Is EOC just as effective with automatics as it is with my manual transmission?

[Jay2TheRescue]

In most automatics, the transmission pump is not running when the engine is off, so the transmission is spinning with no lubrication. Look in your owner's manual. If it says that your vehicle is "flat towable" then you're ok. I know the CVT in my Escape Hybrid is flat towable, but most cars aren't.

[ChewChewTrain]

Originally Posted by Jay2TheRescue

In most automatics, the transmission pump is not running when the engine is off, so the transmission is spinning with no lubrication. Look in your owner's manual. If it says that your vehicle is "flat towable" then you're ok. I know the CVT in my Escape Hybrid is flat towable, but most cars aren't.

Oh. So this sounds like a "loophole" in our game, so to speak, that gives an advantage to manual transmission drivers.

Jay, I like the Mini-Stats feature. Would be nice to have a box saying MPG over X number of fillups. That way, folks that have started to get the swing of things don't have their early day, MPG stats affecting their recent good behavior.

[Jay2TheRescue]

Yeah, I'd prefer it was the way it was under the old GasSavers.org system, where the badges showed the 90 day average, so you can see what the vehicle is doing now. That way if you make mods, or improve your driving technique, it would show more readily.

[Draigflag]

When you visit someone's dashboard, you see thier "running MPG" I.e. The last 10 fuel ups (for me that's a year anyway) but you can set your own mini stats, of which other users will be mirrored when you visit thier profile.

[ChewChewTrain]

Originally Posted by Jay2TheRescue

Yeah, I'd prefer it was the way it was under the old GasSavers.org system, where the badges showed the 90 day average, so you can see what the vehicle is doing now. That way if you make mods, or improve your driving technique, it would show more readily.

Jay, once in a while my dashboard says my Civic is the "Best in Category" or something like that. Why does that happen when there are two other cars posting better (albeit dubious) overall MPG?

[Monzsta]

Although most automatics don't circulate oil when EOC'ing there's enough residual lube there to not worry about it as the components are free spinning and not doing any load carrying work, and the next period of running with the engine on isn't that far off the horizon. It is a lot more awkward and more work for the starter as with an auto you can't bump the clutch at the last minute.

That being said, flat towing is a no no, and as much of a boner as a mountain grade would give you I'd probably idle the engine on long decents in gear. Better for the brakes, and the fuel injection performs its own DFCO (Deceleration Fuel Cut Off) for you noobs.

[R.I.D.E.]

I would never EOC any automatic transmission. They require oil pressure to operate servos. The primary pump is driven by "ears" off the back of the torque converter, which in an auto is the flywheel and starter ring gear as an assembly. Neutral coasting, engine on, works great and will give you MPG in the hundreds at any decent speed. Seen too many trashed by being towed with the driven wheels on the ground. The outer shell of the torque converter is directly connected to the engine, same as the flywheel in a manual and is balanced the same as a flywheel.
A dual clutch automated manual which is basically a manual MIGHT survive extended EOC, but is it worth the risk? It's going to take a heck of a long time saving 10% in fuel costs, with a repair bill in the thousands and some I have seen can never be repaired with internal parts basically welded together.

[SteveMak]

Originally Posted by Jay2TheRescue

In most automatics, the transmission pump is not running when the engine is off, so the transmission is spinning with no lubrication...

It's important to understand what one means when they say "the engine is not running." There's a world of difference between...

1. Putting the vehicle in neutral with the engine OFF and towing it, versus...
2. The engine spinning (showing RPM at normal operating range) while the fuel management computer shuts off the fuel supply (i.e., "engine off coasting")

In most modern vehicles, if you're driving down a hill and you take your foot completely off the throttle, you'll see your instantaneous fuel consumption gauge go to zero (or infinite MPG). That's telling you that you are safely traveling while consuming no fuel. This happens only when the engine is engaged with the transmission (i.e., not in neutral), and the drive wheels are causing the engine to rotate. This works equally well with manual, automatic, and Constantly Variable (CV) transmissions.

A car designer would commit a huge oversight if they allowed your vehicle to harm itself simply my releasing the throttle while going downhill.

[Jay2TheRescue]

Yes, but in fuel cutoff mode, the engine is still spinning, even though the fuel injectors are off. The transmission pump is still spinning.