Manualhybrid - Fuel Economy, Hypermiling, EcoModding News and Forum

Manualhybrid · 11-05-2015, 06:53 PM

I turn off my engine and coast when I can. I have doubled my fuel economy using this technique along with gentle acceleration and cruising in the lowest speed of my highest gear: My personal best is 40 mpg in my 2004 Toyota Matrix XR, front-wheel-drive, automatic transmission with Thule racks. I wonder whether other folks coast with the engine turned off and what they've learned.

darcane · 11-05-2015, 08:09 PM

Quote:

Originally Posted by Manualhybrid

I turn off my engine and coast when I can. I have doubled my fuel economy using this technique along with gentle acceleration and cruising in the lowest speed of my highest gear: My personal best is 40 mpg in my 2004 Toyota Matrix XR, front-wheel-drive, automatic transmission with Thule racks. I wonder whether other folks coast with the engine turned off and what they've learned.

Welcome! I'm also in the Greater Seattle area.

Engine Off Coasting (EOC) is a widely used technique on this site. You are doing something unusual though... your car has an automatic tranny. The majority of automatic transmissions will be damaged by coasting with the engine off because lubrication to the transmission is powered by a pump run off the input shaft. Turn the engine off and you lose lubrication.

Have you verified that your transmission is OK to be flat-towed?

cowmeat · 11-05-2015, 08:56 PM

I learned that you go through clutch plates at a faster rate

Then again, I got some pretty high mpg tanks when I was driving Black Widow. Don't know that I'd tray that in an automatic, myself. Might be easier for you to see a gain in mpgs by pulling those racks off the top of the car

Manualhybrid · 11-05-2015, 10:08 PM

Quote:

Originally Posted by darcane

Welcome! I'm also in the Greater Seattle area.

Engine Off Coasting (EOC) is a widely used technique on this site. You are doing something unusual though... your car has an automatic tranny. The majority of automatic transmissions will be damaged by coasting with the engine off because lubrication to the transmission is powered by a pump run off the input shaft. Turn the engine off and you lose lubrication.

Have you verified that your transmission is OK to be flat-towed?

I appreciate knowing this term, EOC. To be clear, before I turn off my ignition, I move my automatic transmission selector from 'D' to 'N'--so I coast in neutral. Do I still need to be concerned about transmission lubrication if I coast in neutral with the engine off? Thank for your reply, Darcane (or others).

elhigh · 11-05-2015, 10:45 PM

Yes, you absolutely need to be concerned. Toyota themselves specify that a Matrix must NOT be flat towed with the automatic.

That's the same as coasting with the engine off. Don't do it.

Back in the day the manufacturers figured out that they could build the transmissions with only the front fluid pump, as the rear one was superfluous; as long as the engine was running the front pump was turning, providing fluid throughout the entire transmission. The rear pump, attached to the output end of the transmission, was unneeded (IIRC Ford was the last company to include the rear pump as a matter of practice, so it was still possible to push-start auto-equipped Fords for a while).

Rolling short distances at low speeds is one thing, but coasting at speed will destroy your tranny.

Manualhybrid · 11-06-2015, 01:57 AM

Many thanks to elhigh and darcane! One last clarification question: While my 2004 Matrix 2WD Automatic should NOT be operated EOC, is this also true if the engine is off but the ignition is turned to 'ACC' or 'electronics on'? In other words, does the transmission fluid circulate ONLY if the engine is turning? Thanks very much.

elhigh · 11-06-2015, 09:29 AM

If the engine isn't turning, the transmission is not receiving lubrication, regardless of what the ignition switch is set to. It's what the input shaft of the transmission is doing that matters. You'll have to do without EOC.

There are other Matrices in the Garage listing - and start one for yours, by the way - but unfortunately most of their owners are not actively participating. And I see that they tend to be cellar dwellers. It's a nippy tall hatchback, I'm certain it can do better than the low-30s, high-20s I'm seeing.

Xist · 11-06-2015, 03:35 PM

What is an automatic transmission doing while in neutral, with the engine off? What needs to be lubricated?

gone-ot · 11-06-2015, 04:44 PM

Quote:

Originally Posted by Manualhybrid

I turn off my engine and coast when I can. I have doubled my fuel economy using this technique along with gentle acceleration and cruising in the lowest speed of my highest gear: My personal best is 40 mpg in my 2004 Toyota Matrix XR, front-wheel-drive, automatic transmission with Thule racks. I wonder whether other folks coast with the engine turned off and what they've learned.

I was able to get 40+ mpg with my 2009 Pontiac Vibe (Toyota Matrix clone) with 1.8L 4-speed automatic...without shutting engine off...just nudging the shift-lever into Neutral. I know this is "safe" on the 2009 models, but I'm NOT sure about the 2004 vehicles (I have both).

Manualhybrid · 11-06-2015, 05:08 PM

You can read the earlier posts. I too thought it would be fine to 'Engine Off Coast' my automatic transmission car in neutral, but I've been educated that on most automatic transmission cars, if the engine is not turning, lubrication is not cycling through the transmission components. Those cars that can safely 'EOC' are approved for "flat towing", also known as "dinghy towing". Those that are not approved for "flat towing" cannot be 'EOC'd safely due to the lack of transmission fluid circulation with the engine off. A list of vehicles approved and not approved for "dinghy towing" is available here: at motorhome (dot) com (forward slash) download-dinghy-guides