Defeating start-stop


Start-stop is a feature in some vehicles which turns off the engine in prolonged idle such as waiting at a red light and automatically restarting it when the brake pedal is released. The intent is to reduce fuel consumption and vehicle emissions.

Some people get used to this seemingly unnatural behavior. Other people hate and even despise it. At issue is whether the extra wear and tear shortens the life of the battery and starter motor.

Some vehicles allowing disabling start-stop in the vehicle configuration options. Others have a button on the dashboard; pushing it soon after starting the engine disables start-stop until the next time the vehicle is turned off and back on.

It has been previously reported that some vehicles equipped for towing disables start-stop when it detects a connection to the trailer lighting socket.

On the Car Pro radio show this morning, the host reported that shifting into low when stopped at a light disables start-stop on the vehicle he was driving. As they like to say, your mileage may vary…


@Bill, While your post seems to just be a statement, it did make me wonder one thing, How much fuel is saved by the start-stop? I know of the prius it can be a supreme savings in gas as the electric motor can drastically lower the amount of cycling. But, on the gas only cars what do we think the saving can be? Could this possibly be a net zero on the cost side, when considering the saving on gas? If this is the case we would also have a net positive of less exhaust pollution if the money is zeroed out.

Here is an interesting article talking about Start/Stop systems,

It claims many of the components have been re-engineered to handle the larger duty cycles involved with the practice. Also, the saving seem to be a 3% to 5% increase in fuel economy due to the practice.

Also, the article claims that every car with the feature has some manner to disable it, but they all must be activated each time you start the car.


We drove a Chevy Cruze last year when I was in York, Pa. I did not like that auto-start stop. It gave me one more thing to look out for if I ever buy a new car again.


Oooo! This is right up my alley.

A modern car engine idling is about .5 gallons per hour. So, stop start saves a couple teaspoons per activation. Stop start pencils out from a cost perspective. And there are no durability concerns (know what else uses stop start? Every hybrid sold ever) that have cropped up.

The little A with a circle around it is usually your auto stop start disable button. Technically, automakers aren’t required to re-enable the system with each ignition cycle, but it’s required to claim the off-cycle credit. “Off cycle credits” help automakers hit their fuel economy targets. The technologies constantly change, but here’s a slightly dated example of technologies that give automakers these credits (

There’s a ton of ways to reactivate the engine when stop-start has decided to shut it down:

Reduce brake pressure, turn steering wheel, turn HVAC on with AC use, battery charge low, transmission or battery temperatures high or low, hood latch unlocked, open a door, etc. There are a shitload of things that bring the engine back to life.


Just to be pedantic here… A full time (?) hybrid like the Prius doesn’t use a starter motor for start stop. It doesn’t actually have a starter motor, it uses one of the main traction motors for starting the engine, which are much less prone to any wear issues than a typical starter motor.

I’ve always assumed engines using start/stop have specialized starter motors that are more suited to the constant starting of city traffic.


It’s been done a few ways by different manufacturers, but in the case of Toyota, you’re correct, starting duties are handled by either MG1 or MG2 (I forget which). For non-hybrid stop start systems, you’ll typically get a beefier battery, starter, and some specialized engine internals due to increased no oil pressure engine operation time.

However, there are conventional engine start-stop systems that don’t use the starter motor either. They will stop the engine just past TDC and ignite some fuel to start (saving starter wear). See Mazda.


I hate it. I think it’s a safety thing if you ever have to stomp the gas at an intersection to avoid an accident.


None of my POV have it, and only 1 rental car to date had it. This was in Wisconsin in September, and after flipping my whig slightly (because I didn’t know the car I was in did that) the first time, I don’t remember noticing any more…
I wonder how much difference this feature makes in Texas. We’re running A/C and/or heat virtually any day of the year, and I hear those things kill it (Bill’s post suggests others have similar impressions). But it’s been popular in Europe for the last decade or so, so maybe it’ll catch on here…like CVTs did… :stuck_out_tongue_winking_eye:


There is probably a message you can send over the CAN bus to disable it, which would be the same as pressing the button. A small microcontroller could be used to do this every time it detected an engine start.


The wear and tear might be a problem for first generation models with this feature. In time this won’t be a problem because designs will improve just like any other automotive feature has improved in the past (electronic windows, automatic transmissions, electronic fuel injection, anti-lock brakes, etc.). The fuel savings are real but in the single digit percentage range. Do a search for independent test because there are many out there. When you scale the numbers to hundreds of thousands or millions of vehicles over many years the fuel savings are significant. I haven’t seen any measurements for how long it takes to start but my guess is it’ll take less time than it takes to release the brake and push the gas pedal with your foot. Measuring the startup time could be a fun project. Real data would be a lot more interesting to discuss than FUD.


While doing some searching on the topic I came across this. Mazda isn’t using the traditional starter to start the engine in this stop-start use case. They’re saying it takes 0.35 seconds to start. Cool technology. Stupid name.


My vague recollection of the start stop system was when BMW first introduced it was that it did not improve fuel economy more than 10%, more like what kinosh said.
It’s a last few percent thing at the time it was released. Over 10 years ago, iirc.
It was intrusive.
No one in the room that tried it liked it.
Everyone asked where the over ride switch was.
On the Prius is is less intrusive but you can feel the car/engine jerk a significant amount when it fires up the combustion engine and the car is in “P”.


One wonders how well this works with leaky valves and rings as the engine ages. :slight_smile:


Not all all, the vehicle won’t be around long enough.
Starter motor and battery lifespans and the labor to replace them may be affect the fuel savings - oh but wait those headaches are never taken into consideration after the fact.


GOOD consumers turn their leases in at the 2 year mark with less than 20k miles accumulated.
After we lease those used vehicles to their first Certified Used Auto Leaser, who also turns in the lease in 2 years and having accumulated less than 20k miles, our products are well within operating standards and will have no measurable loss of performance as we end-of-life them. If any (horrible, horrible) consumer chooses to ignore social, political, and societal pressures, or is so unlucky as to have a need to try to (against our advice and common wisdom) extend the service of our products beyond this reasonable framework, be it on their heads.
– Every Modern Auto Maker
PS we are also lobbying Washington D.C. to pass legislation making such foolish and willful, not to mention stupid, exploitation of our product not only inadvisable, but unlawful. Soon, so shall it be and then; Glory Day! Your concerns will be even further from having merit than they already are.
PPS: Leaky rings and valves pollute. Don’t pollute!


The hosts of the show reported that the A/C did not work well on a humid day when the engine has stopped for more than a few seconds…


The hosts reported that there were third-party accessories available for that purpose and they intend to test and report back on them.


Chitty Chitty Bang Bang?


You mean that when the accessory belt-driven compressor shuts off the AC condenser’s temperature equalizes with the return air being blown over it? Color me astounded.


You’re not wrong, and people have done this.

The simpler way is to send a CAN/LIN message at each startup that says you pushed the auto stop-start button.