The Environmental Costs of ASS

Print Friendly, PDF & Email

ASS may save gas – but it’s not so good for the environment.

There is a warning to be found in some new car owner’s manuals – which will probably be redacted once the problem is discovered. Or rather, made public.

It reads –

To minimize the possibility of catalytic converter damage: Do not shut off the engine or interrupt the ignition when the transmission is in gear and the vehicle is in motion.

ASS – automated engine stop/start – ought to read the owner’s manual.

It repeatedly shuts off the engine and on-purpose at every red light and will also shut it off if the car stops moving for some other reason – such as to place an order at a drive-thru window or because traffic momentarily congealed.

It does so to “save gas” – though not much. At least, not much on a per-car basis. An ASS-equipped car might use 1 percent less gas than an otherwise identical car without ASS.

It’s not a big selling point.

But ASS is being installed in most new cars not because buyers are clamoring for the less-than-1-percent improvement in mileage that attends repeatedly stopping and restarting the engine but because it helps the car companies meet federal MPG minimums, which are calculated on the basis of “fleet averages.” That additional 1percent per car matters – to the manufacturer – when factored over tens of thousands of cars.

Which is why almost all 2020 model year cars come with ASS, like it or not.

The driver – for whom the owner’s manual was written – has no control over this. Especially lately, in ASS-equipped cars that haven’t got an ASS-off button which the driver can use to keep the engine from shutting off at every red light, drive-thru window and momentary pause in the flow of traffic.

Not that it makes any difference to the catalytic converter – the most critical emissions control device in a car – whether the engine is shut off repeatedly by the driver or by ASS.

Either way, its ability to convert harmful emissions – the actually harmful ones, not carbon dioxide – may be compromised – and its life reduced – by the constant off-on cycling that comes with ASS. Which almost all new cars (and trucks and SUVs) come with as part of their standard – and so unavoidable – equipment package. 

The problem – soon to be redacted – with repeatedly cutting off the engine with the transmission in gear is the possibility of not-quite-complete combustion; of excessive gasoline vapors getting into the exhaust stream because of combustion interruptus – and fouling the converter.

Cats also like consistently hot temperatures to convert combustion byproducts into harmless compounds. But when the exhaust isn’t flowing because the engine isn’t running, the temperature varies – and what effect will all that erratic operation have on catalytic converter performance and longevity? Will a new car’s converter – some new cars have several converters – be working up to snuff 12 or 15 years from now?

Where’s the EPA?

Shouldn’t it be of concern to the Environmental Protection Agency that ASS might affect a car’s emissions by affecting the performance – and longevity – of its catalytic converters?

Apparently not.

For the same reason that the National Highway Traffic Safety Administration isn’t much concerned about the effect on safety of drivers tapping and swiping built-in touchscreens, only the ones they carry with them in their pockets.

ASS isn’t good for the environment in other ways, too.

The 12 volt battery which starts the engine is filled with environmentally unpleasant materials – about 50 pounds’ worth. When batteries can’t hold a charge anymore, they get chucked – sometimes in the woods.

Sometimes in dumpsters.

People are supposed to turn them in for recycling, of course – but that doesn’t always happen. And even if it does, if it’s necessary to replace a car’s battery a year sooner – because of ASS – then it means more batteries out in circulation as well as more batteries that will end up in the woods and dumpsters and so on.

More batteries will be needed – and thrown away – because ASS is hard on 12 volt starter batteries. The one in your 2020 model year car is not fundamentally different from the 12 volt starter batteries used 50 years ago.

They are among the very few things about new cars that aren’t new.

But they were designed to start the engine on the assumption that it wouldn’t be turned off for awhile. The idea was to get it running – not repeatedly get it running.

It takes energy – charge – to spin the starter and get the engine running. This depletes the battery’s charge, but just a little. Once the engine is running, the battery is recharged – by the alternator, which is what produces electricity to run the engine once it’s actually running as well as to “top off” the starter battery.

!2 volt batteries were made just large enough – and just strong enough – to handle that.


Subjecting12 volt starter batteries to ASS – stop-start/stop-start/stop-start – will mean replacing them more often. And that will mean more lead and acid in dumpsters and the woods, as well as more plastic for battery cases – the plastic being made using petroleum and by machinery not solar-powered.   

But the good news is your ASS-equipped car might use a bit less gas. You might even notice a whole number’s difference.

Got a question about cars, Libertarian politics – or anything else? Click on the “ask Eric” link and send ’em in!

If you like what you’ve found here please consider supporting EPautos. 

We depend on you to keep the wheels turning! 

Our donate button is here.

 If you prefer not to use PayPal, our mailing address is:

721 Hummingbird Lane SE
Copper Hill, VA 24079

PS: Get an EPautos magnet or sticker or coaster in return for a $20 or more one-time donation or a $10 or more monthly recurring donation. (Please be sure to tell us you want a magnet or sticker or coaster – and also, provide an address, so we know where to mail the thing!)

My latest eBook is also available for your favorite price – free! Click here.  If that fails, email me at and I will send you a copy directly!


Share Button


  1. Used to be that when your starter went out you were in your driveway or a parking lot, where you last shut your vehicle off. Now with ASS there is a good chance it will die at a stoplight or the drive through during rush hour.

    This will be fun when all these new cars with ASS start reaching the end of starter life.

  2. I have a 2018 Ford Focus RS, which has ASS. I dug around under it a bit, and the starter motor is quite oversized compared to a car without the feature. The battery is different as well, meant for constant punishment. It’s more expensive, but give the mass of additional lead plates, I suspect it’ll do fine. I’ve not been driving the car much, so the battery isn’t full enough for ASS to engage, and it’s always off on its own (says the car’s not ready for it), and also, when the A/C is working hard, the ASS wont stop the engine either. Ford took care to give this thing longevity and make it less annoying.

  3. I dont believe the last VW Passat I rented had ASS. It was a great car overall. No obnoxious head rests – great sight lines. Really well designed. If it only had a manual –and yes that awesome diesel that was robbed from us. Still the best you can get in a modern car I think.

  4. Most of the small-ish SUVs we test drove had ASS, and didn’t have a spare tire. Toyota is one of the few exceptions to this. And most the safety features can be permanently turned off. The only one I thought didn’t help avoid accidents, the drunk driver / lane keep “assist”, got turned off soon as I got the keys.

  5. The goal seems to be to make vehicles more disposable.
    Every time I turn around there is a new environment saving idea that requires more resources from the environment to make work. Sure it will save some resources here but cost a lot more elsewhere.
    It’s the same thing I’ve seen in corporations that I named “ledger theory”. What would happen is someone would decide X would mean a cost savings in A but never look at B where the cost increase from X exceeded the savings in A. Of course people got promoted for this nonsense so it happened a lot and the bigger the company the more easily it could happen. But that’s who makes these decisions on regulation, the same sort of social climbers who want to look good and advance can could not care any less about the environment.

    As to ASS specifically, it also slows down people getting going when the light turns green thus can result in motorists waiting at light for multiple cycles. If traffic is heavy enough this can mean the difference between flowing traffic and stop and go traffic jams. Which of course cancels out the savings of ASS and then some.

  6. Incomplete combustion, as you mentioned, is the chief reason the hoopties of old polluted the air with actual toxic smog. But just when we’ve perfected technology such as EFI, PCV and EGR systems, and catalytic converters to the point where most of the exhaust is CO2 and steam, along comes ASS to ruin it all.

    I think another point of ASS is planned obsolescence such that it makes cars break down sooner such that people who have their starters, batteries, and catalytic converters conk out just say the hell with it and buy or lease a new car.

    • Not to mention catalytic converters are EXPENSIVE-especially when your car has 2 or 3 of them! Having 3 of them could easily turn an exhaust system replacement in to a 4 figure job…

    • “But just when we’ve perfected technology such as EFI, PCV and EGR systems, and catalytic converters to the point where most of the exhaust is CO2 and steam, along comes ASS to ruin it all.”

      Don’t forget the “climate change” religion! This is why I despise modern society. Despite the air being a hell of a lot cleaner than it was, say, 40 years ago, the (western) sheep still believe that the air is somehow heavily “polluted” and that we must take “drastic action” to reduce CO2 “emissions”. I’m willing to bet that when/if compressed air powered vehicles come to market (yes, they exist), then suddenly, we’ll all start dying from oxygen “poisoning”. 😂 Of course, the majority of us here know the true reason for the mass hysteria.

  7. I think this is another excuse to force to scrappage of cars sooner – its becoming obvious in the UK, where one of the main reasons to scrap a car is exhaust issues. After a while they go bad, and once they go bad on a car more than say 10-15 years old (especially a basic car) its not worthwhile fixing it. My friend just had this on his car – a mid 2000s Honda Accord. Works perfectly as a car, doing what its meant to do. The check engine light came on so he took it to the mechanic. Mechanic said its something with the “emissions control system” Turns out he needs a new cat converter. Which is 2k. The car is worth 1k. Now under normal circumstances one would say “screw it” and just keep driving it. But because its now in the computer, once the car goes for the annual MOT (a test the government requires our cars to take to make sure they are safe and allow us to drive them) if a car has any issues on the emissions system – the car will not pass the MOT!! Hence a perfectly good car has to be scrapped (sorry “recycled”), because somehow that will be better for the environment. And this is before ASS gets into the picture, making stuff more complicated as always….

    • I would still repair the Accord. While on paper, the car is only $2k, the future value is likely much more as cars like it become rarer on the streets. It will take a long time for that to happen, but this is the long haul. I would advise your friend to find a cheap place to swap the converter out so that he can keep the car. In 5 years, that car may be worth $3k.

    • I am not sure how detailed a MOT inspection is, but there are ways around a failing catalyst. If the catalyst is not plugged (and causing the car to run poorly) you’re looking at what in the USA on OBD2 is a catalyst efficiency code. The way to ‘solve’ that without replacing the catalyst is to take the post catalyst O2 sensor and put a low pass filter circuit between the O2 sensor and the ECU. The low pass filter is a very simple circuit and very small. Easily hidden in the wire harness. Also very cheap to make, pennies actually.

      Also the catalyst could be blamed if only what is wrong is the post catalyst O2 sensor.

      • To explain what the low pass filter is doing, what sets off the code is spikes in the O2 sensor signal. The low pass filter does not allow the spikes to pass through it. The catalyst is still working, just every so often it doesn’t work well enough. If that happens twice within a specified interval the code is set and the MIL comes on.

        • I had an old kia go into limp home mode ages ago. Cooked the cat. Money light came on which was an automatic fail in my commie home state that likes to obd scan cars yearly. Pulled the downstream sensor and jbwelded the sniffer end. Reinstalled the sensor and reset the confuser. No light. Works for quite a while until the jbweld burns off. Look up o2 spacer for a more permanent but obvious hack. Ran that scatbox for 100k until i got tired of patching all the salt damage.

  8. Thanks to you, I don’t look at anything past a pre ’15 JDM sports car (370z, Toyobaru, Pre-15 WRX/STI)

    Older cars, you address the issues, add fresh fluids and parts and bam, solid car!

    Engine/Transmission goes? Rebuild or swap a better one, cost would be less than a downpayment and financing, plus it’s more personal at that point.

    Again, $15k, buy a 5k Jeep, another $5k in fixing it up and use the remaining 5 for a roadtrip

    • “Again, $15k, buy a 5k Jeep, another $5k in fixing it up and use the remaining 5 for a roadtrip”

      Unfortunately, the sheep no longer believe in “stretching the dollar”. They prefer living comfortably in debt.

      • Sorry, accidentally clicked before I could add more

        You’re right, only other person I know who does that is my friend who builds civics and Jeeps, due to having no $$$$

        Friends looking to lease a CLA when I tell him get an e90 328xi (’07-11, with the inline 6, N52, not the problematic twin turbo N54), as he wants a classy German as a commuter (hear those are relative gems, replace the plastic engine parts with metal and they’ll last)

        At this rate, I got a better chance of winning the lotto than I do of him ever listening to me

  9. It’s all psychological. It’s all about reminding them all day long how they are destroying the climate. That was another reason they changed the name to CC. Lemmings read CO2 and global warming in the AM and forget about it until the evening. While they’re going to work, coming home or just running around,,, for those with weak minds,,, that engine shutting down and restarting is screaming CLIMATE CHANGE, CLIMATE CHANGE, CO2, GLOBAL WARMING.—– ” bad human, bad!”

    • Hi Ken,

      Your observation is excellent; hat tip, sir! I think you’re right; and not only is ASS a way to remind drivers about CC all the time, it is another means by which to make driving other-than-electric cars unpleasant. So as to “nudge” us into EVs.

      • That is precisely what I think ASS is for – to force us into electric cars. I unfortunately just bought a new car (because some moron drove into me and totaled my beautiful 2008 car). As I am driving my new car, it keeps shutting off the engine at stop lights and then jerking to a start when I hit the gas. How anyone could possibly tolerate driving like that is beyond me. I have never been so angry. Fortunately, there is an off switch for this ridiculous technology but you have to hit the button every time you get in the car. I can’t wait to get rid of this new car and get a nice old car that is still fun to drive.

        • Krista – what type of car are you driving? I bet I could design a circuit to do an end run around that switch to activate the system every time you are in the car. It likely involves wiring a relay or two that will signal the ASS to shut off. Of course, it will likely “void the warranty.”

          • I really appreciate the offer!! You guys are the best! Unfortunately, I probably have to hit the button every time for now since the car is a brand new Alfa Romeo that I am leasing and I am definitely not keeping it long term so messing with the car in any significant way probably isn’t worth it.

        • On the Ford system all that is required is a jumper wire behind the switch and it goes away forever. On a smarter system a timer circuit may be required to simulate a button press. So long as there is a button there is a way to automate the pressing of it.

        • Hi Krista,

          People often disagree with me, but on ASS the response has been universal. People really dislike it. But most people who haven’t been in a new car lately don’t even know about it. Like you, they buy a new car and then they find out about it. And are not happy.

          Note that ASS is not advertised. In fact it is hidden. You have to really look for info about ASS on every car manufacturer’s web site. They know ASS is not a selling point.

          Lately, I have been noticing that the off button for ASS has been quietly disappearing. When this system first began to appear, there was always a button – an obvious and easy to use one – to turn ASS off. But that button has been physically absent from almost all of the 2020 ASS-equipped new cars I have testy driven recently. You have to “scroll” through menus in the “settings” area of the LCD touchscreen and then you can turn it off. The intent seems to be to make it difficult to turn ASS off in the hopes you won’t.

          And the broader purpose, I think, is to make other-than-EVs annoying to drive, in order to make EVs (no ASS!) more appealing and to guilt-trip non-EV drivers by reminding them, at every stoplight, that they are “contributing to climate change” by not driving an EV.

          • Eric, I have read (but don’t know if it’s true) that these ASS-equipped cars have a switch that tells them when the hood is open so the engine will continue to run for diagnostic purposes. Supposedly if you disconnect the hood switch, ASS is disabled.

            For some vehicles there is also stuff like this:


            It all just makes me happy to be driving an ancient beater.

          • A person I know complained about ASS. Said when he went for a test drive the start / stop never actuated until the next day when they took it for a spin. He took it to the dealer and they explained it was ASS. He was told he apparently didn’t notice it during the test drive.

            Apparently the sales group knows ASS is disliked and so turn it off before the test drive and before you head home in your new car.

            Buyer beware….

            • That is EXACTLY what happened to me! There is ZERO chance that I didn’t notice the ASS on the test drive when it was so glaringly evident to me on the drive home! Oh, I’m going back to the dealership.

        • Krista,
          I had a similar “totaled” experience a couple of years ago with an ’02 4Runner I had owned since new and had planned to keep forever. Gone at the stroke of an adjuster’s pen.

          I was fortunate that I knew about ASS before shopping for a new vehicle. The salesman said the car had it, but it could be turned off.

          He was wrong. The model I bought did not have ASS at all! Yippee!

          As it turned out, I still got stuck with a car with direct injection and variable cylinder management (which thankfully, can be disabled).

          And I still mourn the loss of my ’02.

          Cars used to be about the freedom to go where you wanted, when you wanted. With a stick shift if you wanted (which I did).

          No airbags, no shoulder harnesses, no ASS, no driver’s “assist” suites, no distracting touch screens, and no television commercials showing Dad or Mommy sighing with relief that they didn’t carelessly back into a speeding semi trailer truck with their precious cargo on board.

  10. Great catch Eric. ASS is one thing I get pissed about. None of my families cars have it except a F150 that was defeated permanently with a paperclip.

      • No, on my F150, you have to take the switch off from the dash, a few minutes, then just jumper two wires in the back, forget witch wires, re-install the switch and it is permanently off. It would also work if I could have wedged something in the switch as well.
        Eric is now saying that they are removing actual switches and putting the ‘switch’ in the touchscreen menus, so it would be impossible to fool the computer without someones ‘defeat’ system as described a few posts above.

  11. “To minimize the possibility of catalytic converter damage: Do not shut off the engine or interrupt the ignition when the transmission is in gear and the vehicle is in motion.”

    Love it!

    Eric, once again you have exposed the idiocy of a federal agency run by tree huggers.

    • Naaaa,,, GW just gives the Agency the appearance of ‘protecting the moronic public’ when instituting these lame ideas. Also secures their pension you are funding. And keep in mind most of these — idea’s — are coming from the manufacturers. This stuff comes out as a option for awhile then the gov makes it mandatory.

      Manufacturers are making a fortune on these useless frills and corpgov gets the blame. Like Obamacare…. The Medical Industrial Complex writes the laws for congress critters. The ‘law’ gets passed and corpgov takes on the blame while you take it up the wazoo. Gun laws,,, same same. The proponents of these ‘laws’ know you will grumble BUT you will pay because of”it’s the law programming” and our gods in black robes have ordained it.

  12. Every rental I get that has that thing pissed me right the f()ck off. I can’t remember the car it was, but shutting the thing off wasn’t a dash button; I had to go into the “infotainment” system and shut it off EACH TIME! When I stopped at lights, I had to fiddle with the throttle to make sure the PIA didn’t kick in.
    I’ve said it before, but I’m going to go backwards with purchases, buying older and older cars because all these new ‘features’ suck. As you’ve discussed multiple times, it takes away from your driving ability and a lot of it is more distracting than the cars around you.