How Does Auto Start-Stop Work? Car FAQs

Did you know that cars equipped with auto start-stop systems are sometimes called microhybrids? Me neither, but the more you learn! And today, we’ll do even more of that, taking a look at the start-stop technology, which automatically shuts down and restarts the engine when the car comes to a stop to reduce fuel consumption. 

Coming up, we’ll check out:

• Exactly how does auto start-stop work?
  
• When was the technology first introduced and why?
  
• How much fuel can it save?
  
• If the system is bad for your car.
  
• How to disable it in your car and if you can make it permanent.

Enjoy the read!  

What is Auto Start-Stop? 

As mentioned in the previous paragraph, the auto start-stop is a system meant to save fuel by reducing the idle time of an internal combustion engine. According to some online sources, it was first introduced in a mass-produced car in the 70s by none other than Toyota – they put it in their 1974 Crown model, claiming a 10% gas saving. 

Others (like Car and Driver) suggest that the first production car to use auto start-stop was the Volkswagen Polo Formel E, which debuted in 1983. Regardless, it was around the 1970s and 1980s that we were graced with this technology. 

How Does Auto Start-Stop Work?

While the principle is simple—your car comes to a full stop, your engine shuts off, you lift the foot of the brake, it turns on—its reliable implementation is a bit more involved. After all, you don’t want the critical systems of your car to be deactivated at a busy junction. To support the auto start-stop, manufacturers introduce necessary changes to both engines (internally) and their accessories. 

This usually includes things like:

1. ECU programming adjustments – it’s not just a matter of adding one line of code that shuts the engine off when you stop. Apart from controlling the starter, the ECU monitors other conditions like the oil and catalytic converter temperatures, air conditioning, and battery charge. This is to prevent the auto start-stop from activating when your engine isn’t adequately lubricated or if restarting it would put too much stress on the battery. 
2. How the accessories are powered – instead of using a traditional serpentine belt, AC compressors or water pumps are run electrically. This allows you to enjoy the cool breeze even at a standstill and prevents your car from overheating. 
3. Special coating of crucial engine components – in some cars the crankshaft bearings have a polymer coating that acts as a dry lubrication, slowing down wear and tear. This is further reinforced by the use of special engine oil additives meant to improve low-temp surface protection in start-stop scenarios.
4. Reinforced starters and stronger batteries – starters on cars equipped with auto start-stop have to withstand more start-up cycles (duh!). So, they are obviously built stronger, with some of the newest vehicles including a separate 48V starter motor that also aids in getting the car moving from a standstill. With more crank-ups, there is also more energy consumed, which warrants bigger batteries. 

Please note that these are not universal to all car makers, but rather a list of examples. Some manufacturers may include all of these modifications in their cars, while others may use a combination of either. 

Regardless of the exact implementation though, this many start-up cycles makes one ask…

Is Auto Start-Stop Bad for Your Car?

No, the auto start-stop isn’t really bad for your car. That being said, while modern engines are designed around this system and usually reinforced against the stress caused by more frequent start-ups, there are a couple of caveats. 

Despite the special coating, beefed up starters and batteries, or oil additives, remember that your engine will be running more often with only adequate lubrication levels. Of course, the ECU won’t allow it to be turned off right after you start it, without warming it up for at least a bit. 

However, due to the start-stop systems’ primary goal, i.e., lowering emissions and fuel consumption, it won’t be warming up longer than absolutely necessary. This means engine oil temperatures of around 160°F (70°C), which is less than the ideal range of around 200°F (95°C), though not dangerous or damaging anymore.

In short: you shouldn’t worry about the longevity of your engine even when using the auto start-stop system. Its operation might—theoretically—marginally increase the wear and tear, but you’d only start noticing these effects after hundreds of thousands or even millions of miles. So you’re safe, don’t worry!

Is Auto Start-Stop Mandatory?

The auto start-stop system isn’t mandatory in the United States, although you’ll find it in most brand-new vehicles sold here nowadays. What’s the reason for it? Well, whenever a new car is introduced, governing bodies have to check it for the emissions and fuel consumption. Including this system makes it easier to achieve good results, which helps not only with bringing the car to the market, but also selling it (low MPG attracts buyers).

Additionally, some markets require its presence, so it’s much easier and more cost-effective for the car maker to have it implemented anyway, regardless of the destination. 

How Much Gas Does Auto Start-Stop Save?

Since its inception, there have been many scientific studies conducted to measure the effectiveness of the auto start-stop systems. Depending on the source and the vehicle type, it was demonstrated that it usually saves around 5–10% of fuel. 

This doesn’t seem like much, but let’s say you use $2,000–2,500 on fuel annually (so around the US average). At the end of the year, you’re looking at about $100–125 in savings, which can buy you and your significant other a nice dinner at that moderately fancy restaurant you love.

Is it worth it? You tell us after that trip to the Olive Garden ;)

How to Turn off Auto Start-Stop Permanently?

While you can temporarily deactivate your auto start-stop system until you turn off your engine and ignition, there aren’t many ways to do so permanently. For most modern vehicles, the only method of permanently deactivating it is with a dedicated auto start-stop eliminator device. We wouldn’t recommend using those unless you got it from a reputable manufacturer.

However! If you drive one of the BMW Group models, there is one simple and reliable way for permanently disabling this system – and you’re in the right place to get it…

How to Disable BMW Auto Start-Stop?

If you want to permanently disable this system in your car, you should definitely check out our BMW Start Stop Disable coding upgrade. After you buy it, our technician will reprogram your auto start-stop button to remember your last setting – so if you turn it off, it will stay turned off once you get back to your car. 

Everything happens during a quick coding session and the only thing you have to do is connect your PC to your BMW. You don’t need to install any “eliminator” devices, so your car stays basically fully OEM. 

A Useful Feature or an Eco Gimmick – Auto Start-Stop Summarized

As you can see, the auto start-stop system is not without its merit. In the long run, it can save you some money (around $100–125 a year) and it shouldn’t really affect your engine's longevity. However, no one will blame you if you find its operation annoying and want to deactivate it. Just remember that some start-stop eliminator devices might not be too reliable, so try to find one from a reputable seller or seek specialized deactivation coding (like ours for the BMWs).