What Is Auto Start-Stop?

What Is Auto Start-Stop?

Last Updated June 3, 2021 | Meghan Drummond

Auto start-stop shuts off your vehicle’s engine when idling, then automatically starts it again when your foot leaves the brake pedal. This helps save fuel you’d otherwise waste sitting in traffic. Unfortunately, it also annoys a lot of drivers who hate the feeling of their engine suddenly cutting off.

There's no denying auto start-stop's benefits in regards to fuel savings. On average, commuters waste 54 hours a year in traffic. That number is expected to rise in the future. That’s roughly $1,010 a year that the average person is using on fuel that’s wasted idling. While that’s a punch to the wallet for each of us individually, collectively the situation is even more dire. In 2017, a total of 3.8 billion gallons of fuel was lost to traffic.

But there are also some downsides to auto start-stop. People unused to the system are often startled by it. Many are also concerned with how it works and whether it might be damaging their vehicle (particularly the starter).

So, here’s everything you ever wanted to know about auto start-stop. From how it works to how to disable it if it’s not a good fit for you.

Silver S550 GT Mustang at gas station filling up

How Does Auto Start-Stop Work?

A common misconception with auto start-stop is that it's bad to shut the engine off and on so frequently. However, auto start-stop doesn’t completely turn off your vehicle and then cold start it.

When you first start your vehicle, it takes a while for the engine to warm up and the oil to lubricate the internal mechanisms. When auto start-stop is in use, the engine is already warm.

In many ways it’s like the difference between turning your computer off and putting it in sleep mode. While turning it back on from off would take time, waking it up from sleep is a lot faster.

When Is Auto Start-Stop Activated?

Auto start-stop is engaged when your vehicle has come to a stop and the brake is pressed. When these two things occur, the engine stops entirely and disengages the transmission, effectively shifting it to neutral. When you take your foot off of the brake, the engine is restarted with the transmission already in gear.

There are a few things that will prevent start-stop from activating. If you’re running your air conditioning or heater for example. Or if the engine hasn’t reached its ideal temperature.

In vehicles with a manual transmission, the car will need to be in neutral before it will stop the engine. When you press your clutch pedal, the engine will start back up.

Will Auto Start-Stop Damage Your Starter?

Any vehicle equipped with auto start-stop is also equipped with a more robust starter. The starters that come in an auto start-stop system use dual-layer, long life electric brushes. These brushes reduce the normal wear and tear of your starter by 90%. In other words, the starters are overbuilt to handle the demands of auto start-stop systems.

A conventional starter and a much larger start/stop system starter

Will Auto Start-Stop Shorten Your Engine’s Life?

No. For most people, auto start-stop will have no effect on engine life. For some, it may actually extend it. If you spend hours idling in congested streets, you’re likely damaging your engine. Idling can cause issues with spark plugs, and if the engine isn’t warm enough to fully combust fuel it can leave residue behind.

Auto start-stop is much better for engines than constant idling. And if most of your driving is on the highway, auto start-stop will have no effect on your vehicle.

Is Auto Start-Stop Dangerous in the Cold or Heat?

There are actually some very good reasons to leave your engine on at a stoplight. If it’s a hundred-degree day, then running the AC isn’t just about comfort, it’s about survival.

Different auto start-stop systems work differently with HVAC systems. Some use a beefed-up battery to operate these systems while the engine is off. Others kill the engine for a second and then start it right back up again. Either way, auto start-stop isn’t going to keep your heat or air conditioning from running when you need it.

How Much Gas Can You Save Using Auto Start-Stop?

How much gas you’ll save with an auto start-stop system depends on your driving patterns. If you’re a country roads kinda person, then you most likely won’t see any real savings. If you’re a driver plagued by red lights, stop-and-go traffic, and traffic jams, you’ll save a considerable amount. Some estimates say as high as 5% of your current gas usage.

What if You Can’t Steer or Brake?

Auto start-stop won't interfere with your ability to steer or brake when you need to. The engine restarts when your foot comes off the brake, so you should never be in motion while auto start-stop is on.

Is Auto Start-Stop a Good Feature?

Dashboard indicator light telling you the vehicle's auto start-stop system is on or off

Like most automotive features, the answer isn’t quite as simple as “yes, it’s good” or “no, it’s bad.” Individual driving scenarios will determine how useful, or annoying, this technology is for you.

When Is Auto Start-Stop Good?

If you spend a lot of time driving around town on errands or stuck in traffic, auto start-stop is a cool piece of technology that can save you a good chunk of money. Having an extra grand in your pocket is never a bad thing, and you’ll be saving your engine the stress of idling.

As auto start-stop tech improves, the annoying parts are being corrected. In many vehicles, the stop and start are much smoother now than they were in the past.

When Is Auto Start-Stop Bad?

Vehicles with auto start-stop installed always have a way to disable it as well. That’s because sometimes auto start-stop can be dangerous. If you frequently have to manage junctions and turns where you can’t spare a quarter-second without getting t-boned, it’s a good idea to turn it off.

Can You Permanently Disable Auto Start-Stop?

While every manufacturer allows you to temporarily disable auto start-stop, none give you the ability to permanently disable it. Fortunately, there are aftermarket autostop eliminators that will turn this feature off permanently.

If you’re one of the drivers who never benefits from auto start-stop, or you just can’t stand it, this is an easy modification to do. Check out this video to get an idea of what’s involved.

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What Is Auto Start-Stop?

Auto start-stop promises to save you money at the gas station. While that’s never a bad thing, there are some other parts of the technology that people have concerns about. Here’s what to know about auto start-stop and how it affects your car.