Does Engine Idling Waste Fuel? (Start-Stop Technology) 

It would also be helpful to know how much wear and tear all this restarting adds to the engine, starter motor, etc.

its fun and games until the car doesnt start again edit: did not expect to see a war down in the comments

A note, accelerating slightly slower and coasting slightly more can also save +10% on mileage while also reducing wear on your engine

Let me answer some things as an automotive engineer. We’re in the day and age of planned obsolescence and EPA overreach. The start/stop system in general is designed to save the consumer money in the short term, but make the dealership techs money in the long run while appeasing the EPA. You will save money during the duration of the failure point, the starter’s life. Automotive companies are hoping that once the starter eventually goes out the average person is going to take their car to the dealership for a new starter. The service and labor fees will on average far surpass the fuel savings you got. This is why the RPM act and the right to repair or so important. They maintain the right of the consumer to be able to maintain and repair their own vehicles if they choose to do so. Cutting out the labor fees and just going off of what parts cost on average would actually net a positive savings for the consumer from auto start/stop technology. From their the consumer has to decide if repairing their vehicle themselves is worth their time. The manufacturer isn’t going to profit from the extra strain this system puts on your battery, but your battery will not last as long as it traditionally would depending on the amount of traffic in the area you live in. Traffic jams will be a massive strain on your car’s battery while average light to light traffic won’t be as bad. Everything is relative to your specific use and abuse of the system. Personally I feel that the savings up front aren’t worth the potential future lost time, so I turn it off (I happily repair and build my own vehicles. It’s why I’m in the field I’m in. I want to make things better for the hobbyist and consumer alike, plus I enjoy my work.) While I may not agree with it this is just the scope of the landscape.

+8% fuel -8% engine life Edit: We got WWIV in the replies before GTA 6

The starter motor: "I'm tired boss..."

All gangsta until the starter motor gives up in 5 years

Bruh most the time your car turns off as the light turns green 😂

I saved $2.65 on fuel, but then had a starter installed for $425.00 . What a deal

I prefer this system is hybrids because it’s a smooth transition of engine cutting off, accelerating again, then the engine cutting on again while I’m still in motion.

A friend of mine has been a trucker for his whole career. Decades ago, when diesel was cheap, they would let their trucks idle overnight in the winter to keep them warm. Used very little fuel and saved their starters over time.

Another aspect is in the intense traffic environment of big cities, where an extra second before you can drive away can mean trouble in several ways.

Now we need a study on wear and tear on the engine from multiple starts vs no starts, in between trips

So many drivers like to creep forward. They will come to a complete stop, shutting the engine off, only to start back up a second later when the driver creeps an inch forward. What a waste.

Now, do a bore test after 50k mile. Then you'll see the "real" cost of starting an engine over and over.

Never had a car new enough to have this technology.

Every time I'm in a car with my grandfather, he absolutely hates that function.

Start/Stop system on my older car: my hand on the key 😂

Driving habits play into this in a big way. I am a light braker, so i creep often, which causes my shut-off to go off and restart after a second. No fuel savings, extra wear, and increased fuel costs. To include huge R&E costs, more expensive starters, batteries, etc.... huge price tag increase for zero benefit to me and a ton of frustration. Especially because i dont live in a city or high traffic place.

The main thing I think I'd dislike about auto start-stop is the delay before I can go. My older car doesn't have this feature, but my newer car actually does. But it's also a plugin hybrid, so there is no delay. You're getting up to speed before the engine is even started, which is super cool.

Stop/start makes a lot more sense in a hybrid than it does in a normal gas engine. Reason being is many (not all) hybrids have an electric motor that's connected directly to the engine and can use this much more powerful electric motor to start the combustion engine rather than a traditional small high amperage starter. Also, being able to creep forward with the electric motors means the engine can stay off for longer making it much more reasonable as a solution.

The starter on my company delivery van only lasted 47800 miles with S/S on. And this was the original starter. Costed about $1500 to fix, glad i didn't have to pay for that !

Automotive engineer here. In layman's terms, the stop-start engines have different oiling systems, bearing material and an uprated starter assembly literally designed (along with the battery, engine tolerances and entire electrical system) For stop-start.

Starter: “I’m tired of this grandpa…” Auto start: WELL THAT’S TOO DAMN BAD

It would be interesting to see how the start-stop system affects the longevity of the engine and whether the costs incurred can be offset by the saved gasoline.

"now let's argue in the comments, shall we?" Now that's a man who knows how to use the algorithm right

It’s honestly really cool that that study even exists

I used to work as a mechanic for GM and had an occasion when taking my lunch break, I saw one of our customers up the street stuck at a set of traffic lights, upon approaching him and looking at the car, realised his clutch pedal sensor had failed so the engine stopped but didn’t pick up a signal to start again 😅

Ah yes the technology that only makes sense when the traffic is so bad you're better off walking.. useful stuff.

In Malaysia, most people deactivate the STOP IDLE function as the battery change cost more than the fuel by very large gap

The reason that start/stop is concerning to me is that it drastically increases the amount of time the engine spends with no oil pressure. Every time you start your engine it does at least a few revolutions before oil pressure comes up, and doing this 20+ times per drive instead of 1 has to have some kind of effect on bearing wear

Driving a relative's car a few times, I've found the stop/start feature to be dangerous when trying to cross or enter higher speed heavy traffic from a stop because it adds a delay in getting moving. I've had several close calls this way. I've also had close calls from the adaptive cruise and emergency braking systems reacting to things in other lanes that were no threat, nearly getting rear ended. It's "advancements" like this that are keeping me in my 11 year old, 18 mpg SUV for as long as I can keep it going. Please stop forcing these technologies down drivers' throats. Make these features opt-in instead of having to opt out every time the car is started. Until then, no way I'm buying a new vehicle. I'll happily drive my old gas guzzling, pollution emitting jalopy until it falls apart because at least I'm in control of all of it.

I bought a small device to permanently save what setting I have, and I just set it to off. The onboard counter told me I saved about $7 of gas in a year at the cost of over 150 extra ignition sequences.

Having the car shut off at a stop sign is infuriating.

The first thing I did when I got my 2020 CRV was disable the stop-start, it can be dangerous when trying to cross busy highways.

I had a 2021 Chevy Malibu as a rental for a few months and the system allowed the car to have mileage nearly as good as my 2014 Focus which was in the shop. It's a difference you can tell pretty clearly. What I found got in the way of it doing its job, though, was my favorite trick of putting the car into neutral so I don't have to ride the brake prevented the system from doing the job.

There is also a system that does this without using the starter. When it stops, it stops the crankshaft with the #1 cylinder just past top dead center with a fuel-air charge already in position. To start, it fires the plug and away it goes.

it’s less a about saving fuel more about getting past government emission restrictions

You’re saving some gas but hot engine oil is quite thin. When the engine shuts off, the oil pressure goes to zero and the oil drains out of the valve train and oil journals. Once started, the oil takes a bit of time to get pumped back into those areas. When this happens over and over, premature wear of cam lobes, piston rings, crank shaft bearings, etc. will result.

I’ve been using it for almost 2 years now, and it adds a significant amount to my MPG for sure.

I do a lot of f150 starter motors,stop start batteries on everything(mostly jeeps and other Chrysler products) and jeep wrangler starters. So yeh thanks!! The tech works for me !

Also a start/stop battery costs double,starter is probably more expensive too

It's super annoying in the ford edge we have at work. When the car shuts off at the lights you can hear the cabin fans turn themselves down and makes it hot and stuffy.

Arguing for fun, even though I’m also right ;) Start/stop in a vehicle without some form of electric drive is a safety hazard, with the safety risk increasing the degree of power lost. An electric drive with petrol range extender has no increased risk, while a drivetrain that simply has a slightly larger battery and starter that uses the starter to give the combined drive an extra 10-15HP carries the greatest risk. This risk window occurs when a stopped vehicle needs to make a sudden and un-telegraphed move, such as getting out of the way of a vehicle which has otherwise lost control. Instead of the driver releasing the brake and engaging the accelerator, or even having to engage the first gear in their manual transmission car, they also need to wait for the engine to start before the driver can initiate that same sequence. Since the fuel consumption of a dead driver is calculated as 0 miles / infinite fuel that is necessarily the worst fuel consumption rate possible (note my tongue placed firmly in my cheek). This also has the unfortunate, albeit rare, side effect of killing the driver, but Humanity must suffer for Humanity to survive 😂 P.S. it’s also a very disconcerting feeling this occur, as you try to accelerate with nothing happening at all, only for your car to suddenly leap forward as the engine finally engages the torque converter.

Everyone advertising how you can save fuel but nobody actually does the math: - how much you save per month/year - how much tear and wear it causes which will then backfire at your little saving Once you clear everything you'll find out that you'd be probably better off without the whole mechanism that makes your purchase price higher and service bills too. But hey, why bother. They say I can save fuel (or literally any other statement), so it has to be great!

The point of engine cut-off is not really to save fuel, but to reduce emissions.

When I had to have my 2016 f150 serviced, I was given a loaner 2018 with this feature. I wasn't told anything about it. I was stopped for a light, and while waiting to go, I needed to turn the wheels and couldn't. When I returned the truck, I told the dealer about it. That's when I first heard about it. I don't like it. It felt unsafe because of the slow response. Just a note some vehicles have an off switch for this feature. Problem is you have to push it every time you start the car.

From what I understand, the start/stop feature (my car has it) isn't to save _you_ fuel and money, but rather was a workaround, around the emmisions restrictions handed to car manufacturers.

Me getting 6.7mpg in my truck: Interesting ☕️

This is a handy feature on manual cars because you can control when it shuts off by using the clutch. This way it doesn’t shut off the engine every second you come to a stop like with automatics.

The stop/start delay causes a domino effect at traffic lights. If you have to wait for every car to restart, you'll never make it thru a traffic light in rush hour traffic.

The shortened battery life alone almost negates those savings.

My 06 v6 Accord Hybrid had that feature and it never bothered me. I drove that car to 285,000 miles before I traded it. Never a major problem with it.

What you have to think is that modern engines uses a very small amount of fuel when idling, so even tho the engine being stopped does save fuel after about 7 seconds (on a specific car the reasearch was based on), the amount of fuel being saved is very small. You are going to save a lot more fuel by cruising 5kph slower or just by being more smooth during acceleration. For reference, the GS1200 I ride gives the fuel consuption in litres/hour when I am at a stop. Idling, the engine uses something like 0.9L/hour. And note that it is a performance engine, 1170cc, 125hp, revs to 9k rpm, 1000rpm

I think there's another point to keep in mind, althought I think it is covered with these systems; but with older cars, when the engine stops the oil stops pumping into it, and if stays iddle more than needed, when you start it again the pistons are not fully lubricated, causing friction and damaging them

Abolish the EPA, they’re WAY overreacting and they fine companies ridiculous amounts for selling aftermarket products that make your engine MORE EFFICIENT

also if the vehicle have previously ran over a coupleof miles ,in the turbo charged engine scenario the turbo needs time to be cooled so idling will be a better option before turning of the engine or u may need to charge the complete turbo assembly

The alternator is fighting for its life after 30k miles😂

Yes, definitely consider the cost of starter replacement when using this option!

Fun fact! Engines with a start/stop system are actually built a bit beefier than their non start/stop counterpart. They have tougher engine parts bc the designers thought about engine life when adding a s/s system so ,no,youtube comments; A start/stop system will not dramatically shorten your engine’s lifespan. I’m saying this as someone who’s saved a lot of fuel over the past 8 years with my car having a start/stop system. Engine still looks, runs and feels fine at 200.000Km :)

Remember, guys, most engine wear happens at startups.

The problem with the auto start/stop is that it shuts off the engine as soon as you come to a complete stop, and restarts it as soon as you take your foot off the brake. So unless you’re in significant stop/go traffic, the engine is going to be off for only a second or two.

One thing I haven't seen mentioned is the wear and tear on the battery! A friend of mine did the stats over a couple of years and he said the money saved on fuel was minimal.

to anyone wondering about the starter, there is a short on this about the starter on start/stop car. forgot about the car etc but the starter was able to give out over 350,000 starts!!!!!!

What about wear components. Like lack of oil to the turbos. Is that something to consider. And do the pros outweigh the cons?

There are pros and cons just like anything in this world. Start/stop systems do save fuel, and that’s been proven by numerous entities at this point. It also promotes longer catalyst life when a car idles less and helps the DI engines get less carbon build up on the intake side of things. The negatives to start/stop technology are that in the summer your AC compressor stops running when the engine cuts off at a stop so you get intermittent warm air bursts if you’re at a long red light or in stopped traffic. There is also a lot more wear on your starter as well as the starter and ignition relays because they are being used significantly more than in a standard vehicle without start/stop technology. There really isn’t any difference between the starter and relay systems used on these newer vehicles compared to older models that don’t have stop/start, so instead of lasting ~150k+ you may only get an ~80-100k service life out of the same components.

I wonder how good it works in Arizona on summer at peak hours...🤔

Although it's been around a while now.. it still gets me to look every now and then when the Modern Car next to me, suddenly starts.. I daily a 68 Dodge Dart... Cheers from Southern California 🇺🇸

Starting is one of the most stressful moments for engines.

What sucks is when companies make it impossible to turn off without pressing that button every time you get in. Only way to permanently get rid of it on my dad's truck is to unplug the module but that also disables cruise control

I love the etorque on my Ram. Stops and starts are so smooth.

I shutter at the thought of our Honda, Pilot’s starter going out. Not just situational, like at a red light, but the cost to repair/replace.

My car would need to wait 2.5 seconds before the engine stop. Most of the time I just stop for 1-2 seconds and immediatelly take off. It just shut down to immediately start again. It's enerving!

These starters used in start/stop are special and cost about $400. If youre a self mechanic youll think "Oh, thats not so bad." But, the car counts how many times the engine has started and the check engine light sends a code at about 400,000 starts (about the time the starter will go out and your warranty will probably expire just in this timeframe too). To get the car to restart the count it takes more than just a fancy scan tool. Only dealerships [should] have the computer to restart the start count if you don't want the car dinging the check engine light. In conclusion, youll have to pay more than the $400 starter for the work to be done. Will the fuel savings over 400,000 starts save you over $400-$800 for a starter replacement?

it's all fun and games till that starter gives up on you

Click and Clack the Tappet brothers (CarTalk) actually talked about this one time. and i remember them saying that anything above 8seconds is when turning off the engine at a stop light is worth it. those guys were literally geniuses. and i miss them.

I wish there were some more tests done on long term reliability of this. Features like shutting the engine at a light and turning off cylinders definitely help the environment but won't matter when the car is in the junkyard.

Start/stop should be ILLEGAL. I almost got killed when my car stopped and couldn't restart in the middle of a highway intersection.

Constantly starting and stopping the engine would also contribute to oil contamination and poor cooling since you're not allowing the engine to reach operational temperature.

Something we can all agree on: Most of not all manufacturers are making motor vehicles/engines that break more frequently (atleast i think/hope we can all agree on this🤷‍♂️)

I really like the engine stop of my PHEV butbit also has a motor/generator, which is similar but beefier than a normal starter. When it restarts the drive motor give the car it's first little push to get moving and then the engine turns over and syncs without the tradional start up rev that you have when you turn a gas vehicle on. Since it's basically seamless it just sounds like when you push the oedal the engine was just really quiet andbthen started reving up as you push the pedal. In most gas start/stop vehicles you still seem to get the traditional start rev and then engage the gearing so there is lots of noise and then a slight delay before you move, which just seems exceptionally annoying for the tiny efficiency boost so in that case I would juat turn it off.

As an engineer I have often stated that all your theories must silently bow before empirical data. The referenced study is just that

Studies have shown that the wear out rate for the starter, the battery and the engine bearings is about 12% higher. To offset some of this extra wear, oil changes must be done more frequently. You don’t end up saving Diddy Squat with this technology, and when it breaks ( and it certainly will ) the repair costs are much higher for these types of starters. I programmed a disable for the start/ stop on my BMW 535i.

If you're so concern about saving fuel, put the car in neutral, turn off engine, get out of the car & push it along until traffic is clear then start the engine to continue your trip

I think like with every technology you have to understand how it works in order to really use it efficiently. Personally, I deactivated auto start/stop and trigger it manually whenever I know I'll be standing for a while, which works well for me.

"let's argue in the comments" reported for GASlighting

The car when it doesnt again:

In small towns where you are stopped for a few seconds it's actually really annoying. But bigger cities I totally get it.

Everyone's gangster until the car doesn't start up again😂

Ford tech here. The tech is pretty cool, but it creates a few issues, 1 obviously, your starter will go out much quicker, some manufacturers beef up the starter to compensate but not all. 2 people have been known to have their engine simply not kick back on, and they have to start it up again manually.

You wear out your starter and your battery hell of a lot faster too

That sure surprises me. I had figured more like 60 seconds. What about the fact that the engine turning off means the car takes longer to warm up on short trips and means that the fuel that seeps into the engine oil doesn't burn off.

everything in a car is about balance....start stop vehicles still use the same batteries, starters and alternators. You are simply shifting the cost of gas vs the cost of parts the manufactures do not use better parts and they wear faster due to the start/stop.

And all of the fuel savings ends up costing you:.. a replacement battery. Congrats😂

I'm not saying my car is old but I don't have stop-start technology. I have ”stop-why won't you restart" technology 😂

The key: What? dont mind me... YOU are your start stop.

Is it reliable?!

In mega cities with gridlock commutes its probably useful.

Stuck in traffic on a hot day without air-conditioning so you can save a couple of bucks? No thanks. Idle away.

That starter wear has gotta be crazy on these start stop deals.