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

How To Double Clutch Shift With A Manual Transmission

Engine start-stop is a technology designed to reduce fuel consumption, by shutting off the engine at stop-lights. But does this tech actually do anything? Obviously, an idling engine uses fuel, while an engine that’s off does not. But restarting that engine does use fuel. So which one has more of an impact? Well a study published in SAE tested exactly this, as well as real world test drives to see the impact. The results are surprising!

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[owengoodspeed]

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

[tychozzyx]

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

[robertpsotka]

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

[johnny_b]

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

[TeiwazTheGoat]

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.

[sentinelofchrist]

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

[FreedomAndLibertyGuy]

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.

[markcondrey]

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.

[Zage]

its fun and games until the car doesnt start again

edit: did not expect to see a war down in the comments

[DenisClan]

+8% fuel
-8% engine life

Edit: We got WWIV in the replies before GTA 6

[LilSerg]

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

[ZootyZoFo]

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.

[turtlemotonation]

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.

[anderotanerkask]

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

[jensalan]

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.

[utubeman]

I work selling alternators and starters- and we’ve found that permanent magnet gear reduction (PMGR) style start-stop starters tend to end up going through life much quicker.

The trade-off here is that you’d need to replace the starter- which aftermarket for these kinds range from anywhere in the low $70’s to the high $160’s.

Personally, any brand using an offset gear reduction (OSGR) is good. They have good power, and the gears underneath the Drive End Housing are basically fit into place, so it’s really hard for these to break. My favorite is Denso OSGR. Them starters are the best imo. Good torque always

[Rundumsfliegen]

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

[looped]

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 !

[johnm]

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.

[nickacelvn]

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.