Auto StartStop

[Gregs24]

Well I never, a Pom without a sense of humour. Whatever next?
I haven't the time, or inclination to argue with strangers on the interweb.
Don't read my posts. It'll be hard on me, but I'll get over it.
Cheerio.

No problem. Clearly you do not understand sarcasm, or are you still waiting for the kettle to boil to see how exciting it can be?

I will read what I want and comment as I see fit.

Don't waste your time responding, I know how much attention that kettle demands....

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[NegativeMultiplier]

That's impressive mileage for a 3:73 rear end. I'm leaving for home in the morning and plan to just set the cruise control and listen to music if the idiots and 18 wheelers going up hills in the inside lane will let me. Will report mpg back.

Indeed, though I virtually never see it. My current trip timer is reading 16.7 and that's surely going to be lower by the end of today.

 

[Frogdog1]

Home from 400 miles of half interstate and half two lane. Did not hold back on the throttle on the two lane part at all and it averaged right at 25 mpg. Not bad. Better than I expected. I could have gotten better but with this kind of power, I've learned I will go ahead and pass when someone is in the way. It is what it is. The car runs noticeable better now too.

 

[CzechMate]

Going back to the original topic — the start/stop system will destroy your engine. And it’s not the starter or the battery that’s the problem. It’s lubrication.


Engine wear is not prevented just by having oil. It’s prevented by having oil under pressure. Only then do the crankshaft journals and bearings float on a thin oil film. That’s hydrodynamic lubrication — the point where friction is minimal and everything spins safely.


After a start, even when the engine is warm, it takes several seconds for oil pressure to build. During those first 5–10 seconds, the engine runs in mixed friction. The surfaces of bearings and journals partially touch, partially slide on oil. This is exactly when most engine wear happens (probably 90%).


With start/stop, this cycle happens every time the car stops at a light. Repeatedly forcing the engine into mixed friction shortens the life of bearings and journals very quickly.


If you care about your Mustang, disable the start/stop system permanently. Your engine will last much longer.

Wach this video for more details:

 

[Gregs24]

Going back to the original topic — the start/stop system will destroy your engine. And it’s not the starter or the battery that’s the problem. It’s lubrication.


Engine wear is not prevented just by having oil. It’s prevented by having oil under pressure. Only then do the crankshaft journals and bearings float on a thin oil film. That’s hydrodynamic lubrication — the point where friction is minimal and everything spins safely.


After a start, even when the engine is warm, it takes several seconds for oil pressure to build. During those first 5–10 seconds, the engine runs in mixed friction. The surfaces of bearings and journals partially touch, partially slide on oil. This is exactly when most engine wear happens (probably 90%).


With start/stop, this cycle happens every time the car stops at a light. Repeatedly forcing the engine into mixed friction shortens the life of bearings and journals very quickly.


If you care about your Mustang, disable the start/stop system permanently. Your engine will last much longer.

Wach this video for more details:

There has been plenty of evidence presented in this thread as to why that is incorrect.

Do you really think engine designers are going to watch a Youtube video and go 'Jeez we never thought of that'!

90% of engine wear is on a COLD start, not a hot start.

There is very little additional wear from a hot stop start, indeed hybrid cars stop their engines way more than simple S/S systems fitted to a pure ICE vehicles. Cars such as the Prius which have a reputation for their engines lasting many hundreds of thousands of miles stop and start all the time when the vehicle is driving along.

 

[Starship Enterprise]

I disabled it in my preset just because it is stupid and annoying.

 

[CzechMate]

There has been plenty of evidence presented in this thread as to why that is incorrect.

Do you really think engine designers are going to watch a Youtube video and go 'Jeez we never thought of that'!

90% of engine wear is on a COLD start, not a hot start.

There is very little additional wear from a hot stop start, indeed hybrid cars stop their engines way more than simple S/S systems fitted to a pure ICE vehicles. Cars such as the Prius which have a reputation for their engines lasting many hundreds of thousands of miles stop and start all the time when the vehicle is driving along.

Cold starts? Sure, they cause most wear. But hot Start/Stop cycles repeated dozens of times a day are not the same thing. Bearings go through mixed friction every time the engine restarts, even when warm.


Hybrids like the Prius aren’t a fair comparison — their ICE doesn’t start at every stop. The electric motor can spin the engine before combustion, building oil pressure and lubricating bearings before the engine even fires. Some hybrids even have an electric oil pump to build up pressure before starting the engine.


Plus, in city driving, hybrids often move mostly in electric mode without starting the engine at all. They don’t need to cycle the ICE every time they move a few meters.


Everything in a Prius is engineered for this — unlike the 7th gen Mustang. Start/Stop is an afterthought. Thinking engineers design your engine with longevity as the prime directive in these ideologically driven, highly regulated markets — where dog eats dog and margins are thinner than a sheet of paper — is naive. They balance cost, emissions, and fuel economy, not giving your V8 a life-long spa treatment, especially when Start/Stop exists only to meet ridiculous emission regulations. Don’t get me wrong, the Coyote is a great engine — just not designed for Start/Stop.


And last thing: this thread provided no real evidence, only anecdotal claims from people who believe something. Just because someone’s oil analysis shows no wear after 5,000 miles does not prove anything. Prius longevity is not evidence either. If I missed any actual evidence, I’d be happy to reconsider.


I care about my engine — I disable Start/Stop. You do whatever you want.

 

[Gregs24]

Cold starts? Sure, they cause most wear. But hot Start/Stop cycles repeated dozens of times a day are not the same thing. Bearings go through mixed friction every time the engine restarts, even when warm.


Hybrids like the Prius aren’t a fair comparison — their ICE doesn’t start at every stop. The electric motor can spin the engine before combustion, building oil pressure and lubricating bearings before the engine even fires. Some hybrids even have an electric oil pump to build up pressure before starting the engine.


Plus, in city driving, hybrids often move mostly in electric mode without starting the engine at all. They don’t need to cycle the ICE every time they move a few meters.


Everything in a Prius is engineered for this — unlike the 7th gen Mustang. Start/Stop is an afterthought. Thinking engineers design your engine with longevity as the prime directive in these ideologically driven, highly regulated markets — where dog eats dog and margins are thinner than a sheet of paper — is naive. They balance cost, emissions, and fuel economy, not giving your V8 a life-long spa treatment, especially when Start/Stop exists only to meet ridiculous emission regulations. Don’t get me wrong, the Coyote is a great engine — just not designed for Start/Stop.


And last thing: this thread provided no real evidence, only anecdotal claims from people who believe something. Just because someone’s oil analysis shows no wear after 5,000 miles does not prove anything. Prius longevity is not evidence either. If I missed any actual evidence, I’d be happy to reconsider.


I care about my engine — I disable Start/Stop. You do whatever you want.

There are plenty of post on this thread with actual evidence.

I can assure you hybrids do not 'spin up their engine' before starting as that would actually significantly harm fuel consumption spinning an engine with no fuel going through it with mechanical drag. I drive a PHEV some of the time and on a long journey such as a motorway trip the engine will stop and start 100's of times, way more than the S/S on my Mustang. S/S has been around for 30 years or so now, millions of cars most of which were NOT scrapped because of engine failure.

If you just bolt S/S onto a 1990's engine then yes it will be a problem but that isn't the case, modern engines, ISG's starters and control systems work to overcome the 'obvious' problems.

Examples of evidence:

115925.pdf

Understanding stop/start automobile-engine design, Part 4: Mechanical wear issues - Power Electronic Tips

Review of engine journal bearing tribology in start-stop applications - ScienceDirect

 

[Bear376]

There is nothing pro or con that has been mentioned that would be considered substantiated evidence. The facts are, Ford has demonstrated to the Federal government that using this function reduces fuel usage under defined conditions. Anything other than that, meant that Ford would have to charge a penalty to buyers. I have start/stop on my F150 and after I got used to it, there are no issues. On my Mustang, it is even more seamless in operation. If you don't like it, there are ways to disable it.

 

[turtletim]

On the rare occasions when I forget to hit the off button, it only happens once. It's annoying. That's the one reason I don’t like it. Period.

 

[davidkwpg]

No, it isn't good for cars. You can read in thousands of places that the most wear in an engine occurs at start up. And, no, in my opinion, it doesn't improve gas mileage. I think car makers are desperate to meet EPA CAFE standards, thus this dumb feature.

I'm just used to starting my car and immediately hitting the start/stop delete button right next to the start button. Start/stop has to be the most asinine features to ever be put in a car.

BTW, I have a lifetime car average of 20.2 mpg. I've never re-set "Trip 2" since I got the car 3700 miles ago so it includes all kinds of driving. I don't think 20.2 is bad at all and my car isn't babied. It's seen it's share of speed and hard pedal pushing. FWIW. FD

mine really only kicks in if I am stopped at the lights and put it in neutral and pull up on the handbrake…..otherwise it never kicks in

 

[LouG]

Cold starts? Sure, they cause most wear. But hot Start/Stop cycles repeated dozens of times a day are not the same thing. Bearings go through mixed friction every time the engine restarts, even when warm.


Hybrids like the Prius aren’t a fair comparison — their ICE doesn’t start at every stop. The electric motor can spin the engine before combustion, building oil pressure and lubricating bearings before the engine even fires. Some hybrids even have an electric oil pump to build up pressure before starting the engine.


Plus, in city driving, hybrids often move mostly in electric mode without starting the engine at all. They don’t need to cycle the ICE every time they move a few meters.


Everything in a Prius is engineered for this — unlike the 7th gen Mustang. Start/Stop is an afterthought. Thinking engineers design your engine with longevity as the prime directive in these ideologically driven, highly regulated markets — where dog eats dog and margins are thinner than a sheet of paper — is naive. They balance cost, emissions, and fuel economy, not giving your V8 a life-long spa treatment, especially when Start/Stop exists only to meet ridiculous emission regulations. Don’t get me wrong, the Coyote is a great engine — just not designed for Start/Stop.


And last thing: this thread provided no real evidence, only anecdotal claims from people who believe something. Just because someone’s oil analysis shows no wear after 5,000 miles does not prove anything. Prius longevity is not evidence either. If I missed any actual evidence, I’d be happy to reconsider.


I care about my engine — I disable Start/Stop. You do whatever you want.

I think you're overlooking oil film strength. One of the big advances in oil technology. It allowed the use of thinner, more fuel efficient oils, and reduces wear on cold starts.
I do agree though, that ASS is the devils work.

 

[CzechMate]

I can assure you hybrids do not 'spin up their engine' before starting

That’s not correct — Toyota hybrids do pre-spin the ICE. MG1 (the smaller electric motor) brings the engine up to several hundred, sometimes around 800–1,000 rpm, before fuel and ignition begin. This pre-rotation lets the oil pump start building pressure and circulate oil before combustion, reducing wear during each start.


Also, the Prius engine isn’t a typical ICE — it’s an Atkinson-cycle design, with lower compression, lower RPM limits, and lighter internal loads. It rarely exceeds ~5,000 rpm and usually operates in a narrow efficiency band. Combined with the ability to move in EV mode and avoid unnecessary ICE starts, the hybrid system was designed from day one for frequent, gentle cycles — totally different from the crude Start/Stop systems slapped onto conventional engines just to meet emissions targets.

 

[Gregs24]

There is nothing pro or con that has been mentioned that would be considered substantiated evidence. The facts are, Ford has demonstrated to the Federal government that using this function reduces fuel usage under defined conditions. Anything other than that, meant that Ford would have to charge a penalty to buyers. I have start/stop on my F150 and after I got used to it, there are no issues. On my Mustang, it is even more seamless in operation. If you don't like it, there are ways to disable it.

Ford sell cars outside the US so it isn't just the Federal Government

 

[Gregs24]

That’s not correct — Toyota hybrids do pre-spin the ICE. MG1 (the smaller electric motor) brings the engine up to several hundred, sometimes around 800–1,000 rpm, before fuel and ignition begin. This pre-rotation lets the oil pump start building pressure and circulate oil before combustion, reducing wear during each start.


Also, the Prius engine isn’t a typical ICE — it’s an Atkinson-cycle design, with lower compression, lower RPM limits, and lighter internal loads. It rarely exceeds ~5,000 rpm and usually operates in a narrow efficiency band. Combined with the ability to move in EV mode and avoid unnecessary ICE starts, the hybrid system was designed from day one for frequent, gentle cycles — totally different from the crude Start/Stop systems slapped onto conventional engines just to meet emissions targets.

Actually it is far more clever than that with the Toyota (and other hybrids) including those with an ISG where the position the engine is at when it is off is pre-determined to make restart easier and consistent, unlike a start from a starter motor which just has to deal with what it finds from cold.

Are there loads of engines failing because of S/S? And before you answer remember pretty much every car in the world has some form of S/S that was made in the last 15 years.

I agree simple S/S systems as fitted to the Mustang are crude but they also stop the engine far less compared to a hybrid, maybe three to five times as often over the life of the vehicle depending on use, compared to hybrid 100s of times.

30 years of S/S systems means the modern cars work just fine with it.

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