How much fuel does ASS (Auto Start Stop) save?

[Flip]

I didn't buy a jeep for fuel efficiency. I'm not saying ASS doesn't conserve fuel, its just not for this old dog.

Stay thirsty my friends.

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[THAW]

You know there is good data in the DoE and EPA studies which found the benefit can be a 25% increase in fuel economy from stop-start tech alone. Of course, those studies have been ripped down from those websites because, well...you know why. They don't support the current narrative. But those studies still exist, and the data was sound.

Here's the study. The ~25% mpg improvement figure is based on the single biggest outlier datum (resulting from a simulation of a light truck traveling 1.18 miles over 10 minutes in NYC traffic).

 

[Aonarch]

S/S does indeed save fuel, especially in heavy red light prone city driving.

That being said, it was primarily designed to cheat the EPA city MPG testing. This is done as roughly ~34% of the test is spent idling. The system needed to be automatic before the EPA would certify it as legit, so here we are.

What the engineers failed to realize is the wear and tear it would put on batteries. They thought about the starter, at least. Most heavy S/S users end up replacing their batteries every 2 years at most. Very few make it 3 years. Compare that to a conventional system where a battery can last 5-7 on average. The additional maintenance cost most likely outweighs any fuel savings, especially now that you're paying for two batteries. If you're paying someone else to install them for you I don't think it's possible to even break even there. There's also the increased chance of being stranded from a dead battery no-start.

This also led to the hilariously incompetent clutch situation on the manual JLs. Had to be light enough for S/S to function, and ended up being weak garbage as a result. I wonder how much cheaper it would've been to pay EPA fines instead of releasing 3 different recalls for clutch failures.

This. 100% designed for EPA tests and not actual consumer benefit. This is why the new admin doesn't like them. Everyone knows it's a scam.

 

[2nd 392]

I didn't buy a jeep for fuel efficiency. I'm not saying ASS doesn't conserve fuel, its just not for this old dog.

Stay thirsty my friends.

Love the reference my friend

On S/S- everything has risk/reward, tolerance depends on your individual use case, your use case odds ?

 

[LHSmith]

What savings? The minute amount you save on fuel will never pay for the extra battery and other components required!
Not to mention the ware and tare on the engine components restarting the engine over and over again.

 

[NWJeepr]

Here's the study. The ~25% mpg improvement figure is based on the single biggest outlier datum (resulting from a simulation of a light truck traveling 1.18 miles over 10 minutes in NYC traffic).

Sounds like a very real use case.

Everything else can be assumed to be in-between, which I'd say isn't ignorable.

I'm remembering back when I was a kid, and a 2000 Chevy S10 blazer, which is about the size of a Mini Cooper these days, would get about 15mpg. You could get a little higher in lockup in 4th gear on the highway. It was a wheezing 190hp out of 4.3L of bobtailed small block chevy.

Things have come a very long way since then.

 

[BXFXJeep]

Curious to know if the ASS causes oil dilution issues in the regular 2.0.

The 2.0 in the 4xe in certain situations seems to have issues because the engine does not get up to temperature with all that extended Stop|Start business.

 

[aeonixx1001]

Thats great if you drive primarily in stop and go city traffic.
Now, what about the rest of us that do primarily highway driving and seldom come to a stop (as compared to city driving). We are hauling around an extra bit of weight and obviously a more complex system with next to no benefit.
And while my driving style tends to get me the best fuel economy possible the day I become that concerned about fuel mileage is the day I start walking everywhere.

I found it was actually worse on gas mileage around town. Making brief stop and go at stop lights is the most gas consuming thing on earth. Thats my story and Im sticken to it. I disabled that shit so fast your head would spin. What an annoying feature for a gas powered vehicle.

 

[Ratbert]

I found it was actually worse on gas mileage around town. Making brief stop and go at stop lights is the most gas consuming thing on earth. Thats my story and Im sticken to it. I disabled that shit so fast your head would spin. What an annoying feature for a gas powered vehicle.

After watching the video, what's your theory on why it seems to get worse gas mileage around town with ASS enabled?

 

[THAW]

Sounds like a very real use case.

It's "like a very real use case" that's intentionally designed to not represent overall "benefit... in fuel economy from stop-start tech". The fact is, that particular test shows a 26.4% improvement in mpg requires idling a Ford Ranger for 37.8% of the test period.

It's clearly not a "good" study with "sound" data; the authors chose 4 relatively inefficient vehicles for unscientific reasons ("The use of these particular vehicles was highly opportunistic."), and inexplicably didn't put 2 of the vehicles through one of the 3 tests. It also looks to me like they sloppily inverted table data/labels, but maybe I'm missing something. In any case, it's a somewhat interesting experiment, but concluding from it that ASS-tech can improve fuel efficiency by 25% is a poor way to summarize it.

 

[NWJeepr]

It's "like a very real use case" that's intentionally designed to not represent overall "benefit... in fuel economy from stop-start tech". The fact is, that particular test shows a 26.4% improvement in mpg requires idling a Ford Ranger for 37.8% of the test period.

It's clearly not a "good" study with "sound" data; the authors chose 4 relatively inefficient vehicles for unscientific reasons ("The use of these particular vehicles was highly opportunistic."), and inexplicably didn't put 2 of the vehicles through one of the 3 tests. It also looks to me like they sloppily inverted table data/labels, but maybe I'm missing something. In any case, it's a somewhat interesting experiment, but concluding from it that ASS-tech can improve fuel efficiency by 25% is a poor way to summarize it.

You'll see from the summary/conclusions that "Consumers with auto stop-start-equipped vehicles can save fuel and money by leaving the system engaged, particularly in congested settings where idling is common."

Based on their tables, the more ASS engages, the higher the fuel savings.

The most popular vehicles in the US are full-size pickups so I find their vehicle choices (a midsize SUV, a minivan, a small pickup, and a midsize crossover) to actually under-represent reality, so it's possible larger and less efficient vehicles could stand to save even more.

I don't actually (personally) like stop/start systems, but I'm not going to discredit a valid study that says there are savings. On a fleet average that adds up to a LOT of fuel and emissions over years of use.

 

[Grey24Rubi]

Am I the only one who is channeling their inner Eric Cartman from South Park with the whole ASS saving gas topic?

I figured with all this talk about ASS it was just a matter of time before someone brought up IBS. I've seen the commercials about IBS, yikes, having problems with your IBS away from home doesn't sound like fun to me.

 

[Kristian]

My 2.0 E-Torque works seamlessly in ASS mode, but I always turn it off anyway. I pretty much always have my gauges (off road pages) on display, and I just can't stand seeing the oil pressure dropping to zero just to get pumped back up on restart over and over again in stop and go traffic. That can't be a good thing.

Also, what do we know about emissions when an ASS system cycles off and on. I know that cold start is the peak of emissions from an ICE, but what about emissions from warm engines repeatedly cycling off and on in stop and go?

 

[Atomic-Mouse]

I love parking my 392 in an EV charging station parking spot, it makes me smile every time. You have to cherish little things in life.

 

[HK1s]

https://www.jlwranglerforums.com/fo...op-really-make-no-sense-monetary-wise.126659/

I have monitored fuel rate at idle, it isn't much. all data is in the post.

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