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

[Ratbert]

i'd love to see the same testing done for a diesel; i'm not assuming that idling consumption rates are the same between Gas and Diesel engines.

Yep, idling in a diesel should be up to something like 50% more efficient. That is, maybe 10-ish seconds before you hit the break even point?

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[SultanWild]

When the AUX battery dies, You gonna buy a new battery with all that savings

 

[Fatbob Frank]

Yep- instead of saving me money A.S.S. actually cost me $99...
Autostop Eliminator - Disable The Auto Start Stop Feature

 

[zouch]

idling is one half of the equation; the other half is Start-up...

being someone who tends to keep vehicles for a long time, the idea of shutting off and restarting a hot tubo-diesel for a few seconds just doesn't seem like it could ever save me enough in fuel to be worth the bother and the additional wear from startup. fortunately it's easy enough to turn ESS off.

Yep, idling in a diesel should be up to something like 50% more efficient. That is, maybe 10-ish seconds before you hit the break even point?

 

[driventoadventure]

idling is one half of the equation; the other half is Start-up...

being someone who tends to keep vehicles for a long time, the idea of shutting off and restarting a hot tubo-diesel for a few seconds just doesn't seem like it could ever save me enough in fuel to be worth the bother and the additional wear from startup. fortunately it's easy enough to turn ESS off.

The decades of real world implication so far demonstrate that engines and components properly engineered for the implementation seem to indicate that there's minimal at most detriment - considering in general that engines are lasting longer, with fewer failures and longer services intervals than ever - but that assumes that they're properly engineered which is a big assumption for a Jeep owner; and there have been no studies that I can find which actually test for start stop specifically.

 

[driventoadventure]

OK, So is it the general consensus that the ASS option is not worth using?

No. The only consensus is that there are as many emotions on ASS as there are asses.

 

[LSJKU]

Ok, so it looks like most the responses after SHTF starting on page 8 of this thread are done, and it may be safe to jump in with all my thoughts in one share. Yeah, right....

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.

Mr. Atomic, you are a way more talented and resourceful individual (ref the ER truck storage unit) than I, and I wish you the best. I do live part time in a rural area, so I get the parking in any spot. I don't look where I park for quick stops either. But I don't publicly revel in taking up an EV charging station spot when I do. That's just not right. I get it, you were attempting humor, but it's not humorous. I hate it when others sit at the pump doing other things when I need gas. The popular station with the best gas prices is usually very crowded in the central Texas area.

I do live near NW Houston the other part of the time as my wife is a "big city girl" from New Orleans and hates rural living. Nothing but us hillbillies, I guess, even though Gillespie and Kerr counties are two of the richest counties per-capita in Texas. And urban Houston is where my distaste for ESS mostly comes from. Rural people don't mind how long it takes you to accelerate from a stop; there are too many "Blue Hairs" that take longer, go 25mph everywhere, and make unexpected right hand turns from the left lane. Houston drivers, on the other hand, want to shoot you for a lot less.

I don't give a damn about how much gasoline ESS can save or how much pollution it can prevent. IMO both are negligible in the big picture. As pointed out in other shares, it's a hazard concern for me, having been hit from behind in Houston before (totaled our car). I too constantly watch whats going on behind me at red lights and want to be ready to react in a split second, or creep forward in an instant if I have to. It's a learned response.

I think even the split second delay when accelerating can be a hazard. Rolling the dice on a restart is scary.

I couldn't agree more. Even if the system gets you back going in under half a second, that's still time wasted in the event of an emergency.

My ass has been rear ended 3 times. I keep an eye on my rear view mirror like a hawk when I'm stopped at a red light these days

And I'm old school when it comes to cars (maybe too old school). Starting and stopping all the time used to be considered hard on any ICE car. The internal parts turning over with no oil pressure (rings, cam and crank bearings, lifters, etc), not to mention wearing out the main stuff involved (starter, battery, etc). Not good under any circumstances.

Then, there are the moments that want to make you poke your eyes out with a sharpened stick:

the auto start stop is harder on everything as it is. My mother in laws wagoneer died at a red light because the start stop was active and the battery was bad.

That has happened to me with another un-named brand vehicle (GM), although it was not in traffic or at a red light. Frustration was still there. I dislike GM's for a lot of other reasons though. Jeep Wick pointed out another good one, the dash status window encouraging shifting from 1st to 4th under normal acceleration on my Camaro:

I remember when they added this to the Camaro and Firebird. Eventually someone figured out a bypass.

Why the hell did my 2SS 1LE have this turned on from the factory? Drove me nuts. I didn't have a tuner to turn it off but finally figured out if you kept the pressure on the shifter, it would finally drop into second. It was kind of like missing a gear when shifting at normal acceleration speeds. So I "punched it" a lot. My Ford GT350 or Challenger Scat didn't have this hootenanny.

The ESS was not such a big deal in my 2018 JL with an auto tranny. I forgot to turn it off when I jumped in most the time as it was not my daily driver, but at the first stop, the JL usually reminded me to "push the button." Then again, the hot Texas climate, my liberal use of the a/c, or a charging battery prevented the ESS from doing its' thing a lot of the time.

When I bought my new 2025 JL 6-spd last February, it was truly a freaky deal to have the engine cut off automatically at a red light. I never, ever got used to waiting with the engine being off, and the second the red light turned green, pushing the clutch and dropping the trans into first, hoping the engine started, I didn't bog it, and it would go forward. I cringed and hesitated a lot, hoping I didn't get rear ended by the impatient driver behind me.

A few days after picking up the new JL, I received a new Tazer, ordered for other reasons. But the Tazer allowed me to "push the button" once and forget about ESS. The start/stop insanity is gone. Life with the std JL and Tazer, good once again. Thanks Tazer.

 

[LSJKU]

And I would be remiss at this point if I didn't give a shout out to the guys who worked in Irritable Bowel Syndrome (IBS-yes I know, I know) and South Park into the thread. I was channeling my inner Cartman over the IBS comments. Thanks for keeping it fun guys, Intended or not!

There's something wrong with that part of your electrical system. Have you checked your IBS?

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.

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

But I guess you 4xe guys don't have to bother with this ASS stuff, with your little hybrid e-torque thingy. I'm learning a lot I didn't know about the 4xe from this website, and the more I learn, the more I like the idea. Tons of torque on demand. I even saw this past weekend where the Indy cars are using a hybrid e-torque generator when needed. So there must be some legitimacy to this concept.

 

[Ratbert]

Apparently the Society of Automotive Engineers (SAE) tested multiple vehicles to quantify the effectiveness of these systems. Up to 26% improvement in fuel economy? That, of course, is in congested urban driving, but only about 20% of us live in rural areas.

https://saemobilus.sae.org/papers/auto-stop-start-fuel-consumption-benefits-2023-01-0346

 

[THAW]

Apparently the Society of Automotive Engineers (SAE) tested multiple vehicles to quantify the effectiveness of these systems. Up to 26% improvement in fuel economy? That, of course, is in congested urban driving, but only about 20% of us live in rural areas.

https://saemobilus.sae.org/papers/auto-stop-start-fuel-consumption-benefits-2023-01-0346

Same crap "study" mentioned in post #107. A light-duty truck has to be idled for 37.8% of the ~10 minute test to achieve the 26.4% improvement.

 

[Ratbert]

Same crap "study" mentioned in post #107. A light-duty truck has to be idled for 37.8% of the ~10 minute test to achieve the 26.4% improvement.

Oh, I didn't realize that was an SAE test. They're not exactly known for "crap studies" though, right?

 

[Jtphoto]

My 22 XR 3.6L etorque has just over 100k klm (60,000mi) still has the original factory battery and starter. I’ve never felt the need to turn off the ASS. My daughters 2018 3.6L traded in, in 2022 still had the original aux and main batteries. I think there is more at play here as per battery life then the ASS.

 

[THAW]

Oh, I didn't realize that was an SAE test. They're not exactly known for "crap studies" though, right?

It was a handful of short-duration tests done by the National Transportation Research Center using a dyno and EPA fuel economy protocols - not sure what the SAE has to do with it other than reprinting.

I put the word "study" in quotation marks because it was used earlier in the thread but is an overly generous descriptor for what was actually done, and the "crap" part is my way of referring to various organizations disingenuously reporting the single-vehicle, single-test max gain as the primary takeaway (were the minimum reported as the headline, the number would be 0.42%).

The bottom line is a relatively fuel-inefficient vehicle has to idle for 37.8% percent of operating time to have 20.8% worse fuel economy - somewhat unimpressive on it's face when presented in context, and not particularly meaningful as a metric for lifetime ASS use.

 

[Ratbert]

The bottom line is a relatively fuel-inefficient vehicle has to idle for 37.8% percent of operating time to have 20.8% worse fuel economy - somewhat unimpressive on it's face when presented in context, and not particularly meaningful as a metric for lifetime ASS use.

Earlier you said it was a 26.4% improvement, and now it's 20.8% worse?

It sounds like you have access to the test data. Mind sharing that link?

 

[THAW]

Earlier you said it was a 26.4% improvement, and now it's 20.8% worse?

It sounds like you have access to the test data. Mind sharing that link?

The link is in post #107.

The 26.4%/20.8% difference is just the way percentages work calculating ASS-less up or ASS down. Over 1.18 miles in about 10 minutes, the Ford Ranger got 14.9 mpg on ASS and 11.8 mpg ASS-less, a difference of 3.1 mpgs (the actual fuel difference was 0.018 gallons).

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