I understand the reason for Jaguar to have the "intelligent start stop technology, designed to improve fuel efficiency..."
I appreciate that I don't have to pay a gas-guzzler tax for my 550 hp V8.

But now that I've pulled the plug to automatically disable the Start Stop Eco mode, I'm wondering if there's any real world data or study of how much real gas savings by having this feature? Yes, by shutting off the engine for a few seconds at stop lights will/may saving some gas, but any real world real data/study about how much real gas savings? ie: 0.1 gal per tank, 0.5, or 1.0 gal or whatever the real gas savings are? As I'm driving around in 100 degree weather with AC on, the engine stop & starts within 10 seconds to keep the AC on.

Also, my thoughts are that once the engine is warmed up & running efficiently, it's better to pay to use some gas, maybe cheaper than the wear & tear of stopping & starting the engine on the premature failure/replacement of batteries, starters, & other engine parts.

Does anyone know of real studies numbers, or it's just "you'll save some gas $$$"...

 

Put simply, it's all BS to satisfy Government dictats (read CAFE) and you will save next to nothing.
Maybe, just maybe, if you constantly drive in peak hour stop/start traffic with long periods of not moving you might save a few cents.
See here:

 

Obviously the cost or saving will depend on how and where you drive.

I counted the number of stops and approximate duration on a commute round trip to/from my office and home. It is a 2h trip consisting of town driving at either end with a motorway stretch and some hill climbing in-between. If I recall correctly I was stopped at lights about 15 times for an average of 45 seconds each time (some much longer, there is one set of lights that cycles every 2 minutes). The Eco stop/start activated each time. It rarely kicks in for normal traffic stop-start as the braking it much gentler when creeping in traffic. So for a 2h trip the engine was off for about 11.25 minutes which is 6%. I believe the generally-accepted rule is 5% for "extra urban" driving, so I am pretty close to that.

If I were to make that trip leaving the office at rush hour then my 1h return home usually takes about 1.5h with nose-to-tail crawling for about an hour to leave the town where my office is. On those drives I can sit at lights for a couple of changes before the forward traffic opens up. With stop/start I could probably hit 30% engine stopped for that half of the journey, but I use my XJ for those trips as it is more comfortable and it lacks the stop/start function.

Those figures are based on engine running vs engine off time though, and don't take into effect the difference in fuel use when idling vs when driving up steep hills. The fuel savings are at a time when the engine would be using the least fuel anyway. That is the purpose though - it is not designed to save the driver money (that is just how they sell it to drivers), it is designed to reduce the early urban deaths from road pollution which is a major issue worldwide.

I suspect that difference between time saved and fuel saved is why the car makers don't show you a separate figure at the end of each trip saying "You saved 2.5 litres of fuel for this trip". It's because it would almost always be 0.1 litres or similar so would reinforce the "why bother?" attitude.

I live in a small town with relatively little through-traffic and surrounded by miles of green fields and forests with just one main trunk road in and out and most other routes designed for horse carts (some of the roads even need mowing). The air quality at home is so good I can detect when someone on the other side of town lights a bonfire on a still day. When I visit a big city like London I can really struggle to breath, particularly when trying to sleep on a warm night. My eyes dry up and make wearing contact lenses really difficult as well. Beautiful sandstone buildings are black and grey from the soot. I would hate to live in a place so polluted. The fact that locals get used to it is quite alarming.

On the one hand I hate to think that in 15-20 years my cars will be undrivable through a combination of usage bans, taxation and in the longer term non-availability of fuel to run it, but on the other hand I won't miss the pollution from ICEs one bit.

In the UK we banned smoking in public places like pubs/bars/restaurants 11 years ago. As a non-smoker I used to struggle to go out anywhere without being forced to cough and rub my eyes constantly, and I would stink like an ashtray at the end of every day. Nowadays the smell of cigarette smoke is so rarely encountered that it actually takes me by surprise when I breath it. My kids generation may be the last to experience urban air pollution, and that is a good thing.

I can't find the reference but I recall reading that EU regulations mandate the stop-start function now, and will move to remove the driver opt out in due course so it will be active all of the time. At that time, at least in Europe, it would become a condition of roadworthiness like seatbelts, ABS and airbags, so disabling it would be an offence.

 

Edmunds tested it with an F-Type R and two other vehicles (Mini Cooper and BMW 328i). The results surprised me.

https://www.edmunds.com/car-reviews/...save-fuel.html

 

Jaguars have always kept an eye on fuel economy- going back to the etype.
Partly because its not a grand tourer if you have to stop every 200miles to refuel, as you do in most European cars with similar, even lesser engines.
My Jaguar with 510hp was gas guzzler exempt.
Etype gave 25mpg back then!

 

Thanks for the good watch & read above.
I've copied some points that I saw interesting:
"We used a modified version of our 106-mile suburban Orange County hybrid test loop, chopping out the longer stretches that lack stops. The resulting 80.4-mile stop-start test loop takes about three hours to complete.
starter motor has to be more robust
battery must have deep cycle capability that can endure more frequent draws from the starter.
engine's crankshaft and rod bearings need to have special low-friction coatings to handle the extra loads placed on them during frequent restarts
On a more practical note, you don't want the stereo, fan, lighting or wipers to shut down each time the engine winks off, and you don't want them to hiccup when it starts up again.The entire electrical system must be laid out in a different way.
Because the engine will be off, electric pumps are necessary to keep engine coolant circulating and to maintain hydraulic pressure in the transmission. The air-conditioning system may have additional humidity and temperature sensors to monitor the core temperature of the system during the shutdown period. If it looks as if the passengers might get too warm, the computer can abandon the shutdown cycle.
At local prices that returned $1.47 to our pocket.
Hot weather and the use of air-conditioning have a distinct negative effect. The biggest gains come in mild weather.
Stop-start is hard to ignore in a loud car like the Jaguar. This technology seems most ideally suited to cars that idle so quietly you barely know they're running. The F-Type gets away with it, though, because the snarling restart note of its powerful V8 is entertaining enough that you don't mind hearing it over and over."

For me, to save $1.47 over 3 hours (in CA gas prices, which is highest in the country) is not worth it.
The wear & tear on the extra robust engine parts (they said starting engines causes 80% of wear & tear...?) So how much will that cost over the years?

Finally, the 2 final points to me are:

"The biggest obstacle is mental: overcoming that sinking feeling that your engine just died.
It's no good if the driver becomes annoyed and seeks out the "off" button."

 

[QUOTE=xdave;1924683]
My kids generation may be the last to experience urban air pollution, and that is a good thing
.[/QUOTE
You are rather more optimistic than my assessment.

It's within the last twenty years that diesel engined cars became widely used, to allegedly save fuel costs and because they produce lower CO2 emissions, now that's a trend that likely to be reversed as its been realised that other pollution they produce in larger amounts than petrol are more harmful (NOx and particulates)

I don't consider EV to be pollution free until at least the electrical power to recharge doesn't primarily come from generation that burns, coal, oil or gas.

I agree with posters who believe fuel savings from auto start stop are variable and likely to be very small in most usage cases.

 

Thats exactly what my reaction was the first time the start/stop kicked in for me. I found that the reaction time of the system for restart had too much delay and was unnerving.

 

I think I reported it elsewhere, but my very first experience with stop/stop on the F-Type was so horrible it immediately convinced me to look for a way of disabling it permanently.
I reckon I had the car for about two minutes when I nosed it into a parking spot, but being my first ever drive of any F-Type I had no idea where the front of the car was and especially the "splitter" along the bottom, so I first stopped a good 2 feet (60 cm) back from the concrete gutter/barrier, only to have the damn car cut out on me! WTF! It then became a frustrating game of creeping up bit by bit with the engine going off/on/off/on/off/on/off, I reckon it took me a good two minutes to get fully and properly parked! Although I eventually figured out the "eco" button I decided then and there the stop/start had to go, I researched this forum the minute I got home and found how to do it and disabled the stop/start permanently that afternoon. Never regretted doing that for a single second ever since.

 

 

Obviously I don't have a crystal ball, but I based the 15-20 years on a few observations:
1) EVs and ultra low emission/capture are now a common, proven technology.
2) Regulation. Many European cities are banning ICEs in various forms from 2030, with restrictions already in place in some. More regulation will follow.
3) The average life of a car built today is now running at 15 years, so by then almost all of the cars currently on the roads today will have been recycled. The worst polluters are pre-Euro 5 vehicles which have average 12 year life spans so will almost all be dead by 2020.
4) Taxation.
5) Linked to (4), commercial fleet managers are replacing their vehicles with ULE ones thanks to generous capital tax reliefs making them cheaper to aquire than other vehicles.

Plus I'm 'only' mid-thirties so my kids generation is just entering pre-school and won't be raisng their own until the mid-late 2030s.

I found the dead stop in my F-Type to be quite unnerving for the first few months I drove it. My automatic reaction was to grab for the gear stick thinking I'd stalled the engine when pulling up to the lights. At times I am still aware of adjacent drivers/passengers looking over thinking I've stalled it. With time though I got used to it, and how to control it with braking pressure. The only thing I still find confusing is the way it shuts the car down if you undo your seatbelt while it has auto stopped. Because it is not something I do very often it still surprises me and takes me a second or so to realise what has happened. It is almost as annoying as the way it puts it into park automatically when you open the door to check alignment when reversing.

I wonder if Oz opened the door to check? That would shut the engine off, requiring a manual restart (not automatic), which could be repeated again and again.

 

Dave, now that you mentioned it, I may have opened the door!
Either that or I didn't realise that simply lifting off the brake would restart the engine (in theory anyway) so maybe I manually re-started the car each time it stopped?
I simply can't remember the exact details any more, it was such a horrible experience I suspect I erased it from my memory!
It doesn't really matter as even if I had figured it all out that first time I still would have permanently disabled the system pretty soon as I would have tired very quickly from having to remember to hit the eco button every time I started the car.

 

 

So what's the scientific study/data that shows the wear % on hot starts?
It can't be 0, since gravity does effect lubricants' coatings, even for 30 - 60 seconds off...