Fuel Ecenomy on Automatics - Advice Please

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BevC
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Fuel Ecenomy on Automatics - Advice Please

Post by BevC » Mon Oct 22, 2018 7:07 am

Apologies if this has been asked before. After 35 years of driving manual cars I finally took the plunge and went for an automatic, which I am starting to get used to. I know there is a facility to check your economy, but this can be quite distracting. I am trying to figure out the best way to drive an automatic - is it better to gently accelerate or to get to desired speed quickly to get the best fuel economy? Is it better to brake or decelerate by lifting before braking?
Corris Grey/Oyster Portfolio 180AWD


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BLZeebub
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by BLZeebub » Mon Oct 22, 2018 7:36 am

Anticipation is the key i find. My 180 diesel XE AWD is my first automatic and i've experimented since getting it with different ways of driving. My daily commute is about 16 miles each way on mostly decent B roads for 5-6 days a week and then the odd motorway blast. For the last 10+ years, in diesel Peugeot 406's, i averaged 47.1mpg over the year for pretty much the entire duration at an average 29mph.

The first month in the XE was booting it at pretty much every opportunity and having fun and mostly in Dynamic - that returned about 42mpg which was less than expected. For the second month i tried a different approach and used relatively gentle acceleration and declaration with minimal braking by reading the road more. That improved the month to the 48mpg mark.

The following month i tried a similar approach but in Eco mode which seems to have had a slight improvement in MPG but next to no difference in anything else so i will probably stick with that approach.

A few longish trips 'Ooop Norf' at 60-70 cruising speeds have seen a best of 63.1 over a 140 odd mile run with the same approach to reading the road and easing on'off and my daily commute even had a 59mpg on a particularly good day but i've also had a 33mpg on a particularly bad day.

I disable S/S for about 99% of the drives - usually at the first pull up when it's about to engage and i remember!

Things to bear in mind are that cold weather will have an effect and is noticeable in that the morning run is usually noticeably lower mpg that the run home with all else being equal as the warm up time is slower in the morning so i expect a drop off now we are heading towards winter. Also, if i need to pick up speed quickly then i usually tap the paddle to drop a gear or two. I tend to leave home around 6am to avoid traffic as that has a major effect as noted from a few trips into London and a couple getting stuck in the school run nightmare.

As i've noted before, i actually enjoy both the 'search for more economy' and the 'boot it and have fun' and if anything the daily approach means the 'boot it' runs have even more of a grin factor but that may just be me.

All figures are from the on board displays but i have been running to almost empty and filling to the brim and getting around 550 miles to 53 litres so i reckon they are not far off.

HTH

Cheers
Nat
MY17 All Black R-Sport 180D AWD with some gadgets. B-)


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PhilB
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by PhilB » Mon Oct 22, 2018 8:05 am

As above!
The main thing is smoothness.
Try and avoid heavy acceleration and braking.
The auto box is set up for economy in eco and to a big extent in normal so you will find it very keen to select a higher gear asap.
I wouldn't bother generally having the current mpg display at the bottom of the screen as it varies so much with acceleration etc but it can give some ideas if you are in the cruise on a motorway etc.
Plus in most cars in top gear on the motorway keeping it below 2000 rpm is the sweet spot for economy.
XE S 380, Storm grey Pics Black venoms/black pack, 18 ways, BSM, 40/20/40, ICTPro 380, parking pack, spare wheel.
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Indianajons
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by Indianajons » Mon Oct 22, 2018 8:37 am

I drive mine in D all the time, accelerate, cruise and brake no differently to all my previous manual cars and average around 55mpg with a computer generated best of 78.4 on a run
2017 MY tempest grey Portfolio 180D, folding mirrors, 14 way seats, memory pack, cold weather pack, 360 parking, wi-fi hotspot


capese21
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by capese21 » Mon Oct 22, 2018 10:49 am

Just drive it & enjoy it and let the MPG sort itself out. The difference will be negligible.


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Petercoll
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by Petercoll » Mon Oct 22, 2018 7:13 pm

The modern torque converter automatics like ours have less frictional losses than a manual clutch which loses energy through heat creation when you change gear. Automatics provide comfort and luxury by choosing gear changes for you. This alone drops fuel economy. Picking your own gear changes manually with the paddles will always improve fuel economy by 1-2 mpg, as told to me by the JLR technical boffins . In addition, sports selection on the rotary dial locks the gear box in manual, and enlarges the number gear you are in on the display in front of you which is helpful, but you always get a default setting to a lower gear if for instance you happen to slow down too much or stop. Oh , one last thing, for winter driving , manual changing can put a sudden jerk through to the wheels, promoting a skid. If manual is still preferred, engage highest gear possible at every available moment. This is where automatic is streets ahead of manual .
MY 18 XE 25t r-Sport , Corris Grey with rear privacy glass, 19 inch wheels, In Control Touch Pro, larger disc brakes, Adaptive Dynamics & split rear seats.


spritely
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by spritely » Mon Oct 22, 2018 9:29 pm

Indianajons wrote:
Mon Oct 22, 2018 8:37 am
I drive mine in D all the time, accelerate, cruise and brake no differently to all my previous manual cars and average around 55mpg with a computer generated best of 78.4 on a run
I have the same engine in my car - only done 1300 odd miles from new, but best I have managed so far is 48mpg. I am hoping that this will improve - as perhaps the engine is not fully loose yet? I mostly do shortish drives on a mix of fast ish A roads, and a small bit of town driving. I was hoping to break 50, but not so far. Perhaps I am expecting too much? I must admit to the occasional dip in to sports/dynamic mode - just for the sheer fun of it. but otherwise I drive it like Miss Daisy. :lol:
Corris Grey 180D R sport - loving it.


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Vespa
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by Vespa » Tue Oct 23, 2018 10:52 am

I suggest just driving it as you would a manual and let the cars brainbox work the gears for you. Mine is one of the first made and has a set of green to red indicators in the middle of the display (if required). The lighter your foot on the pedals the more green bars are showing and if the throttle is given the heavy foot they go to red bars in various degrees. I always drive in Dynamic and get upto 40's around town with a warm engine. With the engine cold I get around 28 ish on short journies. In winter diesel fuel gets a bit thicker and the engine takes longer than a petrol to warm up. On a long run around 60-65 mph I can get into the 60's mpg.
180 diesel XE R Sport, with many extras :D


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Madatter
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by Madatter » Tue Oct 23, 2018 12:50 pm

I drive a manual all day at work so tend to be a bit heavy footed in the jag and only get low 30s mpg but if I get a good run I can easily get into the 50s and motorway driving mid 60s. Unlike the wife who constantly gets high 40s to mid 50s. It's all in the driving.
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147daytona
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Re: Fuel Ecenomy on Automatics - Advice Please

Post by 147daytona » Tue Oct 23, 2018 1:34 pm

Petercoll wrote:
Mon Oct 22, 2018 7:13 pm
In addition, sports selection on the rotary dial locks the gear box in manual, and enlarges the number gear you are in on the display in front of you which is helpful, but you always get a default setting to a lower gear if for instance you happen to slow down too much or stop.
Not strictly true, selecting S on the gear selector doesn't in itself lock the gearbox in manual mode, only if you use the paddles does this happen.

I personally drive in S mode but let the box sort out the changes for me, it doesn't let the revs drop so low before changing down a gear compared to N mode.
MY17 240 R-Sport, IRR, Black Pack, Park Pack, Cold Climate Pack, 19" Twin 5 Spokes, Jet/Red Interior, 10 Way + Lumbar, Split Rear Seat, ICT Pro, Illuminated Tread Plates, Configurable Mood Lighting, Alloy Paddles & Pedals, Homelink, Spare Wheel.


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