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Discussion Starter · #1 ·
Hi all,

On my dashboard's digital screen, the MPG calculator (above the fuel range monitor) is constantly going up and down.

Its almost as if it doesn't have a clue, one second it will say 44, then the next 99 and so forth, rendering it completely useless.

Does this happen to anyone else?

FYI my car is a 64 plate 1.4T Excite.

Any help would be appreciated.
 

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I haven't got my car yet, but my Ibiza has this instantaneous reading and then another average reading.
 

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This isn't the 'true' MPG over a time... this turbo courtesy car does the same, it's more of a "CURRENTLY YOU'RE DOING 60MPG" then it changes based on the driving you're doing, it doesn't do it over distance like the other options on the car. If you're idle-auto start/stop it automatically climbs to 99MPG, if you want the true MPG I believe you have to set it on the trip settings as I believe the one above the fuel literally, as I've said is a "right this second you're doing 40mpg" then put your foot down "20mpg" then take it off "80mpg". Don't think you could keep track/log with this at all
 

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Yep, the instantaneous mpg will move up and down erratically as that is the whole point - it shows you every second what your engine is using. It is really useful to teach you to drive very economically. Mine hardly moves because I can constantly adjust my throttle in line with changing road inclines and traffic conditions. Once you get the hang of it, it can be become fun and a challenge to keep it steady.

For a more accurate and steady mpg you need to use the trips. After filling your tank to the brim, reset the trip. The as you burn off fuel the trip will show a more accurate average mpg over the tank. Ideally you need to do a couple of hundred miles before the average mpg gets accurate. If you keep resetting it and only do say 50 miles then it will be very inaccurate.
 

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I normally just reset my trip when I fill up. Have never reset trip 2 I don't think. Can the average mpg be reset separately with the Corsa?
 

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You have two trip counters each with their own mpg calculator, and another instant mpg calculator. I reset trip 1 every time I refuel, that gives me the mpg for the duration of the refuel. Trip 2 I never reset, that gives me the overall mpg since new. The instant mpg calculator varies from anything like 13mpg up to 99mpg, and that depends on which gear you're in, how fast you're accelerating, speed etc.
 

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Discussion Starter · #8 ·
mud4fun said:
Yep, the instantaneous mpg will move up and down erratically as that is the whole point - it shows you every second what your engine is using. It is really useful to teach you to drive very economically. Mine hardly moves because I can constantly adjust my throttle in line with changing road inclines and traffic conditions. Once you get the hang of it, it can be become fun and a challenge to keep it steady.

For a more accurate and steady mpg you need to use the trips. After filling your tank to the brim, reset the trip. The as you burn off fuel the trip will show a more accurate average mpg over the tank. Ideally you need to do a couple of hundred miles before the average mpg gets accurate. If you keep resetting it and only do say 50 miles then it will be very inaccurate.
Thanks for the heads up.

I see what you mean about the trip computer being the best way of recording MPG over time.

I often drive on a long flat stretch of 40mph in 5th or 6th gear, very steady (IMO) on the throttle and it still jumps around.

Guess I need to put a bit of effort into getting my driving style in tune for better fuel economy.
 

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I use trip1 for whole tank mpg/mileage and trip2 for individual journeys when I need to claim back travel expenses.

On a flat section of motorway my instant mpg stays pretty stable but will drop rapidly if I floor it or if I go up an incline. It is really useful because I have found that on some steep inclines on the motorway the car will happily pull up in 6th in cruise control. However mpg drops to 20's whereas if I drop to 5th I can maintain 40-50mpg uphill. It is worth watching for this as the 1.4T doesn't show any of the normal signs of labouring due to having a lot of torque in the mid range but the mpg takes a serious hit.

Some systems allow you to configure the sampling interval to get a more steady reading. Not sure the Corsa has that feature.
 

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It's amazing how much the instantaneous reading changes with just a slight less pressure on the throttle. I see cars whiz by obviously they don't have this reading.
 

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Skippy said:
It's amazing how much the instantaneous reading changes with just a slight less pressure on the throttle. I see cars whiz by obviously they don't have this reading.
It's not really that amazing tbh...

It simply adjusts the MPG based on how much fuel is going in. More you press, lower it goes.
 

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Yeah and I quite often get just 5mpg when I'm flooring it up a hill in my 1.4T...... ;-) I'm glad I never had one of these gauges on my 4.6 litre V8 Defender!!!!
 

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Mine actually went to 0.6 mpg (not 0.6 gal/h), when I floored it up a steep hill. I was a bit worried :lol:
 

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You lot are shifting it. On the level can save anywhere tween 5 and 20mpg with slight slight less heavy R.foot on the level with no noticeable loss in speed with the 1.0T 113 bhp.
 

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Skippy, my 1.4T manages 75mpg on the flat. This trip I managed a few months back, it is 80% motorway with the rest rural lanes and A roads. Note that the 72mpg was recorded over an 80 mile journey! (including lots of hills)

Car Speedometer Gauge Automotive design Personal luxury car


However we weren't talking about the flat. As can be seen I'm more than capable of driving economically but maintaining speed up a hill is always going to drink fuel and the instant mpg screen often drops to silly readings even with my careful driving.

My 1.4T has averaged 52mpg over 12K miles, it would have been closer to 60mpg but my wife was using the car alot in town. I will be interested to see what your 1.0T averages over similar distance.

I opted for the 1.4T because I found the lack of torque on the 1.0T on my test drive meant it couldn't pull tall gearing up inclines as well as the 1.4T so I reckoned the bigger engine would give the better real world mpg. Sadly not too many 1.0T's on fuelly so we can't see how well they are performing and not that many screen shots of trips showing better mpg than my 1.4T so I'm quite happy with my decision.
 

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420 mile round trip fully laden via motorway and town, talking average of 52mpg with air con.
Town driving brings it down to 44mpg ave.
 

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Skippy said:
420 mile round trip fully laden via motorway and town, talking average of 52mpg with air con.
Town driving brings it down to 44mpg ave.
Is that 52mpg on the trip? My fuelly figures are lower than the trip because the trip is not accurate, it generally overreads by anything from 3-13%.

Your figures are slightly lower than mine, my 1.4T does about 54mpg actual (56-58 on trip) on a 400 mile trip with whole family on board plus luggage but your figures are pretty damn good though :) They will improve as the mileage increases too.

Remember though that at the time I ordered my car back in January the 1.0T was £700 more than the 1.4T so the 1.0T would have to be getting significantly better mpg to negate the extra cost. Mind you I would have still opted for 1.4T to be honest as it is the more powerful engine.
 

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Where I live is very hilly in places so I opted for the 1.4T in the end. We have no motorways here, just a short stretch of dual carriageway, but a lot of the roads are winding and very steep in places. Current car is 1.2TSI and I have had over 60mpg over an 8 mile trip a couple of times. I test drove both the 1.2, 1.4 and 1.4T and opted for the latter as the 1.4 felt a bit gutless on one of the smaller hills. Hoping I will have made the right choice when I collect her at the end of the week.
 

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Didn't you try the 1.0T Leachie? I'm sure you'll be as delighted with the 1.4T as me but I still think that on very short journeys the 1.0T would have the edge as it should warm up quicker. Over my 130 mile commutes warm up time makes no difference so 1.4T suits me fine. I would have been interested to hear what you thought of the 1.0T though.
 

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I never did try it in the end. Only 1.0T they had was in an Adam that was inside the showroom. I would have wanted the 115ps version which would have pushed the price up too high.
 
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