MPG In A2 Diesel / Servicing etc. (Yes I'm new!)

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The 1.4 diesel doesn't seem that much more economical than the petrol when start/stop running is the main type of driving. I have been keeping a few records of my petrol 1.4 SE consumption and have achieved the following results (based on working out the MPG between fill-ups) 39.2, 39.9, 36.5, 45.0, 39.7. The best MPG of 45.0 was on my work trip of 20 miles on the motorway in rush hour traffic. The other results were recorded on an alternative route through the centre of Manchester during rush hour on a 12 mile trip. All trips were carried out in the dire Mancunian weather with air-con on about 50% of the time (heat), lights (it was usually dark), and the odd period of demisting first thing on a cold morning. Maybe the fact that the engine reaches full operating temperature helps the average fuel economy, but I'm usually spending most of my time stuck in traffic, or waiting at traffic lights.



Tino
Dolphin Grey 1.4 SE
 
My figures were measured with the DIS. But I just calculated the consumption for my last tank: it was 0.3 l/100km more than the DIS' calculation, which really seems to be a bit optimistic.

Martin
 
Tino,

From where I stand I totally agree. You quote 12 mile trips which I might regard as somewhat long in that the engine by then has had a chance of warming up, but if we consider a true short trip to only be say 2 miles (in heavy traffic) then I would be extremely surprised if there were any differences at all between petrol or diesel models – never mind 55mpg. At worst I got around 30/32mpg in my A2 petrol (on school run type trips), and in my diesel Golf I get at worst around 33mpg – so where is the wonderment of diesel in these extreme circumstances ? If it exists I sure haven’t experienced it.

Regards
John Disdale
 
Martin,

Much to my surprise I have through other forums been made aware that many Yank’s are equally obsessed with fuel consumption, however they take a step in the other direction to the point of arguing that unless a venting modification is carried out to the fuel tank it is not possible to accurately calculate fuel consumption based upon basic refills at the pumps. This I am given to understand is all because the exact maximum level on filling to the brim can vary – with auto shut off petrol pumps behaving differently, all of which can allegedly make a difference of over a gallon of fuel.

I suppose this is why when manufacturers carry out a fuel consumption test they use a 1 gallon can as the fuel tank.

Regards
John Disdale
 
Craig the average service here in PORTUGAL cost about
98 euros + vat 19% ....the oil costs about 73.40 about 4 litres - oil long life service.
Regards Tiago
1.4 tdi -silver

TCasaca
 
Two points:

1. Don't have DIS, so use tank refills to assess mpg. Agree that can lead to inaccuracies (owing to differing refill levels) on a tank-by-tank basis, but averaged over a number of tanks, will yield very accurate mpg figures. With 22 tanks of diesel, my range is from 62 mpg down to 52mpg, averaging at 56.6 (as mentioned earlier.)

2. Do not have A/C, but find that in current cold periods, switching ECON back on (on standard heating) on cold days - as it automatically switches off at temps below 5 deg C - boosts/saves around 4-5 mpg (notwithstanding innacuracies above).

Crawfster
Amulet Red, Open Sky 1.4 TDI SE
 
Purely for the record I never turn my climate control system off in the belief that its pointless paying a lot of money for a good feature and then not making full use of it.

The general subject of fuel consumption has been covered numerous times in the past, however I have to confess that only since having an onboard computer have I become far more aware of the “tricks” that can help improve consumption. My observations are hardly unique when they have been said before, but I know that if I want the “ultimate” in consumption then I need to do the following:

1/ Change up gear at the first opportunity.
2/ Don’t change down through the gearbox when approaching red traffic lights or at the end of a road junction, but put the car into neutral and roll the distance.
3/ On driving down hills or decent inclines, again put the car intro neutral gear (funnily enough this sometimes makes the car actually go faster).
4/ If you want to get the best reading from the DIS then go on a run starting off with a warm engine. Unfortunately I have few opportunities to do this, but it does make a difference especially in cold weather.

Regards
John Disdale
 
quote:2/ Don’t change down through the gearbox when approaching red traffic lights or at the end of a road junction, but put the car into neutral and roll the distance.
Click to expand...

Since owning the A2, and adopting this driving style as described by John, I have learnt two things;
1) You can roll a long way after changing into neutral. Usually to the frustration of the drivers behind me - [}:)]
2) Slowing down so early makes no difference as you always catch the traffic up when approaching roundabouts. I now cant understand why seemingly everyone drives as fast as they can between one traffic jam and the next. [?]

Kaine



A2 1.4Tdi SE | black | red leather | Concert | Open Sky | A2OC Stickers x2
 
Sorry JD, but i disagree with you on points 2 and 3. Putting the car in neutral won't SAVE fuel, it will COST fuel. All modern engines stop the fuelconsumption the moment you lift the accelerator (while leaving the clutch in position); the throttle will be shut that very moment. Putting the gearbox in neutral still takes fuel. That the car is going faster when it's in neutral is because there is no direct connection anymore between the gearbox and the engine. The engine does not slow down the car. Even if you should save some fuel, it'll cost you money because you will have to use the carbrakes even more.

Apart from this all, putting the car in neutral can be dangerous too. I don't know if some of you have had some extra training apart from the normal driving lessons to get your driver's license, but one of the first things you learn there is that you always need to choose the right gear for the situation you're in. If it's getting dangerous, mostly there won't be enough time to change the gearbox from neutral in the right gear, and you won't be able to react in the right way.

My conclusion is that putting the car in neutral is not saving any money and can be dangerous....


Regards,

JanF

2001 1.4 Petrol Exclusive
Cobalt Blue Metallic
 
JanF,

Well yes of course you make some points, but from your own words consider the following. You have stated that the moment you lift off the gas pedal the amount of fuel being used is the absolute minimum – so how can putting the car in neutral and not using the gas pedal use MORE fuel ? Moreover as I see it the moment a car is in high gear a “drag” factor automatically exists, and I say this in itself burns more fuel relative to freewheeling. Indeed so often when going into neutral it has an effect similar to taking the handbrake off, so it must be an efficient way of progressing down a road.

If you “freewheel” I do not see an automatic link that doing so means having to use the brakes more, thus wearing them out. Indeed I can think of plenty of instances where freewheeling down a hill/decline does not involve having to touch the brakes at all – so there is no wear factor to remotely consider.

In terms of “freewheeling” being dangerous perhaps it is, but so is driving on the road, especially at high speed. For sure I would argue that I am safer freewheeling up to a set of traffic lights at 30mph than doing 150mph down the motorway in top gear (which has been my style in past years).

Your comments about being in better control when you are in gear is a stance that I have contended all my life, so this is very difficult to argue with. All I can say is that “freewheeling” should only be carried out in situations where it is safe to do so, and there are thousands of these. In terms of freewheeling and not being able to shift into the right gear if a dangerous situation demands this, then all I can say is that I sincerely believe I can move from neutral into say 3rd faster than you could change down from say 5th to 3rd.

I enjoy a bit of controversy, but please do remember my tips were based on obtaining the ultimate in fuel consumption, and were not tips on winning a “driver of the year” award.

Regards
John Disdale
 
Sorry JD, but this dicussion is not yours. Scrap your Golf and buy an 1.2tdi. This car will teach you how to save fuel.

Regards
Christian
 
John,
an idling engine still consumes fuel - about a litre an hour.
Lifting your foot off the accelerator will stop fuel injection
altogether - fuel consumption 0. While these differences are very
small, it may amount to a few mpg...
Another word on engine braking vs. using the pedals: Using
the engine to brake wears the engine down much faster. I never do it,
I fully intend to pass the 300.000 -km mark with my 1.4 TDi. Check back in 6 years or so...

Werner Huysegoms
 
Christian,

Instead of you making totally daft comments like “this discussion is not yours” why not contribute with a bit more spirit and add what “tricks” you use for obtaining the best in fuel consumption.

Regards
John Disdale
 
Werner,

Putting aside engine braking your comments on fuel consumption clearly support those made by “JanF” so I have to conclude that I am wrong. What obviously I have failed to grasp is the difference between fuel consumption between an idling engine burning fuel (which is logical) to the alternative of a moving car in gear which is using zero fuel because there is no pressure on the gas pedal. This I still do not understand when I believed you needed some fuel to fire the pistons up and down. I thought the only time NO fuel was being used was when the ignition was switched off.

In accepting your knowledge that an idling engine uses say one litre of fuel per hour, I am trying to envisage a comparison test where 2 cars are placed at the top of a very long downwards gradient – say 50 miles long. Test Car 1 drives in gear for a few hundred yards and then cruises the remainder of the journey in neutral, which it does for 1 hour. The end result then is that the car has used 1 litre of fuel. Now test Car 2 sets out on the test and after a few hundred yards is in fifth gear, but with no pressure on the gas pedal the car travels the same distance as Test Car 1 – but it uses no fuel at all over the journey. This I still struggle to understand. Can you make me wiser ?

I cannot but help recalling a particular very long road gradient which I have experimented on for fun on numerous occasions. A situation might well exist where at the top of the gradient the DIS is displaying an average reading of say 45mpg, but if kept in top gear with no pressure on the gas pedal the reading at the bottom of the slope is 46mpg – however if the car is put into neutral then at the bottom of the slope the reading will likely be 47mpg. If this is NOT the case in reality, then presumably you are saying that the DIS is not working accurately when the car is in neutral. Is that correct, or am I missing something ?

Anyway I do hope that I am not seen as the only nutcase on the forum who believes that “freewheeling” is an efficient means of covering a distance.

Regards
John Disdale
 
Hi JD,

I used to freewheel, particularly when coming up to lights.
Back in March I did some Rospa advanced driver training. One of several criticisms of my driving was too much coasting, and changing down through the box to slow down; also too much brake dabbing.
The technique they preach is to use the acclerator to slow initially, then brake gently. When you have reached the required speed, change gear to match. Only take the car out of gear once stopped, and then only if you are likely to be stopped for more than about 5 seconds.

Possibly not as economical as freewheeling, but much safer if you need to pull away.

MartinW
 
Virtually all recent injected motors (D and P) make use of overrun cutoff to enhance economy.
Find a steep hill put it in 4th and release the gas pedal. In a diesel you almost stop petrols notice a definite decelleration.

icon_smile_cool.gif
 
Maersk,

Its not your use of the English language which is confusing me, but more my interpretation, so could you please confirm the following. Do I understand your account to mean that if you are in 4th gear (diesel engine) at the top of a steep decline, then if the accelerator is not used the car becomes almost stationary ? If this is so then it logically follows that under such circumstances the accelerator MUST be used in order to make some respectable progress ? Again if this is the case then the only way a true comparison on consumption can be made is with “Car 1” freewheeling, in competition with “Car 2” slightly accelerating. Surely if I interpret this correctly then “freewheeling” has to be the winner on consumption, when it MUST use less fuel than any other situation involving pressing on the gas pedal.

Oh what a laugh.

I have mentioned it in the past but if you go into neutral gear in a Quattro it creates an effect like throwing an anchor out the back. It’s most uncanny.

Regards
John Disdale
 
You can use freewheeling to increase the fuel consumption and you can use it to reduce the fuel consumption.

If you are going down a steep decline, the use of freewheeling increases fuel consumption because fuel is needed to keep the engine running, while if the engine is driven by the car absolutely no fuel will be used (this can easily be heard with a cold diesel engine, the sound gets much more smooth).

On the other hand, if you are going down a very slight decline, you might need to press the accelerator just to keep your speed. In this case freewheeling can reduce the consumption.


Martin
 
Martin is quite correct. The old SAAB 96s used to have a freewheel built in. On the two stroke 's' it made little difference as there was virtually no engine brake. Built in freewheel devices disappeared in the 70's except for the freewheel hubs on some of our 4x4 bretheren from Japan which were not automatic and youhad to get out in the mud and 'switch them off' if you got stuck.
Actualy engine pumping losses are greater in the petrol engine because of the throttle, which of course a diesel does not have.
The vehicle will slow on its descent. If you concentrate hard (depending on vehicle) you can discern the point at which fuel is reintroduced to the cylinders. Mostly this is very smooth but on some engines BMWs for instance there is a minor jolt (no that is too strong) but you get the picture. it re introduces fuel at about 15 mph dependent on manufacturers setting. The cut off is only on the overrun.
If you are a freewheeler JD you are a certifiable maniac and should be banned from the roads!

icon_smile_cool.gif
 
Maersk,

If I come freewheeling past you at 120mph with the dog sitting on my lap whilst I eat a box of chicken Tikka, then at least you will be able to explain to your passenger that you know the maniac. Thankfully though I have always known my driving limitations to the point of appreciating everyone else on the road is better than me.

Regards
John Disdale
 
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