Automatic versus manual - fuel economy

What size tank do you have and what distance can you get from a full tank?
Don't mind what the computer shows when you fill it up, thats an estimate

chops018 wrote: »

I’ve a 2008 Audi, automatic, 2 litre diesel.

Full service done on it during the summer including gearbox oil change.

Usually when I fill up it comes up on the screen around 600km for the tank. Sometimes a little under or over.

My old 2007 A4 manual used to get 800-900km showing on a full tank.

I’ve heard manual A6’s around 2008 get 900-1000km showing on a full tank.

Are the older autos harder on juice than the manuals?

There might be just a smaller tank...

chops018 wrote: »

I am testing it properly now. Set the odometer thing back to 0 when I filled up. Half a tank gone and I’m on about 300km. So on track for around 600km. Maybe a bit more if I literally drove it into the reserve until it went no more, but I don’t like doing that, always fill up once the light comes on. So computer seems to be about right. Cost €72 to fill it to the brim from nearly empty.

The 2007 A4 was 2.0 TDI. This 2008 A6 is 2.0 TDI too. But automatic. The A4 definitely seemed more fuel efficient (and faster). Although the A4 was around €10 less to fill up if I remember correctly, that was only a few months ago as I’ve the A6 since the summer.

However, the A6 is much nicer the drive, the steering is lovely and I’m liking the automatic too! So I don’t mind the extra few quid on fuel. I was just wondering are older automatics a bit harder on fuel than their manual counterparts (or near enough) as I did hear the newer ones are better on fuel.

I've a 2014 A6 auto with a 65 litre fuel tank. When I fill it is usually shows around 900kms. I've my fuel calculated at about 7 litres per 100kms over the 3 years I've had it so that 900km is pretty accurate to a tank.

I think a 2008 with same size engine and same size car should be doing better than 600kms. At 72 euro for a fill you have a 65 litre fuel tank too I would imagine.

chops018 wrote: »

I thought it should be doing a bit better too. I don’t expect same efficiency as newer cars. But definitely thought a bit better than I’m currently getting. Anything that can be done?

I wouldn't expect a huge difference between your 08 and my 14.
I was getting around 600kms out of my petrol 2.5 bmw before moving to diesels and that was an 06. Although it was a 70 or 75 litre tank.

Are you doing mainly short runs with plenty of stops and starts? If I hit traffic with cold engine in commute my consumption soars too. Luckily I don't too often.
Id get a proper figure of what you are getting over a full tank or 2 and take note of type of driving before deciding theres a problem.

Also, take it for a spin resetting trip computer beforehand and see what it shows (although I don't fully trust trip computers in any cars)

My 2010 3 litre diesel does about 750/800km to a tank so there's definitely something up there I'd think.

chops018 wrote: »

Took it out there for a spin.

Showing 240km left in the tank (I know that’s an estimate) and the trip odometer has done 324km’s since I filled up.

The needle is at half way for the fuel gauge.

That’s not great. Anyone any ideas as the car is running great and no leaks under it or anything after being parked up. Full service in the summer and gearbox oil change.

It was actually scanned a few weeks ago too. No faults.

Have you checked your tyre pressure, checked for sticking calipers or worn bearings? Do you have the correct size tyres?

I'll be shot for this.. but have you tried using a strong injector cleaner for a few tanks.

Something like BG 244 or Archoil AR6400-D

Maybe your injectors aren't giving a proper spray pattern, and as a result you're getting poor mpg.

I've a 520d BMW and I'm getting 1200km with a 70L tank.

chops018 wrote: »

I might try that. Thanks. As I said, the car is driving absolute great in my opinion. So not sure why fuel economy is being crap.

I actually might get it through the NCT in the New Year and see if I can trade it in or a BMW 520D. Is yours automatic or manual?

8 speed Auto

colm_mcm wrote: »

It’s a bigger heavier car with a CVT gearbox.

That said, I would have expected more than 600km to a tank. The brother had a manual B8 A4 and I think it was doing more than 1000km to a tank.

Driving styles also influenced the mpg etc big time, also the weather this time of the year, heaters on etc, lights on longer all affect fuel economy

Is tank a unit of measurement now? :pac:

Old Autos used to be quite thirsty but the modern ones have actually been known to show a slight gain over a manual because you are in the optimum gear all the time

chops018 wrote: »

Yeah it's multitronic alright. Thing is, couple of months ago when I'd fill up the computer would usually come up at somewhere between 700 and 750 kms. I was happy enough with that as my old A4 manual was 800 to 900 kms. I thought bigger heavier car and fuel did go up a couple of cent so the fuel economy wasn't gonna be as good. But now it's down to 600 kms so that's not great.

I would be heavy enough on the pedal though and lately it's only been getting short journeys, plus colder weather and heaters blasting alongside using the lighter port for Bluetooth a lot lately. Wonder would all that make a difference.

I'd find I definitely use more diesel in the winter. I'd say the computer is just guessing what you'll get going on the previous tank. I don't put much faith in the on board computer tbh. I'll always crack the 1000km from the full tank, capacity is 66 litres, I normally fill when the light comes on so it usually takes between 60 and 64 litres to fill. Best I ever saw was 1400km on a trip around Kerry.

Important bit is how much fuel it takes to refill it vs what Kms you did.

chops018 wrote: »

I'm the same, once the light comes on that fuel is low I fill it up. How much is usually left once that light comes on?

Also, when I fill it up once the pump stops I usually stop filling there, but the tank can usually take a few more euro, so might be a few more kms there.

Since I filled it up last I've been tracking the kms. On just about 400kms now, computer is saying there's around 190km left. Gonna drive it on a small bit for after the light comes on this time.

According to my manual there's 7 litres left when the light comes on. They're very poor figures, I'd try the diesel additive. Unfortunately I think you're stuck with a thirsty beast. Any idea what the official figure should be?
Let us know what km's you have on the trip and how many litres it took to fill. I top mine off when it clicks, it usually takes about another €2.

I just filled up my 2014 A6 OP. See attachment. Its showing 860kms and thats based on recent driving, not sure how its calculated or how far back it takes into account. That's actually the lowest figure I have seen after a fill of diesel but I'm using less than a 65 litre tank a month these last 2 or 3 months so I'd say its basing it on the short trips with cold engine I've been doing. As you can see its 4.5 degrees according to the car and even has the cold weather warning on the dash.

For what it's worth I did a decent motorway spin and some mixed driving today and trip computer was showing 6.5 litres per 100kms which would equate to exactly 1000kms to a 65 litre tank if I repeated that type of driving. I wasn't particularly trying to be fuel efficient either. I have got is as low as 5.5 litres per 100kms before by deliberately driving economically and that would give me a theoretical range of 1200km, but I know I'll never do that over a full tank I'd drive myself nuts.

Assuming your tank is more or less same size which I expect it would be, as the A6 was always designed to be a long distance cruiser, your 600kms is looking very poor and might indicate a problem

Edit...yes I think tanks are the same size. Reread some earlier posts and you put 72 euro into yours, that's exactly what it took to fill mine today too.

Buddy Bubs wrote: »

I just filled up my 2014 A6 OP. See attachment. Its showing 860kms and thats based on recent driving, not sure how its calculated or how far back it takes into account. That's actually the lowest figure I have seen after a fill of diesel but I'm using less than a 65 litre tank a month these last 2 or 3 months so I'd say its basing it on the short trips with cold engine I've been doing. As you can see its 4.5 degrees according to the car and even has the cold weather warning on the dash.

For what it's worth I did a decent motorway spin and some mixed driving today and trip computer was showing 6.5 litres per 100kms which would equate to exactly 1000kms to a 65 litre tank if I repeated that type of driving. I wasn't particularly trying to be fuel efficient either. I have got is as low as 5.5 litres per 100kms before by deliberately driving economically and that would give me a theoretical range of 1200km, but I know I'll never do that over a full tank I'd drive myself nuts.

Assuming your tank is more or less same size which I expect it would be, as the A6 was always designed to be a long distance cruiser, your 600kms is looking very poor and might indicate a problem

Edit...yes I think tanks are the same size. Reread some earlier posts and you put 72 euro into yours, that's exactly what it took to fill mine today too.

How much per litre or how many litres did it take?

Buddy Bubs wrote: »

Took 60 litres @ 1.20 per litre.

7.3/100 or 38.7 mpg, wouldn't be great, it's what I was getting from my 1 litre dsg petrol Octavia. Maybe that's its best mpg for the size of car/ time of year.
Try a couple of bottles of this: https://www.skodapartsireland.ie/product/volkswagen-group-fuel-additive
it might help.

chops018 wrote: »

Ok. So I drove it on this evening till the fuel monitor said 20kms left. The trip meter was at 548km when I was going to fill up. Filled it up till I heard the click. €75, 63 litres, is what it took. Fuel monitor upon restart was at 700kms to empty. However, I drove it on for a few kms and it then went down to 590km to empty. Very odd.

There's a small dealer near me. They get in BMW's from BMW garages. He's a lovely 2008, 320d, 140,000 miles, 177bhp (I think that's what he said). He hasn't an ad up for it yet as he's putting it through NCT in next couple of weeks. There's a speed sensor gone, he connected it to an obd and showed me. Also, had a quick spin in it then and I was very impressed. However, I wanna go out tomorrow during the day and look at it. He said with the NCT on it will be €2600. He won't put up the ad if I give him deposit tomorrow and collect it in a couple of weeks when it's NCT'd. Do you think that is a good deal? Are the cars farmed out by main dealers to smaller dealers ok? The tax at only €280 a year is appealing too. My own is €710.

Annoying thing is they don't take trade in's at all. So I'd have hassle of selling mine. Surely I'd get €2000-2500 for my own?

548 km/65 lt = 11.5 lt/100 km. It is too much even for short trips imho. Unless longest trip in 548 km was 5km, it sounds like car has an issue causing excessive fuel consumption.

Have you checked previous poster's potential issues ? Low tyre pressure, sticky calipers, dirty air filter, faulty thermostats, etc