Audi A8 D3 Fuel Consumption

[Elisabet Schwartzkopf]

My80,000 mile 2.0TFSI Turbo Audi has lost a lot of performance but produces no check-engine-light (CEL) or codes. One month ago an independent garage looked at it and did $2200 of work including transmission fluid, air and fuel filters, new sparks etc...

When I got it back it was fixed, and boosting with a healthy sssh on acceleration from 2200 RPM, which lasted for about 6 days and then suddenly back to poor performance or worse, and no noise from the turbo except at 6000 when high pitched whistle/whine evident. Fuel economy seems really bad - about 15MPG.

Took it back to garage for smoke test, vac test etc. but still no CEL or codes. They say it's boosting at 7psi, but that they feel a lack in performance. I guess they used a physical gauge, but I don't know how or where they took that reading.

I can't read Manifold Absolute Pressure (MAP), sadly, because I suspect a leak. Don't know if it's missing, broken, not in this model car or what. update vag-com reads it fine, must be a problem with my software.

I wouldn't rule out a bad MAF so quickly - there was a generation of VW and AUDI MAFs that slowly went south without any indication from the ECU that they were doing so and IIRC the ECU managed to compensate for the dying MAF for a while.

The fact that the fuel trim it +5 (what unit is that, percent?) and not negative suggests to me that you get more air into the engine than is accounted for and the ECU is adding fuel to get the fuel ratio back to stoich.

For starters I'd pull the plugs and check if they look like the engine is running rich, lean or normal. That should give you at least a basic idea if the problem is upstream or downstream of the engine. Basically the idea is that if the plugs look like the engine is running really rich, you might have a problem with the O2 sensor(s), if they look like the engine is running normal there's a decent chance that the problem is upstream of the intake.

This means the problem is with a sticking solenoid in one of the turbo valves - either the wastegate or the diverter valves. The mechanic mentioned as we were running the test that this often unsticks solenoids, so I asked him to let it keep clicking for a whole minute.

The diverter valve was replaced by audi less than a year ago, so will still be under warranty, and given that I was getting boost (MAF records lots of air going in) I think that's the most likely candidate.

I previously had a 1.5litre Honda Civic Sport for 3 years (which I now wish I had kept, given the SOS fault and related software issues with the A3) which regularly achieved 55+ mpg on extra-urban trips and 30-35 mpg around town.

Hello, I have driven my car recently (35TFSI 150bhp s-tronic) and got over 46mpg on a short 13 mile trip. The delivery driver got over 50mpg from an 80 mile or so trip. As for the drive select button - I have no idea what it does as there is nothing on the car telling me about the different modes it may have (for reference I have the Sport model). Cheers, Dan

Just to add my car has done 6000 miles, so well run in. Car is running on 17" pirelli cinturato P7 tyres. Just now after a short 12 mile drive I have achieved 59mpg (deliberately driving as economical as I could). Cheers, Dan

Since I originally posted this topic, I managed to get just over 50mpg on one long motorway journey (London to Manchester and back) but normally in the South London suburbs I seem to average around 25mpg.

Sorry to hear of your dreadful experience and hope you can get your money back. I am having a few teething troubles too. The driver select button does nothing and there is no sat nav in the car I just bought. Hopefully these are just software/set-up issues. Did not realise the car does not have cd player in, apparently music can be downloaded and put on a stick thing lol. Good luck and I hope you get a full refund. Cheers, Dan.

Yes, it was an ex-demo (not entirely advertised correctly as the mileage was 20% higher than that quoted - naughty). Have tried pressing the drive select button several times now but with no luck. Sat nav is standard so possibly a subscription issue as you say. Cheers, Dan

Think I might be having the same problem you have, the SOS warning came on together with a yellow triangle with an exclamation mark in. Switched off car for an hour and it went, I guess something to ignore. Wonder if Audi can uninstall all this useless, unnecessary tech stuff ? A dacia sandero might be a better option as will come with very little tech (but possibly a cd player lol). Cheers, Dan

This is the problem, the more tech they cram into cars the more unreliable they become. Which is a shame as the engineering aspect of cars and mechanical components have come on leaps and bounds. But now being let down by electrics abd computers. Good news though you can still buy a new lada niva if you want something simple and less boring than a Dacia lol

If you are getting the SOS warning, then I would go back to the dealer with it if I were you. I have now had Audi finance come back to me and they have acknowledged my complaint and I expect to have the car taken back in a week or so. I have to wonder, what happens to these rejected cars, because mine is certainly not the only one - do they use them as demonstrators perhaps?

This a very common fault within the VAG group it seems. A fix is on the way hopefully by the end of the year according to some users on another BB. As for the drive select not working - turns out that is also another software issue that has had a fix out (only my vehicle must have missed the software update). The dealership is going to rectify some other faults soon so I will see how that gets on. Otherwise I do enjoy the car with its smooth ride and great economy (58mpg today on a 13 mile trip). Mine is an ex-demo btw. Cheers, Dan

I have had my 2020 model 1.0L petrol A3 (30 TFSI) for 11 months. It is manual transmission as I prefer to be in control. My usual run is semi-rural (Wallingford to Didcot 7 miles away, Wallingford to Reading 12 miles away or Reading to London Paddington station - if there isn't a train to get me home at night - 52 miles away).

Using E5 fuel, I regularly get over 50 mpg driving at road speeds without being "Captain Slow". However, right back from my army days in he Royal Corps of Transport, I was taught to drive well in my instructor expecting me to "make good progress but anticipate events up ahead early" avoiding unnecessary braking - I have had it up to 60 mpg. Running on E10 fuel, the mpg drops considerably - anything between 42 mpg and 48 mpg but I cannot, for the love of all things mechanical, get it up to 50 mpg.

As soon as I fill up with E5 fuel again, back up goes my mpg so I refute the government scientists' and the petrol companies' that you hardly notice any difference in consumption! You damned well do!

You use a bit more fuel if you have an automatic gearbox, if you use the cruise control or speed limiter or if you use the air con (and you should use it at least once a week, even in winter, to keep the system fresh and in good order).

My car goes in for service in a coupe of weeks ad there is an "Engine Management System Software Update" due, according to the My Audi App, so I hope that doesn't affect either performance or fuel economy adversely as I love my car as she is even if she is boring, plain white!

Many thanks for a very enlighten post.

It seems that increasing the ethanol content to 10% results in a weakened mixture, which can manifest itself as a lowering of performance, and an increased consumption.

Others may disagree and have better evidence than me that the consumption is not affected to any noticeable degree - it would be interested to hear of these experiences.

Your post was of particular interest to me, since my 3ltr non-Audi was 3/4 filled with E10 and this seems to be disappearing at a rate of knots greater than when last filled with E5. Very limited, and not very scientific experience, but I intend to return to E5 and see what happens.

Many thanks again for your post.

Does anyone know which brand gives the best fuel consumption?? For servicing, i know all will be expensive.. but is there a difference in cost b/w these 3?? (Generally, which will be more expensive in servicing?)

Difference between 8km/L vs 10km/L is less than $100 petrol bills assuming you travel 2000km a month. Why bother if you already driving a car that cost 1500-2000 times as much? Don't really see the rationale.

Car dimension has no impact on FC. instead, it would involve torque curve & vehicle weight. The weight of passenger has an impact on overall vehicle weight. Traffic condition & tyre pressure also play a part in FC. Lastly, if the vehicle travels like 1,000km/mth, what kind of saving we are looking at?

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