TDI what engine is best ?
 

Ok so the D3 comes with a variation of tdi engines 3.0l 4.0l 4.2l
I would like to know wich one is best on fuel... Witch one is smoother quieter ect. Tuning options for both fuel consumption and better torque ect.. Im looking at a 4.2 tdi and also a3.0tdi

Thanks in advanced

Avoid the 4.0TDi as they tend to self destruct..

The 3.0 is more economical, but the 4.2 is awesome, can be easily mapped to 370-380hp and if you behave, you can get 40+mpg no problem.

i know the 3.0L tdi will easy see 40mpg on a run .. but i hear that the 4.2 will really struggle to even see 30mpg how do you get on with the 4.2 tdi ?

first thing would be a remap or tuning box and the rest would be left alone .. but i need real world figures . if the 4.2 would do 40mpg i would have that over the 3.0L tdi any day
but what is the truth behind the mpg ?

and is the LWB better on fuel dose it have longer ratio gear box like the petrol LWB dose and there for slightly better fuel consumption ?

http://dieseltuning.co.uk/audi-A8-diesel-tuning.html

interesting read

Agree. Avoid 4.0 competely.

The 3.0 is good. 50 mpg at a push, 45 ok, 40, easy, 37 is what I was averaging. A remap might help a little.

I cant speak for the economy of the A8 4.2, but the Q7 4.2 Tdi does around 5 mpg less than the 3.0 Tdi I find.

I can say however that the 4.2 Tdi is a truely stonking engine. the 3.0 is just fine, but the 4.2 is just staggering in comparison.

40% more cubic capacity, and 100% more turbo charger. It makes the Q7 feel 'nippy', which for a big bus is amazing, where the A8 is just incredble with it under the hood.

8 cylinders sounds so much smoother than 6 too, even chucking soot.

If you can afford to drop a little MPG, the 4.2 is the one to go for +++

The comparison you should be making is with the W12 for economy, and both will kill it dead :)

Cruising at the hideously boring speed of 65mph got me an average of 45ish from Dundee to nearly Glasgow, including a few roundabouts and hills. I'm averaging 30ish with a good bit of town driving and a heavy right foot with a cruise of around 80-85.

When you mash the loud pedal, it just goes, and goes, and goes, and keeps going until you wimp out. If you can find a good one, get the 4.2 over the 3.0, you'll regret the reduction in power especially when you're used to the W12.