2005 A8 D3 4.2 (BFM) - Low MPG

[ainarssems]

Timing tools are not that expensive for 40V engine compared to 32V, I would definitely buy my own, after all I even bought tools for my 32V which are a lot more expensive. You can always sell them for not much less than you buy them for when you are done anyway.

Camshaft timing would effect fuel consumption a bit but should not be too much unless it's way out in which case inlet valves would meet pistons.

I have seen single front brake caliper sticking to cause fuel consumption to double, brake disc was glowing red in dark after drive. Did not feel it much driving, just felt like a bit down on power and needd to press accelerator a bit harder, also pulling a bit to side if you took hands off steering wheel.

So it could well be a combination of several issues on your car.