A6 1.9 TDI Fuel Consumption

UK2004

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Have the above 2004 model, 130BHP, had issues with fuel consumption and had coolant temp sensor and thermostat replaced, seem to do the trick. Then again fuel consumption went really bad. It's now plunged even further. Getting just over 100 miles for £20 when that would of got 160 before and 200 before the problems all started. Any suggestions? Is it possible oxygen sensor needs changing. Mileage about to hit 160,000 so due cambelt change and wondering whether it's worth doing? Presume a change of two front tyres could not cause such drastic fuel consumption change. Also started to make bit of a shaky rough noise when starting in temperatures under 6 degrees.
 
Seized caliper? Wheel alignement? Engine shagged? Turbo on the way out? Leak in the charge pipe ducting?
 
Thank you for the reply, would any of those cause such a drastic change in consumption?

Also if this helps, it suddenly the other day got 150 for £20 then today 100 miles for £20 with similar driving style, can this help point to what the issue may be.

Just had the cambelt changed.
 
If the timing was off it could improve.

Impacts upon fuel economy result mainly from excessive fuelling or drag/frictional forces placing a greater load on the engine than usual.

The cam lobes being worn would not help. The pd engines are more prone to this than the earlier non pd engines. This is denoted by a noise similar to that of a chenuke twin rotar helicopter.

Leaks between the turbo outlet and engine intake will affect mpg.

Open thermostats with the engine running cold doesn't affect them much but it is still noticeable. Glow plugs kick in from time to time on the old BMW diesels to help keep the engine warm and improve emissions and mpg but I'm not sure if this is the case with yours. My 1.9 tdi is year 99 and doesn't do this.
 
I just bought a bottle of injector cleaner, is that likely to help at all? The other bits you mention above, are they expensive for a mechanic to diagnose?
 
Worn wheel bearings. You could try and check some of it yourself. Your trouble is finding a good garage trained to perform these inspections and hunt down your problem. I have worked at a garage and although I'm good the garage generally couldn't have been annoyed with that sort of thing and another garage near me that I had to use as the cost of the tool outweighed the cost of the job done by somebody else. I found a that they were full of rubbish and they were supposed to be a vag specialist. Lying useless halions.
 
Thank you, I've enquired with the garage about taking it in. Out of interest what's the correct oil for my model? Also where can I find out correct brake pad fitment so I can order those online.
 
Vw 502-00 specification, fully synthetic, 10w40. Double check your handbook.
 
Thank you, do you know how I find out which fitment my front brake pads are as the online store has several options. Can't find it in my service book. Mine is 130 1.9tdi sport 2004.