audi b8 tdi 140, 180k- bad mpg runs well - audi vs indy?

[mikiesb]

Hi

My 2008 b8 2.0 tdi start stops runs well, just bad economy.

Car has covered 180,000 miles and been well maintained by main dealer and then independent.

Now gone for a audi health check, - nothing to report really apart from leaky egr valve - but told not a problem by audi main dealers..

Checked service history and the egr valve and coolant temperature sensor have never been replaced..

Got an independent to check the coolant temperature sensor - VAGcom said it was fine.. they said
EGR valve leaky and likely to perish a hose in the engine bay and best to get it changed etc. ??

Called Audi maindealer back they said this isn't likely to happen.. and that master technician said nothing
wrong with egr apart from a little leaky..

Audi main dealer said coolant temperature sensor is common and relates to poor MPG, also have read up that
the coolant temp sensor isn't likely to show up faulty on the VAGCOM ..

Help !!!

[mikiesb]

bump

[PositronicRay]

How long have you had the car, and how bad is the MPG?

[mickthemechanic]

Am interested to learn how a faulty temperature sensor affects MPG on a diesel.

[anonymous-user]

sticking calipers can be a culprit.

what is bad mpg thou, i have a octavia tdi 130 get mids 40's never much more.

[Condi]

They all do bad MPG imo. For comparison my 2010 b8 180hp tdi has done 41.5mpg over 40,000 miles - although there are a lot of long runs in there. Around town I can easily get 32/35mpg.

[mikiesb]

Hi

Well I've since filled the car right up empty to max on standard supermarket diesel, based on current estimations (half way through the full tank) I am getting 450-470 miles for 57 litres of diesel so I think around 37 mpg, hope my calculations are ok.

I appreciate my car is high miles but I was hoping for a bit more than that, had the car 3.5 years and it's never had the coolant temperature sensor replaced.. which according to audi dealers is a common part to replace.

There's various links on the net re coolant temperature sensor are a common part to replace for bad mpg will try and find the links I found again..

I presume sticking calipers is easy for a mechanic to check out?

Edited by mikiesb on Thursday 1st December 23:57

Edited by mikiesb on Thursday 1st December 23:59

[Blaster72]

The coolant temp sensor is about £20 from Audi and takes minutes to change, the EGR can affect MPG if the valve or hoses are leaking.

I'd suggest changing both and seeing how you get on. Get a genuine Audi temp sensor though as I changed mine with a pattern part and it failed in less than a year. The Audi one lasted until I sold the car.

If you're tight for funds, you can monitor the temp output with VAG COM. They normally stick at a warm temp making the car hard to start from cold (at least on the petrol versions).

Other things - do you have roof bars fitted and are the tyre pressures all correct?

[mikiesb]

Hi

quick updates, 430 miles for £63.00 - 35mpg

Tyres pressures fine, no roof rack, majority of driving is solo.

Calipers not looked at, asked another mechanic.. and he said egr valve and coolant temperature won't affect MPG.. and he's another specialist.

Really appreciate people's inputs but back to square one will drive the car and ignore the mpg..

Thanks again

[SteBrown91]

Cool ant temp will affect mpg as if the car thinks the coolant is still cold then it will pump more fuel in to get it to heat up