It's the crankcase ventilation system I'm referring to. It has a one way valve fitted into the engine lower crankcase to allow gas out but not in. This gas is piston blow by gases that will also contain condensation and some oil/fuel that is unburned. It gets sucked up into the engine induction system to be re-burned to make the emissions cleaner. If the valve or pipe blocks or becomes partially obstructed it interferes with the smooth running of the engine and will start to push oil and oil vapour out of the engine oil filler seal and some times the rocker/valve cover gasket due to increased pressure build up inside the crankcase. The 'mayo' you refer to is the culprit. I'm not saying yours is completely blocked if at all, but from your description it could be something to check if your idle problem isn't sorted. Your garage could check this for you very quickly and reset the idle too.

Yesterday, I filled the car (1422cc TDI estate) to the brim (very carefully) and did a pencil and paper fuel consumption check. I don't do the pencil and paper bit very often as I have found my OBC to be pretty accurate. The car has been used for a variety of trips in the last 3 weeks and the one tank of fuel has sufficed nicely. There was still plenty left too, probably just over a quarter of a tank. Due to the holidays etc the car had covered just a lowly 400 miles in those 3 weeks, mostly shorter trips around town and to work with my wife, but a few longer spins of 30-40 miles on dual carriageways, country roads etc. There were several icy morning starts and lots of in traffic work too. The pencil and paper method showed the car had done 52.83mpg for the 400 miles. The OBC showed the car had done 53.4mpg. A difference not worth bothering with and pleasing to know the computer is in fairly good agreement with me. Our 1300 petrol Fiat Punto and a petrol Toyota Yaris with the 1300 engine on the same trips in previous years, albeit in slightly warmer conditions were both in the region of 30-32mpg without the performance of the TDI either and had the higher road tax figure too. I have a nice warm smug feeling at this...tee hee!!

Edited 24 January, 201115 yr by Estate Man

Yesterday, I filled the car (1422cc TDI estate) to the brim (very carefully) and did a pencil and paper fuel consumption check. I don't do the pencil and paper bit very often as I have found my OBC to be pretty accurate. The car has been used for a variety of trips in the last 3 weeks and the one tank of fuel has sufficed nicely. There was still plenty left too, probably just over a quarter of a tank. Due to the holidays etc the car had covered just a lowly 400 miles in those 3 weeks, mostly shorter trips around town and to work with my wife, but a few longer spins of 30-40 miles on dual carriageways, country roads etc. There were several icy morning starts and lots of in traffic work too. The pencil and paper method showed the car had done 52.83mpg for the 400 miles. The OBC showed the car had done 53.4mpg. A difference not worth bothering with and pleasing to know the computer is in fairly good agreement with me. Our 1300 petrol Fiat Punto and a petrol Toyota Yaris with the 1300 engine on the same trips in previous years, albeit in slightly warmer conditions were both in the region of 30-32mpg without the performance of the TDI either and the higher road tax figure too. I have a nice warm smug feeling at this...tee hee!!

OOH top trumps is it. Right, my turn 1.4 TDI DPF Hatchback Greenline :moon:

Mixed driving with motorway/dual carriageway and town sections. Motorway speeds of.......well, mostly outside lane with the odd middle lane to let the rep in the BMW past. Cold weather with scraping off of ice and a few sub zero early mornings and evenings. 62 mpg. This is pencil and paper method. My OBC over reads consistently by about 7 mpg.

Outside temp makes a huge difference. Once the temp goes above about 5 deg C my mpg goes straight back up to near 70 mpg. :strong: Near zero or below it goes to 62 ish as stated

I discovered that in my case its more economic to accelerate quickly in the torque band to the speed desired then just shift straight to cruise. Gently easing up for some obscure reason is less efficient.

My low fuel warning usually comes on around the 600-650 mile mark.

I used to be able to justify my motorbikes to my better half on the basis of economy. Sadly my Greenline is better than my trusty old 500cc bike so I will have to think up a new excuse for getting the Transalp or F650 I am hankering after.

Woo...Hoo!!! lovely fuel consumption Raisbeck. There is no doubt that the Greenline purchase does pay off. I think if I had tried I could have managed another 2-3mpg + without any real difficulty. But to be honest most of the time I don't pay much attention to the OBC. I tend to 'challenge' it if we out for a weekend drive maybe but that's about it these days. On winter diesel I'm pleased, as very obviously you are too.

I know what you mean about the motorcycle. My V-twin Suzuki 1000cc only manages 31mpg around town and pottering about in the country. Not very good. On a run it can manage 48-50mpg which is ok but it still doesn't compete with the 65-74mpg I can get in the car, plus the car tax is cheaper too. Obviously, the bike performance is OTT, it can top 140mph. My GSX1400 can hit a limited speed of 152mph and 0-62mph in just 2.57seconds. But you have to pay for that performance with poorer fuel economy. But I wouldn't swap my bikes for anything.

Woo...Hoo!!! lovely fuel consumption Raisbeck. There is no doubt that the Greenline purchase does pay off. I think if I had tried I could have managed another 2-3mpg + without any real difficulty. But to be honest most of the time I don't pay much attention to the OBC. I tend to 'challenge' it if we out for a weekend drive maybe but that's about it these days. On winter diesel I'm pleased, as very obviously you are too.

I know what you mean about the motorcycle. My V-twin Suzuki 1000cc only manages 31mpg around town and pottering about in the country. Not very good. On a run it can manage 48-50mpg which is ok but it still doesn't compete with the 65-74mpg I can get in the car, plus the car tax is cheaper too. Obviously, the bike performance is OTT, it can top 140mph. My GSX1400 can hit a limited speed of 152mph and 0-62mph in just 2.57seconds. But you have to pay for that performance with poorer fuel economy. But I wouldn't swap my bikes for anything.

Some more comparison economy figures for you - from my 2006 (Mk1) 1.4TDI estate.

From the on-board computer I've had 66-94mpg on my 24 mile commute.

I find this is about 10% optimistic compared to tank-to-tank calcs. These give me an average of 65mpg over 2 years and nearly 30,000 miles.

Outside temperature makes a difference; drop 10 degrees C and I drop 5mpg.

Interesting comments on the revs; I have tried all sorts of driving styles and I find low revs = best economy, I'm frequently in 5th gear by 40mph. Mind you it does sound like a doodlebug driving like that!

Simon

I'm in a bit of a dilemma, car is 1.4 tdi and on a 08 plate so 4 years old this may, it's the timing belt when should I get it done car has only done 50,000 miles I think it's 3 or 4 years or 65,000 should I wait or replace ?