MPG still disappointing

peelaaa · 24th March 2010, 16:58

When I first bought my cdti tourer (with 23k)it was getting approx 48mpg on average but in the 50's on a steady run. At about 50k the mpg dropped to about 40mpg.
I fitted a new pb maf as well as a synergy 2 and have it set to 6.
The engine seems to be running fine but the mpg is still at the 40mpg level.

The pcv was changed about 20k ago.
Is there anyhting else i should be looking to service?
Air and oil filters are changed at service intervals.

What could it be, as I am seriously thinking of getting another car as the mpg is disappointing.

1gp · 24th March 2010, 17:30

i see you have not changed or checked, the thermostat . this is a very common fault , and will effect mpg alot. do a search on here and you will find pages on the subject....

JohnDotCom · 24th March 2010, 17:33

Check as advised above using the on board diagnostics that the Thermostat temperature, once car is at running temperature (ignore gauge as that get to normal at 77C)
The temperature should be 88C if not the Thermostat needs changing.
Jules can supply at a good price or do the fitting to.
You can easily loose 5MPG with this faulty.

Also check your injectors are running properly and do a leak back test if above doesn't sort.

peelaaa · 25th March 2010, 17:46

Thanks, I will check the engine temperature when I get a bit of time, if it was the thermostat at fault, can running the engine at cooler then recommended cause excess wear to engine?

1gp · 25th March 2010, 21:56

Quote:

Originally Posted by peelaaa

Thanks, I will check the engine temperature when I get a bit of time, if it was the thermostat at fault, can running the engine at cooler then recommended cause excess wear to engine?

no mate , dont worry about that , just get it done , if it needs it, and get your mpg back on track

Snagger · 25th March 2010, 22:25

You may well have a choked EGR Valve, split intercooler hoses, dislodged or worn out intercooler seals, clogged fuel filter.or indeed as stated a partially working thermostat.You will notice your consumption losses the greatest on slow speed short runs if the thermostat is stuck open, or has become lazy, due to the engine not really getting to hot.

Groover.

peelaaa · 7th April 2010, 16:18

Finally checked temperature of coolant. The reading did not go over 82 C, averaged around 80-81 C.
Looks like I need a new thermostat....

1gp · 7th April 2010, 16:55

Quote:

Originally Posted by peelaaa

Finally checked temperature of coolant. The reading did not go over 82 C, averaged around 80-81 C.
Looks like I need a new thermostat....

yep , at that temp yes . like already been said also check intercooler seals , they also could be starting to fail ... check all the common things and you wont go far wrong.

also check your temp at motorway speeds 70 , 80 mph for a good few miles , just to be 100 % .

jcwatrichmond · 8th April 2010, 07:49

Have you checked the wheels for binding brakes or other restrictions? This can have a big effect on fuel consumption.

JCW

GERFIX · 8th April 2010, 08:44

I've just done my first full brim to brim since fitting my new thermostat and my MPG has gotten worse!

I know the stat is now working properly going by the diagnostics. The only other thing I've changed is the air filter to a K&N but surely that wouldn't knock the mpg down? I might give it another couple of brim to brims just to confirm the mpg but I may be reverting to a standard filter as a further trial soon!!

24th March 2010, 16:58	#1
peelaaa Posted a thing or two 75 cdti 2004 contemporary Join Date: Apr 2008 Location: meath Posts: 1,551 Thanks: 272 Thanked 80 Times in 58 Posts	MPG still disappointing When I first bought my cdti tourer (with 23k)it was getting approx 48mpg on average but in the 50's on a steady run. At about 50k the mpg dropped to about 40mpg. I fitted a new pb maf as well as a synergy 2 and have it set to 6. The engine seems to be running fine but the mpg is still at the 40mpg level. The pcv was changed about 20k ago. Is there anyhting else i should be looking to service? Air and oil filters are changed at service intervals. What could it be, as I am seriously thinking of getting another car as the mpg is disappointing.

8th April 2010, 08:44	#10
GERFIX I really should get out more....... MINI COOPER S Join Date: Nov 2007 Location: Tranent, East Lothian, SCOTLAND Posts: 2,834 Thanks: 0 Thanked 0 Times in 0 Posts	I've just done my first full brim to brim since fitting my new thermostat and my MPG has gotten worse! I know the stat is now working properly going by the diagnostics. The only other thing I've changed is the air filter to a K&N but surely that wouldn't knock the mpg down? I might give it another couple of brim to brims just to confirm the mpg but I may be reverting to a standard filter as a further trial soon!! __________________ .......................................Colin http://i245.photobucket.com/albums/g...Cooper-S-2.jpg

24th March 2010, 17:30	#2
1gp I really should get out more....... mgzt, 135 cdti , manual , in solar red.also own a mgtf. Join Date: Jan 2010 Location: notts. Posts: 2,105 Thanks: 28 Thanked 40 Times in 39 Posts	i see you have not changed or checked, the thermostat . this is a very common fault , and will effect mpg alot. do a search on here and you will find pages on the subject....

24th March 2010, 17:33	#3
JohnDotCom * Rover 75 FaceLift Tourer CDTi 170BHP Auto ConnSE 2005 Model Starlight Silver Join Date: Nov 2006 Location: Abergele Posts: 28,735 Thanks: 0 Thanked 6 Times in 5 Posts	Check as advised above using the on board diagnostics that the Thermostat temperature, once car is at running temperature (ignore gauge as that get to normal at 77C) The temperature should be 88C if not the Thermostat needs changing. Jules can supply at a good price or do the fitting to. You can easily loose 5MPG with this faulty. Also check your injectors are running properly and do a leak back test if above doesn't sort.

25th March 2010, 17:46	#4
peelaaa Posted a thing or two 75 cdti 2004 contemporary Join Date: Apr 2008 Location: meath Posts: 1,551 Thanks: 272 Thanked 80 Times in 58 Posts	Thanks, I will check the engine temperature when I get a bit of time, if it was the thermostat at fault, can running the engine at cooler then recommended cause excess wear to engine?

25th March 2010, 22:25	#6
Snagger Gets stuck in ROVER 75 CDT CLUB SE 02 Join Date: Aug 2009 Location: Kent Posts: 658 Thanks: 30 Thanked 141 Times in 87 Posts	You may well have a choked EGR Valve, split intercooler hoses, dislodged or worn out intercooler seals, clogged fuel filter.or indeed as stated a partially working thermostat.You will notice your consumption losses the greatest on slow speed short runs if the thermostat is stuck open, or has become lazy, due to the engine not really getting to hot. Groover.

7th April 2010, 16:18	#7
peelaaa Posted a thing or two 75 cdti 2004 contemporary Join Date: Apr 2008 Location: meath Posts: 1,551 Thanks: 272 Thanked 80 Times in 58 Posts	Finally checked temperature of coolant. The reading did not go over 82 C, averaged around 80-81 C. Looks like I need a new thermostat....

8th April 2010, 07:49	#9
jcwatrichmond Loves to post Rover 75 1.8T 2003 Club SE Join Date: Jan 2009 Location: Solihull, Posts: 370 Thanks: 0 Thanked 0 Times in 0 Posts	Have you checked the wheels for binding brakes or other restrictions? This can have a big effect on fuel consumption. JCW