Poor MPG

..... · 13th July 2014, 13:39

Ok I'm looking for some ideas as to why my mpg has gone down.

Motorway driving at 70/75 mph the car will only return just over 44 to the gallon.
It used to give more than that.

The car is a diesel manual with the 160 map on it done by Brian.
The engine has had a tetra clean treatment. The oil has just been changed along with the crankcase breather filter.
It's also had new vitron O rings fitted I got from Jules.
It has an ERG bypass fitted and an inline thermostat fitted ( engine temp measured at 87 degrees on the T4 session)
The car has only done 94 k

When I noticed this a few weeks ago I took the car to Rich and he put it on his T4 which confirmed the Maf sensor was fine but said two of the injectors were iffy. I have had both of these injectors refurbished and although the car runs smoother it has made no difference to the mpg.

I've just come up from London and over a 300 mile round trip (nearly all motorway) the car has still only returned 44.1 mpg.

Has anyone got any ideas whats causing the poor mpg?

James.uk · 13th July 2014, 13:47

44 mpg from a car the size of yours is very good.

I know we get a lot of tales about mpg but if you can get over 40 mpg out of the huge cars we drive then you are doing very very well.

How did you determine your mpg? if it was via calculating it via the brim to brim system, then it will be pretty accurate. Any other system will be iffy..

...

..... · 13th July 2014, 13:51

I confirmed the mpg by brim to brim on 2 separate occasions.

I used to get just over 50 mpg doing long trips. I don't drive the car fast or rev it much. In fact I get nearly 40 mpg out of my works van and that weighs 2.8 tons!

Jim W · 13th July 2014, 13:52

Check turbo hose for splits or holes also check O rings have seated properly the bottom one has a tendancy to pinch on fitting also check all air seals are tight

..... · 13th July 2014, 13:59

Quote:

Originally Posted by Jim W

Check turbo hose for splits or holes also check O rings have seated properly the bottom one has a tendancy to pinch on fitting also check all air seals are tight

Turbo hose was replaced last year and mpg was good up to about 6 weeks ago. I fitted the O rings in November so it would be very unlikely that they could be causing a problem now. Also I did it with the bumper off so I know they went in properly.

..... · 13th July 2014, 14:03

Im wondering if it could be something to do with the tetraclean although in theory that should improve the mpg. After I had it done the car wasn't usd for 5 weeks. It was after that that I noticed the drop in MPG.

Doc Evil · 13th July 2014, 15:09

Have you changed the air filter and fuel filter it might be breathing like an athsmatic kitten
Also are your tyre pressures correct and in this hot weather are you drivig with window open
Doc

..... · 13th July 2014, 15:42

you don't open widows.... that lets the outside in.
Check tyre pressures each week.
Air filter is fairly new.

minty2 · 13th July 2014, 17:28

I'd be inclined to carry out a full inspection of the intercooler. Look for holes in the plastic end pieces and the main body matrix. I had poor MPG and low power before discovering a gaping hole! A second hand refurb off a fleabay dealer fixed both.

Quote:

Originally Posted by .....

Turbo hose was replaced last year and mpg was good up to about 6 weeks ago. I fitted the O rings in November so it would be very unlikely that they could be causing a problem now. Also I did it with the bumper off so I know they went in properly.

..... · 13th July 2014, 17:32

Quote:

Originally Posted by minty2

I'd be inclined to carry out a full inspection of the intercooler. Look for holes in the plastic end pieces and the main body matrix. I had poor MPG and low power before discovering a gaping hole! A second hand refurb off a fleabay dealer fixed both.

the car has bags of power...

13th July 2014, 13:39	#1
..... Loves to post Black ROVER 75 Join Date: Nov 2011 Location: Somewhere Posts: 339 Thanks: 5 Thanked 17 Times in 7 Posts	Poor MPG Ok I'm looking for some ideas as to why my mpg has gone down. Motorway driving at 70/75 mph the car will only return just over 44 to the gallon. It used to give more than that. The car is a diesel manual with the 160 map on it done by Brian. The engine has had a tetra clean treatment. The oil has just been changed along with the crankcase breather filter. It's also had new vitron O rings fitted I got from Jules. It has an ERG bypass fitted and an inline thermostat fitted ( engine temp measured at 87 degrees on the T4 session) The car has only done 94 k When I noticed this a few weeks ago I took the car to Rich and he put it on his T4 which confirmed the Maf sensor was fine but said two of the injectors were iffy. I have had both of these injectors refurbished and although the car runs smoother it has made no difference to the mpg. I've just come up from London and over a 300 mile round trip (nearly all motorway) the car has still only returned 44.1 mpg. Has anyone got any ideas whats causing the poor mpg? Last edited by .....; 13th July 2014 at 13:52..

13th July 2014, 13:52	#4
Jim W Gets stuck in Rover 75 Contemporary V6 Join Date: Sep 2013 Location: Neath Posts: 516 Thanks: 93 Thanked 89 Times in 73 Posts	Check turbo hose for splits or holes also check O rings have seated properly the bottom one has a tendancy to pinch on fitting also check all air seals are tight __________________ [SIGPIC][/SIGPIC] Wee V6 Beastie Came off production line 4 days before Longbridge closed No 675 out of 686 made

13th July 2014, 15:09	#7
Doc Evil Gets stuck in Rover 75 1.8 Classic Saloon Join Date: Jan 2014 Location: Newton Abbot Posts: 823 Thanks: 46 Thanked 175 Times in 144 Posts	Have you changed the air filter and fuel filter it might be breathing like an athsmatic kitten Also are your tyre pressures correct and in this hot weather are you drivig with window open Doc __________________ NOT EVIL REALLY BUT REALLY A DOC

13th July 2014, 13:47	#2
James.uk Passed Away 2002 Pale Blue. Rover 75 CDTi Connoisseur auto. 170K miles Join Date: Dec 2008 Location: Near the M67. Posts: 14,509 Thanks: 199 Thanked 585 Times in 397 Posts	44 mpg from a car the size of yours is very good. I know we get a lot of tales about mpg but if you can get over 40 mpg out of the huge cars we drive then you are doing very very well. How did you determine your mpg? if it was via calculating it via the brim to brim system, then it will be pretty accurate. Any other system will be iffy.. ...

13th July 2014, 13:51	#3
..... Loves to post Black ROVER 75 Join Date: Nov 2011 Location: Somewhere Posts: 339 Thanks: 5 Thanked 17 Times in 7 Posts	I confirmed the mpg by brim to brim on 2 separate occasions. I used to get just over 50 mpg doing long trips. I don't drive the car fast or rev it much. In fact I get nearly 40 mpg out of my works van and that weighs 2.8 tons!

13th July 2014, 14:03	#6
..... Loves to post Black ROVER 75 Join Date: Nov 2011 Location: Somewhere Posts: 339 Thanks: 5 Thanked 17 Times in 7 Posts	Im wondering if it could be something to do with the tetraclean although in theory that should improve the mpg. After I had it done the car wasn't usd for 5 weeks. It was after that that I noticed the drop in MPG.

13th July 2014, 15:42	#8
..... Loves to post Black ROVER 75 Join Date: Nov 2011 Location: Somewhere Posts: 339 Thanks: 5 Thanked 17 Times in 7 Posts	you don't open widows.... that lets the outside in. Check tyre pressures each week. Air filter is fairly new.