High Diesel Consumption On My 2.0 Hdi C5

[Guest Bry]

Can any one help me as I Have a diesel 2.0 HDI C5 and I am only getting average 42 MPG this is driving on a Motaway at about 65 MPH around town its only about 30 MPG. The engine runs OK and drives fine I can not understand why.

I have just done a trip from Southampton via Belgium Paris to home 919 miles and avmpg was 30.5 with four adults plus fully loaded top box and boot and very windy, on the way to UK no top box and just two people avmpg was 41 /C5 02 mdl exc se 5 speed not so bad for a big car. My Scinic on ave gets 55mpg but is only 80bh

[shallishanti?]

I commute 50 miles each day on the A1, with a bit of urban work at either end. My average is now 42 mpg up from 39 mpg. All due to deliberately driving very gently on the accelerator, and not going over 75mph. I did manage a 46 mpg tankfull once.

[Guest Dervman]

Hmmmm; any ideas to look at for lower mpg? I've got a 54 plate 110 VTR HDI (pre-facelift) 2.0. I know the combined is listed as 47mpg, so I was expecting to get around 42-45 mpg. I'm getting 38! Putting the climate into eco mode, it increases to 39 - I got 41 coming down the motorway.

 

40 mile round trip every day, fairly flowing traffic, cross-country and I'm just taking it easy (change gear typically 2 - 2.5k revs).

 

I've only had the car a couple of weeks - bought it as a my previous petrol car was big and giving me 30mpg with a back wind! So with the £120 tax, and prospect of only using £5/day in fuel I went for this 1-owner C5 (57k on the clock). I am basing these figures on what the trip computer is telling me, and then (I'm scared), looking on this forum everyone talks about how it over-reads. If that's the case I'm going to really regret getting this car. I like the C5; not my 1st Citroen and probably not my last! previous was a ZX Volcane TD 13 yrs ago and I still miss it! That I could get into the mid 50's with careful driving...

 

I'm going to pop the air-filter at the w/end and check it's condition. As I remember that derv's are quite prone to dirty filters.

[Guest Visa10E]

I commute from Bradford to Wakefield every day in my 02 2.2 HDi Exclusive on the M606, M62 & M1 with a bit of urban driving at either end, especially the Bradford end and if I drive without a care in the world I'll get 39mpg and around 520-540 miles to a tank (brim to brim calculation), the computer usually being between 1 & 4 mpg out. The other week I did a test and drove entirely with economy in mind and the results were startling I got 665 miles out of the tank with the computer saying 47mpg with the actual mpg at 45, which aint bad, bearing in mind that this involves 25 minutes of stop start traffic out of a 50 min journey. More recently drove to Limoges in France and the data is as follows:

 

Bradford-Dover 290 miles not exceeding 80mph 46.3 on computer 44.54mpg actual

Dunkerque-Limoges 497.5 miles half the journey careful, last 2 hours with the foot down at some points hitting 125mph 42.2 on computer 39.89mpg actual.

 

Point being if you drive like a saint (which I do most of the time due to cost) then you can coax mid 40's mpg out of these big cars, the car I had befor this a 150bhp BMW 320d returned 41-43mpg so the C5's not too bad in my book, but I would have thought that the 110bhp owners out there would be able to better this

[Randombloke]

Other points not mentioned here would include Ronin's tip for checking tyre pressures, and using different pressures to stock.

 

Advice from Ronin re tyre pressures and results

[Guest Dervman]

Interesting what you say Visa10e. Before I started working for myself I used to get the keys to pool cars - Had a 54 plate 318d for the weekend (2.0 - 115 bhp) - and that returned 47mpg ave. Car I just sold was a V70 with a thirsty Turbo to feed as well.

 

I filled up properly last night (rather than £20 here and there), so brimmed, it showed 620miles on the trip. After 70 miles today, the computer is still showing 577 to go, but only 39.2mpg. So the two numbers do not correlate!?

 

68 litre tank = 14.96 gallons.

 

577+70 = 647 therefore 647/14.96 = 43.2 mpg - isn't that what the computer should be reading?

 

Best thing will be, run it down, see what I truly get from the tank - refill and see what that equates to on MPG.

 

My problem is how long I can last in "Driving Miss Daisy" mode... :unsure:

[Guest Dervman]

68 litre tank = 14.96 gallons.

 

577+70 = 647 therefore 647/14.96 = 43.2 mpg - isn't that what the computer should be reading?

 

Ok - I gave in! Computer was bleeping with low fuel warning. Trip said I had 40 miles left. Had driven 560 miles. So filled up... 59 litres exactly (well 59.01) and I used the same pump as last time.

 

Trip was saying average of 37.2mpg. But - 59x 0.22 = 12.98 gallons, and 560/12.98 = 43.1mpg

 

So the computer is reading -5.9mpg or 14% out.

 

This is driving through town (3 miles), 15 miles of x-country and 4 miles of of city driving in rush hour.

[paul.h]

Dervman,

it is worth resetting the trip computer now and again (if not already done), just hold in the button on the end of the stalk. Then say if done on one journey you should find what fuel use you get for that type of journey. If you have had a trip of heavy fuel use such as towing a caravan, it takes many miles before the average mpg gets up to a more normal value unless it is reset.

[Guest Dervman]

Dervman,

it is worth resetting the trip computer now and again (if not already done), just hold in the button on the end of the stalk. Then say if done on one journey you should find what fuel use you get for that type of journey. If you have had a trip of heavy fuel use such as towing a caravan, it takes many miles before the average mpg gets up to a more normal value unless it is reset.

 

Only thing is I like to see what mileage I get from the tank, so I reset the mileage side when I filled. Of course, this then resets the mpg, ave speed and ave mpg as well ;)

 

Only has one trip on the dash, so can't use that either. I reset it everyday to record my mileage (self-employed, so I need to record my mileage). So, I'll just go with my manual recording, and get an idea of the fuel used.

 

I am short-shifting through the gears tho - Town, typically 2k revs, and open road, 2.5k - overtake not much point above 3k, as it runs out of steam. Even at these changes, I'm often pulling quicker than others on the road so thats ok!

 

Got a 200 mile run coming up, so will be looking forward to seeing what the MPG is after that (all motorway)

[paul.h]

'I am short-shifting through the gears tho - Town, typically 2k revs, and open road, 2.5k - overtake not much point above 3k, as it runs out of steam. Even at these changes, I'm often pulling quicker than others on the road so thats ok!'

 

Ah, this seems to be your problem, you are enjoying your driving. Try changing up at 1.5 to 2k revs then may get a few more mpg. The diesel engine torque peaks about 1800rpm so should pull quite happily at this. Our 2.2 hdi runs ok 1.1 to 1.5k rpm for round town use.

[myglaren]

I get around 32mpg around town (very short trips and long periods between them, so the engine never really warms up).

 

Long distances are much better, I did a 633 mile round trip on one tank (65L). There were some very slow (5mph) bits for several miles on the M1 that probably didnt do it any good, also some running around in Bedford/Milton Keynes but had it been all motorway it would have looked better.

 

Speeds were >70 where appropriate and up to the cars top speed at times. It does get booted around a lot that probably drags the economy down a bit.

[Guest Terry Toye]

Not so on my C5. Mine has same engine as yours but with six speed box. I quickly realized that my calculations agreed almost exactly with the computer.

Trip meter Fuel Consumption displayed, wrt real fuel consumption.

Hi John,

Perhaps I should add that I reckon that the Engine Management Computer has a fixed constant in the Software which the Citroen Design team felt would satisfy most Cars, with respect to computing the fuelling of the injectors, (and hence overall fuel consumption displayed).

If you are lucky enough to be in the design 'norm' then you will have fairly accurate readings.

Speaking as an Engineer, cheap test equipment has the calibration set at the factory with a standard setting for the product. More expensive equipment will have the facility to adjust the calibration accurately for each unit built.

Our cars fall in to the former bracket. (Unfortunately)

Of course it is in Citroen's interest to err on the side of an optimistic reading - like mine !!

Terry Toye

[Guest Terry Toye]

Not so on my C5. Mine has same engine as yours but with six speed box. I quickly realized that my calculations agreed almost exactly with the computer.

Trip meter Fuel Consumption displayed, wrt real fuel consumption.

Hi John,

Perhaps I should add that I reckon that the Engine Management Computer has a fixed constant in the Software which the Citroen Design team felt would satisfy most Cars, with respect to computing the fuelling of the injectors, (and hence overall fuel consumption displayed).

If you are lucky enough to be in the design 'norm' then you will have fairly accurate readings.

Speaking as an Engineer, cheap test equipment has the calibration set at the factory with a standard setting for the product. More expensive equipment will have the facility to adjust the calibration accurately for each unit built.

Our cars fall in to the former bracket. (Unfortunately)

Of course it is in Citroen's interest to err on the side of an optimistic reading - like mine !!

Terry Toye

[Guest Dervman]

Ah, this seems to be your problem, you are enjoying your driving. Try changing up at 1.5 to 2k revs then may get a few more mpg. The diesel engine torque peaks about 1800rpm so should pull quite happily at this. Our 2.2 hdi runs ok 1.1 to 1.5k rpm for round town use.

 

Enjoying my driving??? - That's me in "Driving Miss Daisy" Mode!!!

 

1.5-2k maybe too sluggish for the car. I've noticed upto 1.5k, it's a bit laborious, and a couple of times it's flatted on me (feels like the handbrakes on - 2.5k suddenly takes off like a rocket). Friend suggested this maybe a sticking EGR valve!? So going to search forums for this, as noticed a number of people referring to this.

 

Also, when cold 1st thing, I get a high-pitched whistle (not like the normal turbo whistle, much louder, different pitch), which is gone once @ normal temp.

 

Got a WarrantyDirect ('covers everything' warranty), so not to worried about it at the moment - on that note - it was only £20/year more than my old V70 T5 - queried it, and the bloke told me they were as bullet proof as a Volvo, unless a gremlin hits the electrics! Quick search on Autotrader brought up a few C5's with 300k+ miles on the clock!! :o Anyway, sorry I diverse.

 

Back to the MPG - trip says 37, reality is 43. Computer tells me I'm empty, gauge says I'm empty - I only get 59-61 litres in the tank - which suggests I have another 100miles in the tank.