C5 mpg

davo77 · Unread post by **davo77** » 28 Jan 2010, 09:05

Hello everyone, I have a 04 2.0hdi Lx with 53k which has the trip computer upgrade and cruise control retrofitted. Here goes having reset trip on a recent drive I had covered 343.4 miles and used 26.96 litres having brimmed tank. mpg calculator .Co.Uk says I achieved 57.9mpg, but computer said 48mpg this was mainly done on motorway at 65mph. Are these always innacurate and what do other people achieve, thanks look forward to hearing from you.

Unread post by **citroenxm** » 28 Jan 2010, 10:06

48mpg or 57mpg, id be WELL pleased with either, considering the size of the C5 and shes only eith a 110 or 90bhp... my guess is with those figures shes a 110bhp...

Trip computers always either over read or seriously under read, but are only a rough guide and never accurate!

Paul

davo77 · Unread post by **davo77** » 28 Jan 2010, 10:20

Hi yes it is a 110, well pleased with her,only problem I have had has been rear caliper corrosion. Been in family since 11k.

Unread post by **Old-Guy** » 28 Jan 2010, 10:37

Mileage derived via the 'speedometer' (i.e. drive train) must always be inaccurate because the rolling radii of tyres varies according to tyre design, wear, pressure and speed.

The fuel meter is trying to measure accurately the small amounts of fuel actually injected and which vary enormously.

IMHO the only way to do accurate fuel consumption checks is to determine the error of your odometer over several hundred miles of your typical driving from sat nav figures. Then you can correct the milage for brim-to-brim consumption.

I know of a case of an idiot in a Transit who ran out of fuel because the trip computer told him he still had 6 miles worth of diesel in the tank and he was only 3 miles from base!

jonathan_dyane · Unread post by **jonathan_dyane** » 28 Jan 2010, 16:32

davo77 wrote:Hello everyone, I have a 04 2.0hdi Lx with 53k which has the trip computer upgrade and cruise control retrofitted. Here goes having reset trip on a recent drive I had covered 343.4 miles and used 26.96 litres having brimmed tank. mpg calculator .Co.Uk says I achieved 57.9mpg, but computer said 48mpg this was mainly done on motorway at 65mph. Are these always innacurate and what do other people achieve, thanks look forward to hearing from you.

To work out properly:

Convert litres to gallons by multiplying litres by .22
29.96 x .22 = 6.5912

Divide miles travelled by gallons used
343.4 / 6.5912 = 52.1 mpg.

Difference between my result and car computer are likely to be due to inaccuracy of your odometer and/or the tank not being *quite* brimmed.

davo77 · Unread post by **davo77** » 28 Jan 2010, 16:41

Thanks for the reply,thought it was too good to be true,still pleased with 52mpg .

Citroenmad · Unread post by **Citroenmad** » 28 Jan 2010, 19:19

In my expereince 110 HDis always under read. Usually mine says 37MPG which is usually 42ish when i work it out at the pumps. Which is what i get on a weekly basis, though my commute is 60 miles motorway and then over an hour in very slow crawling traffic - huge fun! Though on monday it took me 2 hours to crawl into Newcaslte

which really had a big effect, im now getting about 32 to the gallon

Ive never had over 50MPG from any 110HDi, we've had three now, best ive had was 47MPG actual, about 43 on the trip computer if i remember rightly. Though i never sit at below 70 on motorways.

However our facelift C5 over reads by around the same amount, 4-5MPG.

They are good to use as a guide, but are rarely accurate.

davo77 · Unread post by **davo77** » 28 Jan 2010, 21:08

Thanks for the insight,have been using shell optimax for a few months now seems to make it run smoother, could be why its getting good figures.

Joe Pineapples · Unread post by **Joe Pineapples** » 29 Jan 2010, 16:07

My C5 runs around 46mpg, week in week out, on my daily 80 mile commute to work, according to the trip computer.
Strangely, removing my roof rack and bike carrier makes absolutely no difference.

davo77 · Unread post by **davo77** » 29 Jan 2010, 18:06

I think these citroens computers all must read below a friend has a C4 1.6hdi and his is always about 10mpg less than what he actually gets.

Joe Pineapples · Unread post by **Joe Pineapples** » 29 Jan 2010, 18:15

They're not really supposed to be uber-accurate I guess. More of a guide than a gauge.

KevMayer · Unread post by **KevMayer** » 30 Jan 2010, 21:48

Just read this thread and realised that there is a minor inacuracy.

The figure should be 57.9 mpg because the original figures said 26.96 litres were used and not 29.96 ltrs which is used to get 52.1 mpg.

davo77 · Unread post by **davo77** » 30 Jan 2010, 21:58

Thanks for that info thought it was,couldn't see mpgcalculator.Co.uk being wrong,had deffo brimmed tank to filler neck both times!

seisporting · Unread post by **seisporting** » 01 Feb 2010, 11:31

Mine only does 29-30 on trip computer.
Using the mpg website to calculate its more near 37 so seems it is inaccurate.

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