Stickies for fuel consumption

[MilosB]

in a very steep street city (on a hill most of the time) very few roads are level I get 12-15 L/100km = 24 - 18 MPG is this to high ? or i should start finding where does the fuel drip (i have to say the trip is 1km and the car barely gets up to temperature)
on a high way - 120km/h + some local loads at 80km/h all the way on a CC i got 6l/100km = 47MPG on a 800km trip of which 200km is a up and down a hill and AC on as it was cooold
is it any god ? 1.9dci at 154oookm. I suppose the city milage is very low

[AlexB]

47mpg on a motorway with hills looks OK. If the car has DPF, then it even more impressive. Without hills, DPF and on more economical tyres I get 50-55MPG at motorway speeds (70mph). What tyres, tyre pressures and gearbox oil are you using? The gearbox, by the way, consumes a lot of fuel, as its losses are about 15-20%. The aircon is also taking a couple or percent.

in a very steep street city (on a hill most of the time) very few roads are level I get 12-15 L/100km = 24 - 18 MPG is this to high ? or i should start finding where does the fuel drip (i have to say the trip is 1km and the car barely gets up to temperature)
on a high way - 120km/h + some local loads at 80km/h all the way on a CC i got 6l/100km = 47MPG on a 800km trip of which 200km is a up and down a hill and AC on as it was cooold
is it any god ? 1.9dci at 154oookm. I suppose the city milage is very low

[MilosB]

yes, i would say dpf still in place (only had the car once up when being inspected before the purchase) and no map changed on ECU, and no errors etc.
i don't know what oil is in the gearbox (what is recommended) as the car had its fluids changed before my purchase (I made an irefusable offer to a long period family friend, the car wasn't for sale so it wasn't advertised and prepared for sale) tires are all winter, michelin up front 195/95/15 and same on rear but good year, 2.2 on both to give good footprint and equal tire wear (on the highway i know i should increase it, but i forgot )

today, going home from work, long downhill, at 50km/h and in neutral (just for this test, I know it is not safe) and turned the ecu to current fuel consumption and it showed 6 L/100km which is around 50MPG on idle (engine still cold). when it gets worm the millage goes up a bit.

[AlexB]

Hi Milos,

Stock gearbox oil is ELF Tranself TRX or NFP 75w80, GL4+ (almost GL4 and GL5 in the same time), the thinnest for the grade. I use a better one, which significantly improves gearchange and has a much wider temperature range: Motul Gear 300 75w90, which is a motorsport lubricant based on esters providing exceptional boundary lubrication.

The tyres. It is good that the Michelins are on the front, as they are not as grippy as the GoodYears on the back. The pressures seem to be OK-ish, slightly unbalanced in the direction of understeer. I would be using 2.4/2.0 front/rear for safety.

The instantaneous fuel consumption when coasting seems a bit too high, although it can be the effect of the warming-up mode or DPF regeneration. I doubt that the internal friction in the engine is so high that it requires so much fuel to idle. In diesels, what you burn all comes back as power, unless the DPF regeneration mode is on. I hope the fuel is not leaking. Speaking of which, it potentially can be an excessive return flow from the injectors (there is a test for this involving 4 bottles attached to 4 return pipes). Anyway, try the same on warm engine before anything else.

In general, expect to get under 30mpg in the first 10km in winter. Having an oil in SAE 0w grade or a fully synthetic 5w may help.

Yet another thought is that the fuel consumption figures can be very imprecise on a short run. I see nothing disastrous in your story at present.

[MilosB]

thanks a lot
will change the tire pressure, and maybe change the oil around the chrismas, as that will be the only time i will have in day time. also will try out the return test, but the car has the power it should, it seams i should do a fast run on local road and regenerate the DPF as the high way was at 1800rpm to 2ooo and also in the city I'm not to agresive regarding the rpm.

[whitewhale23]

Megane 1.5dci 100 04 plate. Came back from Hillingdon to south Birmingham, reset the trip computer before getting on the M40. Followed a lorry all the way at 55mph. Drove very carefully. trip computer reached 99.9mpg after 75 miles. Would not go any higher! Is this the highest value you can get from the trip computer?
Only had the car a month, Filled up twice and returned 73mpg on the first tank, 70.1mpg on the second. I usually do most of my driving in the countryside with 30% urban driving.

[shakinthatass]

My 2005 1.5dci managed 82.9mpg over a 500+ mile drive with a mixture of mootorways, city and country roads, 3 adults and two kids, boot nearly full and aircon on throughout most of the journey's.

by the way, I have a bluetooth obd2 device and it tells me at idle, the engine consumes 0.8 litres of fuel per hour, with the aircon on, it goes up to 1.0 litre per hour.

I too have had it off the clock past 99.9mpg when I had a habit of resetting the trip computer in amazement at the fuel economy, but you cannot keep it up at 99.9mpg forever - it eventually settles to what the car does on average and a major player in that figure is driver skill with eco driving.

Thats why I bought this car fuel economy is up there with the hybrids and beats some of them!

Off the subject, but does anyone have the service light + check injection message on their dash? I know how to remove this cheaply without the can clip!

[welbeck]

I've gota 1.9dci and get 50+mpg round town and 70+ on a long run, the best being 73.2 from a cold start Mansfield to Greenwich at a steady 70 mph