Poor mpg (non-Volvo)

[Kev0607]

Hello all,

I'm just wondering if anyone may be able to point me in the right direction as to whether this is normal or not. If not, what could it be? This isn't based on a Volvo, but hear me out please...

My Dad has a 2017 Citroen Relay van (short wheel base, 2.2 litre euro 6 engine (Turbo Diesel). He bought it brand new in 2017 & its always been serviced on time, if not beforehand. The oil, oil filter & air filter was changed recently (minor service). Last year it had a full service, so the full works including the fuel filter & then prior to that Citroen did the work. Its always had top quality oil & filters used. Tyre pressures are checked regularly & only Texaco fuel is used.

The problem is, the mpg isn't good. As the vehicle wasn't used on motorways up until recently, we never really noticed anything. However, now its travelling longer distances, the fuel costs are adding up. I understand that colder weather has an affect on diesel engines, but the mpg has never been particularly great even when the weather is warm!

I've noticed that the temperature needle doesn't quite sit bang on half way. Citroen looked into it & just said there were no fault codes & "everything appeared normal". It doesn't overheat & isn't using coolant excessively, but does need a top up every now & again.

On a motorway run, it does 33.3mpg according to the tip computer doing 70mph... Supposedly, it should be doing 48mpg extra urban (according to specs). Now I understand that some of these specs mpg figures claimed by the manufacturer's are often optimistic, but even being realistic by knocking a few mpg off the claimed mpg & accounting for inclines, what's being achieved is still way off the mark. For example, it does more mpg around town than it does on the motorway? Surely, this can't be normal... I would have thought it would be the opposite (more mpg on motorway than around town) .

Servicing made no difference to the mpg figures. Its using a full tank of fuel a week, which costs around £100 travelling from Manchester to Chester (53 miles each way) for essential work. Its not carrying any weight in the back at all or towing - just the weight of three people (driver & two passengers), fuel & the van itself.

Any ideas? Any help/suggestions is appreciated.

Thanks,

Kev.

[The Thong]

Sounds about right to me for the class of vehicle. Having run and driven vans from various manufacturers, 33mpg isn’t out of the way. I’ve run Ford, Citroen, LDV, Iveco, Bedford etc. I had a Convoy with a Duratorq in it and I’d get 33mpg on a run at 60mph. Ignore the fictitious numbers the manufacturer quote or the trip meter, they’re never accurate.

TT

[DSK]

The first clue is temperature. If its not where it should be, then perhaps the thermostat isn't at 100% efficiency which, will to some degree will impact fuel efficiency. With you also needing to top up, you may have a pin hole in your radiator. Look for dried white residue on all coolant lines and radiator as well as any going to the turbo.

Wheel Alignment - often overlooked but most vehicles tend to be way out of alignment. This will impact fuel consumption.

Even though you have done you part to get it serviced, do not for a moment trust the dealer etc to have done a good job! deliberately missed items despite leading you to believe they are good/renewed is common place. I'd check the condition of the air filter(s) for a start.

Also consider doing a smoke test to see if you have any minor leaks around things like seals or pipework that can't be seen with the naked eye.

[DaveNP]

I'd hazard a guess that the 70mph bit is what is hitting your mpg, whatever they may claim for aerodynamics a van is not a sleek vehicle and going over about 50 mph will increase the fuel consumption exponentially, so 50 to 55 is a 10% increase in speed but a 21% increase in drag and corresponding fuel consumption, 50 to 70 is 40% faster but nearly twice the drag and fuel consumption, Ouch!
If you want to try for better mpg try cruising at 50 on the motorway (warning it will feel like it will take forever to get anywhere )

The 'Extra Urban fuel consumption test is also not done at high speed over a long distance, it's only a few minutes long from standing start to stopped and only about 30 seconds of that are over 60mph, the graph below shows the test cycle, the speeds are in kph 100kph=60mph and the times at the bottom are in seconds, the whole combined test is 1200 seconds or 20 minutes, how they derive meaningful values from such a short test beats me.



Wikipedia on Fuel Consumption tests

[Zebster]

Worth checking for an oddly warm wheel hub after a run to rule out a binding brake.

I've no idea if it's the same for Citroens, but the temperature gauge on my last car (a 2005 Honda Accord diesel) always sat just below half way on a run. This was normal; there was even a thread about it on a Honda forum!

[jason11]

Your mpg sounds about right doing 70 mph in cold conditions. It will probably improve by about 2-3 mpg in warmer conditions but by cruising at 60 you will get 2-3 mpg improvement straight away and in the real world not much difference in your journey time. The temperature gauge is always just under half on these vehicles and perfectly normal. I’ve driven over 750000 miles in the last ten years as a courier driving the Peugeot/ Citroen/ fiat variants and would only be a little concerned if the mpg dropped below 30 overall. Hope that helps.

[Kev0607]

Thanks for the replies all. I've suggested reducing speed to say 60mph to see if that makes a difference. I'm not actually driving this particular vehicle, but the driver has been made aware.

The brakes aren't old, as they were replaced not so long ago. There's still plenty of meat left on them & they aren't binding. Tyres have decent tread & the pressures are also correct.

As for the air filter, that's literally just been replaced. It was a DIY service this time around (not Citroen), so it has definitely been changed. The oil & oil filter were also replaced.

I suppose its a van after all, so the higher roof will be just catching the wind & creating excessive drag. The Transit (2008, mark 7) we have has a lower roof, but that catches the wind too on the motorway. Its slightly better on fuel than the Citroen, but its a much smaller van in terms of dimensions.

[Laird Scooby]

Having had the older ones (1998 ish but this was 20 years ago) as company vans, i'd say 33mpg would have been my bosses dreams come true, it would have halved his fuel bills!

Also something i did find with several Citroen vans (Berlingo and Relay, another boss reported similar with a Dispatch) that when they're new, they're not bad on fuel. After a few thousand miles, that drops dramatically to about half what it did when new.

No idea if the newer ones are the same but wouldn't be surprised if they are.