TDCi lacking fuel economy?

Mondaveo · 24-10-2017, 11:14 PM

So just something I've noticed/been wondering for some time...

Having owned the Mondeo for two years now I've gotten a sense for the fuel consumption of my individual specimen and it seems to hinge around an indicated 6.5 to 7 L per 100km for my regular driving (predominantly weekend trips to the shops and easy cruising traversing Canberra's main roads). Now, I typically drive in a very relaxed (even pussy-footed) fashion, yet this is well above the official claimed combined cycle fuel economy figure of 6.2L/100km, and reading these forums I've seen members post fuel economy figures that I can't hope to touch even in highway driving (e.g. cobrin's 5.8L/100km even with giving it a bit of a bootfull - but admittedly following an overhaul).

I wasn't sure how much I could trust the dashboard-indicated average figure so I went back and did the maths for the last three times I filled the tank. (I always buy fuel at Costco Majura and tend to only fill the tank when we're going away, for day-to-day driving I'll only partially fill the tank to $50 or so. I also only fill to the first click-off of the pump.) So going off the distance travelled and how much it took to refill the tank, these are the figures I got:

63.74L fill after 979.0km (includes 500km highway to/from Sydney)
= 6.51L/100km
173.82L (three partial tanks plus a complete fill) after 2541.6km (500km highway to/from Sydney, the rest around ACT)
= 6.84L/100km
62.60L fill for 992.0km (includes 700km highway to/from/around Bathurst)
= 6.31L/100km

Considering the amount of highway running I'm disappointed not to be getting better economy (though admittedly the car does tend to be loaded up for those big trips)... so, could there be something wrong or is it all in my head? What do the rest of you get for mileage and how are you computing it?

whitelion65 · 25-10-2017, 09:27 AM

We are similar. Sits around 7.2 during the week. Would drop into high 6's on a decent run.
I think the wagon shape (aero), and extra weight contributes too.
I console myself by comparing it with the V8 wagon!

NZ XR6 · 25-10-2017, 12:30 PM

I assume both cars are MC models?

My MB regularly manages about 5.5 l/100 km on trips. When it was newer, it would never go below 6, but a set of green tyres (Michelin Primacy 3) and Fuchs oil both resulted in small but definite improvements.

That's on typical NZ roads cruising at 110 km/h when possible. Just me plus a boot and back seat full of tools, etc. for work.

cobrin · 25-10-2017, 12:38 PM

TBH it looks completely normal Mondaveo, my average around Cairns was 6.8 to 7.2 and during summer months the worst around 7.5-7.8 because the AC is always on, that's typically flat driving around here, it's always been within that range (calculated at the pump). It's only when I take everyone out to a Gorge / Waterfalls / Hot Springs / Tourist attraction that I get to stretch it's legs and sometimes go up the Range (Tablelands). And there's plenty to see, already knocked off 8-10 attraction sites with over a doz to go in my immediate surrounding areas

That last 5.8 Cairns to Cardwell has been blown out to 6.4 and possibly higher because of the missus work run is included on the same tank. Unfortunately the missus put ~$20 in since. That fill up on the last trip was on the way out of Cairns so after filling up it's on the HWY for the best possible situation to get those figures. I mean that average speed tells the story 82kph, typically that's 33-37kph during the daily grind. 3 coles cooler bags with food/drink, a 5L drinking esky, change of clothes for all and 3 scooters was all I had in the boot so it was pretty light on.

Michelin PS3 Tyres on front 38psi (almost due), PS4 on rear 40psi (fresh). CControl used all the time till someone is holding me back. +10kph over and overtaking well it's not uncommon to see a buck fourty or *cough* bit higher in places. Previous PB Cairns to Airlie Beach 6.1 on a stinking hot summer day 48DegC on the HWY right when the fan speed controller failed just out of Cairns so no AC all the way down...made damn sure there was on the way back.

Post belt change has made a difference and it's feeling good and I'm really happy moving forward but one thing I've noticed (anecdotally) is the characteristic/personality between the engine in relation to speed and the torque converter. I feel it doesn't pull hard like it use to from low to mid range. I feel the PCM is allowing the TC to slip for torque limiting functions early on in the lower gears letting the engine rpm to increase which is suppose to, to keep the output high/er and protect the trans for those gears, so it just doesn't feel like it pulls as hard as it did (and it did from down low) or if it is it feels like a much softer delivery of it. No other changes anywhere else can be found. Other than a remarkable reducing of soot and the engine being quieter so now the AC compressor seems louder lol. (no doubt placebo)

So yours seems pretty spot on with an extra ~50kg over the hatch, then whatever you have in the boot and where you drive. I mean we're talking points of a litre here.

manchu · 25-10-2017, 05:43 PM

I've never really been happy with my MC TDCi wagon economy but it's been a bit hard to gauge.

I currently have a roof basket fitted which kills economy and puts me up to mid 8's for my daily drive. Not much better on long trips. IIRC the best I've got is about 6.5.

The other thing I reckon comes into play is the DPF regen. I was monitoring mine for a few weeks and saw regens every 200km or so.

bundybear75 · 25-10-2017, 07:54 PM

Sounds fairly normal to me Mondaveo.

My long term average (50,000km) is 6.468l/100km. That is generally cruise set at 115km/h on my regular commute Goulburn to Queanbeyan (now Fairbairn). It has increased a little since I moved out of town to a lifestlye block which has a steep gravel driveway which is a slow 1st gear crawl up and down.

I find if my wife drives the car the fuel consumption increases to around 8l/100km. I've had it as low as 5.7l/100km.

On a side note, the one and only time I filled up at Costco Majura in the Mondeo I put 72 litres in and the fuel gauge was still indicating an 1/8 tank to empty and 100km DTE.

Mondaveo · 25-10-2017, 09:50 PM

Thanks all for the input. I hadn't considered the weight and drag penalty for the wagon body style, but I guess that would be a factor. It seems that each of us with wagons are in fact getting bang-on the same mileage, so I think I can put that one to rest in my mind.

bundybear75 · 26-10-2017, 02:49 PM

Quote:

Originally Posted by manchu

I've never really been happy with my MC TDCi wagon economy but it's been a bit hard to gauge.

I currently have a roof basket fitted which kills economy and puts me up to mid 8's for my daily drive. Not much better on long trips. IIRC the best I've got is about 6.5.

The other thing I reckon comes into play is the DPF regen. I was monitoring mine for a few weeks and saw regens every 200km or so.

How do you monitor the regens? I have never actually noticed mine do one (but it does do 120 km each way trips every day)

My Landcruiser has a basic display on the dash and counts up DPF 1, DPF 2, DPF 3 then resets to DPF 0 - It would do this every 80km or so. It does have an issue with the injectors though.

manchu · 26-10-2017, 10:44 PM

Quote:

Originally Posted by bundybear75

How do you monitor the regens? I have never actually noticed mine do one (but it does do 120 km each way trips every day)

My Landcruiser has a basic display on the dash and counts up DPF 1, DPF 2, DPF 3 then resets to DPF 0 - It would do this every 80km or so. It does have an issue with the injectors though.

OBDII scanner connected to phone. I had a regen fault come up one day so I started monitoring various parameters when driving. DPF soot load, exhaust temp etc etc. when exhaust goes to 600degC it's doing a regen.