[DiogoASC]

Hello,

I own an i30 CRDI 128 from 12/2013, the car has made 42.000 Km and since the first day I get bad average L/100Km / MPG, and even on motorways the best I figure I've registered was around 6.5 L/100Km / 45 MPG at 120 Km/h constant speed (premium fuel, 20ºC air temperature, right tyre pressure, unloaded car).... From the 42.000 Km about 35.000 were made in motorways (around 120km frequent journeys), so not to expect injector clog or DPF not regenerating right?
I've complained at the Hyundai shop and all the electronic testing is without problems and they tell me I'm getting normal fuel consumption... Complained at the Hyundai client support and did't get any answer...
Does anyone know a possible cause and solution for this problem? Mechanical fault that doesn't show up on electronic diagnosis?

Thanks for the help!

[Asterix]

Hi DiogoASC

 

What speed do you keep on the motorway..?  Have you tried to do a 50km trip on country roads @ 80-90 km/h and see the consumption for such a trip..?
Are there Mountains where you drive or is it flat land..?

Oh, and one more question: Have your car manual or auto gearbox..?

[DiogoASC]

Hi!

1. My usual speed around 120-130 Km/h (75-80 MPH).

2. Even on country roads, the best figure was around 6,3 L/100Km (45 MPG)

3. No hills, low altitude...

4. Manual gear box.

Thanks

[EmpiriuS88]

I was driving to work 130km/h and 110 kmh back. It showed 5.1 l/100km
Now I drive 150km/h to work and 110km/h from work. Still shows 5L/100km

I drive daily for about 70 km in one way. Just got over 25.000km mark on my i30 GD.

Fuel consumption should be around 5L/100Km for all diesel engines. Just drive it fluidly, not like a mad man.

But that is what the odometer says.

[DiogoASC]

Some times it seem that independently the speed (120-150 Km/h), I see no significant average consumption change...

[eye30]

Does your car have the average consumption bar icon.

If so, display that and see where the white bar tends to lie while driving as this will give you visual comsumption.

[DiogoASC]

Yes it does, but I feel it is a little bit inaccurate...

Today I did an experiment:
After fueling in, I reset the average and then entered the motorway. For 30 km at 120km/h the average was 7L/1000km!!! Then I noticed it started to go down a little and afterwards restarted the average again, the next 70km it went down to 5.4L/100km!!
I now suspect the car may be regenerating the DPF to often. Is it possible? I will try to confirm this.

[AlanHo]

Your odometer is likely to be inaccurate - as is the fuel consumption display.

The only way of checking your actual fuel economy is to first check how accurate your odometer is - I do this by comparing my car's odometer with the distance markers on the motorway over a long distance. My last three cars have all been reading between 2.2% and 2.8%  under. That means that when the car tells you it has travelled 100 km - it has in fact done a greater distance.

Now you need to brim the tank - and brim it until the fuel is stationary in the filler pipe and about to spill over. Make a note of your odometer reading.

Now drive the car until the fuel warning light comes on and refuel it. Again brim the tank until it is on the point of spilling over. Make a note of the odometer reading and the quantity of fuel added.

You can now calculate the actual economy using the distance covered on that tank of fuel and the amount of fuel used. For a totally accurate figure adjust the distance travelled by the result of your odometer accuracy test.

Regarding your concern about the DPF. My experience with two I30's is that they both regenerated at intervals between 350 and 450 kilometres regardless whether motorway travel was involved. It is a myth to assume that speeding on a motorway will keep the DPF clean - it won't - because the DPF does not get hot enough and the more fuel you are using the more particulates are produced.  The Hyundai DPF has to be heated to more than 600 C to burn off the particulates which it does by injecting extra fuel part way down the firing stroke in each cylinder for about 20 miles. The extra fuel burns in the DPF to heat it.

[Hornet]

For information I mention that I just completed a trip Bundaberg to Townsville and return about 2200k. The consumption was 5.32l per 100k. This was in a i30 CRDI, CW, Auto 4 speed packed to the brim  full of ports and heaps of unnecessary things women take with them. As this vehicle gets more k's on the speedo the fuel consumption appears to be improving, a friend said he also experienced this and best fuel consumption was at 80,000k

[DiogoASC]

I've tried to do the manual average by hand and didn't notice any big difference. I admit the odometer could be inacurate, next time I'll GPS track my usual motorway distance!

Thank you for the reply

[DiogoASC]

I also noticed a small decrease in consumption when I changed the rear tyres from The original Hankook to the Goodyear's eagle F1 (about 0,3 L/100km).

[Dazzler]

I also noticed a small decrease in consumption when I changed the rear tires from The original Hankook to the Goodyear's eagle F1 (about 0,3 L/100km).

That seems quite a lot to me for just changing two tyres!

[DiogoASC]

I also found it strange... One odd thing about the hankooks was that at 115-125km/h they had an audible resonance sound, now almost gone. I suspect this sound will end when I change the 2 remaining.

[Phil №❶]

To start with, you won't achieve the expected economy figures traveling at speeds in excess of 100 kmh, period. Frontal air pressure is working against the engine at these speeds and there is nothing you can do about that, except slow down. Fuel consumption is best at around 80 kmh, where the air pressure is not as great, and has time to slip past the car efficiently, rather than be blasted out of the way. Air resistance encountered by moving vehicles is NOT linear, it is exponential. Of course 80 kmh is too slow for most people, so you have to sacrifice economy to shorten your trip time.

Check after driving, that all wheels are cool to touch and that there are no binding brakes etc.

Driving fast will increase the number of DPF regenerations due to the increased amount of exhaust gasses emitted, caused by the wind resistance. This is normal.

[Asterix]

If your tires are noisy and the fuel consumption gets better after replacing the tires, I suspect the wheel alignment to be out of spec.

[DiogoASC]

They were noisy from the first day new....