Author Topic: 30 mpg on motorway driving.  (Read 762 times)

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  • scotland Scotland
    West Lothian
  • i30 1.6 CRDi SE NAV
30 mpg on motorway driving.
« March 18, 2018, 18:08:04 »
Since getting my new gen i30 diesel Iíve had it on motorway regularly and instant mpg is reading between 25 - 35 mpg. I know sometimes it may be doing a regen but surely not everyday. Beginning to drive me crazy. That is me driving at 65 mph with cruise on in 6th gear.


  • Hyundai i30 1.6 CRDi SE NAV 6 speed manual

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  • au Australia
Re: 30 mpg on motorway driving.
« Reply #1 : March 18, 2018, 19:30:24 »
How far do you drive? Could it be that you don't drive far enough to do a full regen so the car is constantly trying to do one?

Is the instant MPG that stupid gage thing that goes up and down depending on what you are doing with the car? What is the stable figure?
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Re: 30 mpg on motorway driving.
« Reply #2 : March 18, 2018, 19:48:11 »
If it was trying to regen, would'nt the DPF warning light not be coming on?
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Re: 30 mpg on motorway driving.
« Reply #3 : March 18, 2018, 20:02:20 »
The DPF warning light only comes after it has tried 3 regens which failed to complete before the end of the journey..

If the warning light comes on you take the car for a 20 minute blast on the motorway.  If that does not get rid of the warning light you go to the dealer for a forced regen - which you may well be charged for.

My suggestion would be for you to fill the tank to the brim - and I mean to the brim - so the fuel is visible and stationary in the filler neck. Note the odometer reading (miles) and reset to zero the average mpg in the trip computer.

Now use the car for at least 300 miles (the further the better) and then fill it to the brim again. Note the amount of fuel added, the mpg shown in the trip computer and the odometer reading. You now know how much fuel was used in the distance travelled from which you can calculate your exact mpg and compare it with the car's average mpg shown on the trip recorder.

This will confirm whether the trip computer is accurate. You may well have a dicky average mpg computer or a dicky instant mpg display rather than a DPF problem.


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  • Author
  • Posts: 58
  • scotland Scotland
    West Lothian
  • i30 1.6 CRDi SE NAV
Re: 30 mpg on motorway driving.
« Reply #4 : March 19, 2018, 04:41:59 »
Thanks guys, the car does not indicate when a regen is underway which is a bit frustrating, the only way I can tell is when the fuel consumption increases. Staying off the motorway on an 11.5 mile trip to work I can get 54 mpg going however it decreases to 45 mpg on the way back home. Exact same road and light to zero traffic.
On motorway driving my instant, average & accumulated consumption all decrease.
Iíve done approximately 1000 miles since getting the car and my average is 47.6 mpg and thatís me driving as economically as possible, would hate to think what Iíd get if I drove as Iíd like to.
I traded in the MK2 I30 crdi which was giving me about 50 mpg but I drove that one ďenthusiasticallyĒ
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Re: 30 mpg on motorway driving.
« Reply #5 : March 19, 2018, 14:44:43 »
I seem to recall you getting the car low mileage? Like 2500 miles low? In case that is true its not run in yet, my economy was down the drain  the first 15000km. The diesel also takes 10km to heat up or so, more if its cold.

Keep track of the consumption when you fill up (log odo and fuel vol) and you will see it get better.

I don't think it's the dpf - the increase in fuel consumption from regen is as far as I can tell very marginal. (the big decrease is from having it limiting exhaust in the first place). I can't tell tanks that have done two regens from the ones that didn't regen.

I post a fair amount here on the topic.
:link: Xiziz Log thread - Current record 3.96 l/100km
« Last Edit: March 20, 2018, 03:19:01 by xiziz » »
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  • scotland Scotland
    West Lothian
  • i30 1.6 CRDi SE NAV
Re: 30 mpg on motorway driving.
« Reply #6 : March 19, 2018, 17:37:22 »
Thank you XIZIZ, yes I got the car with 2150 miles on the clock and have now done about 1000 miles since. Fuel consumption seemed to be better today so Iíll just need to monitor it. I appreciate your help.
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