Poor fuel consumption on a new Kia Rio diesel

ItsOnlyMe wrote: »

Thanks for replies.
You seem to have cleared up that 'new car requiring run in' is not a myth, which I thought with modern technology was no longer required.

It is not strictly " running in " that was a period of gentle use in the first few hundred or so miles, in days gone by, it is really wearing in, modern vehicles are made to very tight specifications, and they don't loosen up fully until around the 4/5000 mile mark in my experience.

Things should improve with miles..

50mpg is good for a new engine diesel. If you're comparing your mpg with the manufacturers/EU stated mpg then you really need to knock 10mpg off their figures to be realistic. I'm fairly sure that the EU mpg test is held on a rolling road in a warehouse with no wind resistance!

I think the points have been made above now. Expect to fall short of official combined figures by possibly as much as 8%-10% anyway. If you do get the official combined figure (I almost am on my 34,000 mile diesel with similar driving conditions to you) it is likely to be in outside temperatures of around 10-17DegC when no heaters or aircon is required.
38mpg (winter and urban driving) to 53mpg (spring and casual motorway driving) is the range I see.
You need more miles on the car before you start measuring MPG.
Now that you are past the initial 1000 miles make sure you get the revs up near the red line several times a week to loosen the engine up so it can reach it's best performance and economy in time and not become a real oil burner.
In the first 8000 miles or so, as suggested above, watch the oil level like a hawk (every 1000 miles). Mine oil level went - 1000 miles on max, 3000 miles on max, 4000 miles on max, 6000 miles just below minimum!!!! All checks done on the flat with a cold engine. This is a fairly well known phenomena. My car uses hardly any oil now.

I think if you can get 55mpg out of it when you have 8000 miles and the right weather you will be doing well. You will probably notice the engine loosen up and improve a bit more as you go through the 10,000 to 20,000 miles range.

Also use BP Ultimate Diesel if you can find it no more than 6% more expensive than regular diesel. Millers Diesel Sport 4 additive in regular diesel is a good alternative (I've been using it for quite a while now.)