some people have replied on A5OC, is it a US based site? have they got very weak diesel over there?
the figures are appalling compared to the old mechanical TDI's.
is it really the case that they will only manage 40-50mpg on motorways?
if it is is this due to the DPF rubbish they fitted?
No it's predominately UK, but there are US and Australian members. I used to be very active on there a few years ago, but I don't post much anymore.
DPF 'rubbish' is a necessary exhaust filter needed downstream to stop extremely high levels of NOx, which has been linked to respiratory health problems. Whilst diesels provided an answer to reductions in CO2 compared to petrol, unfortunately they emitted much more NOx. In order to circumvent this, DPF's were introduced, but as regulations have become even tighter, there was also a need for things like AdBlue. Of course it also came to light that not only where VAG cheating emission's tests, so the real world emissions were much higher than stipulated, but even manufacturers who legitimately passed the emission tests were also emitting NOx levels much higher than the test values in real world driving. Even today many EU6 diesels have massive disparity between test values and real world values.
So while high MPG and low CO2 is great, it comes at the cost of high NOx and poor local air quality, with a lot of evidence suggesting this has very real consequences for people living in urban areas with things like COPD and other chronic lung conditions. As a result, DPFs are needed, but in order to keep that running well, it needs to regenerate at high operating temperatures.
So not only is there the economic argument regarding doing high miles with a diesel, there is also the practical argument that typically longer (although arguably the type of miles is actually more important, but obviously high miles and long motorway journeys often correlate highly..) journeys are necessary to ensure no costly repair bills.
I mean, if you do low miles, but have to spend once a week blasting down a motorway in a high gear just to keep the DPF in good condition, it sort of defeats the entire point about having high MPGs....!
Sorry bit of a essay....but 50MPG sounds reasonable to me...? I would expect about 20MPG difference?
And as i thought I already pointed out, it's such a minute cost saving that I still don't know why you place so much importance on this 'MPG' figure...sorry to be frank, but it's like you are chasing a really high MPG figure without much consideration to what it will actually mean in real world cost? Bit like concentrating on peak BHP output, when the reality is that an increase from 300BHP to 320BHP will unlikely be noticeable in real world driving!