4.2 V8 - Real life fuel economy
 

Even though car is fitted with LPG, I think everyone can agree they run better on unleaded. So filled the tank up with premium unleaded just to see what milage I can get out of it.

Just wondering what sorta figures people get out of their V8s? I can't seem to be breaking 25 mpg at any point really, town or motorway.

Seems quite low, D2 4.2 I had previously would do 30 mpg quite easily on motorway, just want to make sure something isn't a miss and she runs as she should.

I average about 20 to 22mpg on my D2 S8, 14mpg around town and a little less than that on LPG.

I have never averaged 30mpg on mine, I can get there on the 2.8 D2 but not the S8.

I was averaging 15-16 on D2 S8 and 14-15 on S4 both 4.2. Would not see over 25 unless driving steady 50-60mph like through the roadworks on motorway

Being a bit OCD (aren’t we all?), I log every tank full of fuel on my cars so I can calculate the mpg accurately. I have 10 years worth of data on my D2 S8! The best I ever got (just twice) was a fraction over 23mpg. On a run, it’s closer to 20-22 and around the rural roads where I live it’s high teens.

Surely a long wheelbase version would be geared towards economy and causing compared to an S8? Long wheelbase D2 I had previously returned 27 mpg (full to empty) on mixed driving. Oh well, we'll see how the economy is when I go to fill up :rolleyes:

Fuel quality does make a difference. On Shell V-Power or Tesco's good stuff I'll get 25 - 26 on the motorway at a steady 70 ish. On my recent trip to Europe I filled up with 102 leaving Nurburg and got 26.7 with a fast trip 70 - 85.

I filled up with Sainsbury’s Super, and 65mph on cruise dash will be showing 22-23mpg which just seems low thus the post.

Although you've got a much more modern gearbox on the D3, the 4.2 isn't exactly torquey and you're probably lugging the equivalent of a couple of extra bodies around in kerb weight terms (Wikipedia isn't very helpful on D3 weights, but the lowest seems to be 150kg more than the lowest D2).

Wheels also make a massive difference, so if your D2 was rolling on small wheels and the D3 is on 20s that'll knock some off too.

Add in a couple of minor age related engine wear issues (worn injectors, fuel pump getting on a bit etc)

It's a lot of small differences that quickly add up.

Mike, as one of the key founding members, should really have a signature to show what car he has by now ;). The DIS display is usually pretty optimistic on fuel consumption so, unless you log petrol vs miles at regular fill ups, you’ll be dealing with Micky mouse data. i think high 20s on a 4.2 is a wish - unless you drive a puddin’. :p

BTW, I definitely get better mpg on V Power - almost enough to compensate for the extra cost. And I think that I’m probably the OCD guru on ‘real’ mpg data (long term and not DIS). But I rarely (maybe never) drive at a ‘steady’ 70-ish; perhaps a fairly steady-ish 80 or so, with a few aberrations! But I didn’t buy my S8s for fuel economy - I bought them ‘cos I love them and enjoy every mile. And my excuse for the running costs - I don’t play golf!