What MPG should I expect from my V8 Discovery?

[Fuzzy's Series3]

As per the title really? I run it on LPG and am certain that it is using WAY too much fuel. I only get around 10 MPG from LPG, I don't really run it enough on petrol to know what kind of figure I get.

What sort of MPG should I expect from it? Most of the time I use it for journeys of medium length-I am just after an average sort of figure that I should expect as I am fairly sure that even for a 3.9 V8 I should expect more than that!

I have the vehicle booked in for a service of the LPG system, the chap reckons this is the most likely reason for the poor fuel economy. If this doesn't fix it what other likely causes are there? Lambda sesnsors have been suggested, are there any other places I should be looking?

Thanks in advance!

[sniff my diff]

, are there any other places I should be looking?

Bank manager for a bigger over draft???
I would have thought around town 12-15mpg and on a long run 18-22 on a good day ... but i will prob be corrected

[V8_Disco]

I have a later 4.0, I get between 13 - 16 MPG on gas

how meny miles has the engine done?

Aidan

[MarkWillenbrock]

Any big petrol V8 in a heavy car will be terrible around town or on short, stop start journeys with a cold engine. I've had all sorts of them, including several V8 Range Rovers, and single figure mpg is easily achieved.

I've never had a 3.9 V8 Disco, but the following might be interesting. I do measure mpg properly, brim to brim, except where there's a computer on the dash.

1982 4 speed Monteverdi V8 carb - 18 to 20mpg on a run.

1984 5 speed Vogue V8 carb - the same.

1985 Vogue EFi auto - 15 to 20mpg

1993 Vogue LSE (4.2 EFi) 16.7mpg even at a cruise controlled 75mph!

1996 P38 4.0 SE 16.8mpg after a 68mph cruise controlled run from SW France to London via Venice!

They are thirsty! My sadly missed Bentley Turbo R, all 6.75 litres of it, was more economical on a motorway run.

LPG seems to knock MPG badly. At one stage I had two near identical Jaguar XJ6 2.9s, both with manual boxes, but one with LPG and one without.

The LPG equipped car was so much more thirsty they cost the same to run. I admit this was on London to Edinburgh motorway work, with lots of wide throttle. The LPG car was also much slower, which meant it spent more time on full throttle. Even so, I was disapointed. I understand LPG has more of an advantage on part throttle.

[Fuzzy's Series3]

Hi all, thanks for the responses.

The engine has done 100,000 or there abouts so it hasn't got silly miles!

I know I used to get better MPG from it hence I am fairly sure something is wrong somewhere along the lines!

Sniff-if all else fails then I think the bank manager might be the best option!

[DeanV8]

My 4.0 DII is in tip top condition engine-wise, having just been completely rebuilt, and LPG system (fullly sequential) running best as possible, and when driven with a reasonably enthusiastic right foot it does 10mpg on gas and petrol.

This is pretty much all you can expect - my 4.0 P38 does 12mpg, but it's on a single point LPG - and doesn't "go" anywhere near as well as the Disco.

Unfortunately, if you're bothered about fuel consumption, a big Rover V8 is the wrong vehicle to own.....

Cheers

Dean

[littlelegs]

LPG has a lower calorific value per litre than petrol so will return lower MPG. This is the same with LPG heating, people are often mislead and think it's cheaper than oil but it's likely to be 50% more expensive.

[Ogbyte]

We run two V8 Disco 300's on LPG (single point mixer type) - MPG is around 12 or so, with best being around 17-18 on long run to cornwall last year.

we get around 160-180 miles on full tank (73ltrs in one) and 200-250 in other (100ltrs)

cost of lpg to unleaded works out around twice amount lpg for each gallon unleaded works out at twice the MPG appx, so 24-36.

Looking at getting a D3 next, possibly diesel instead this time around (cost of LPG conversion outways fuel costs - around £2500 for decent multipoint system)

Gary

[littlelegs]

We run two V8 Disco 300's on LPG (single point mixer type) - MPG is around 12 or so, with best being around 17-18 on long run to cornwall last year.

we get around 160-180 miles on full tank (73ltrs in one) and 200-250 in other (100ltrs)

cost of lpg to unleaded works out around twice amount lpg for each gallon unleaded works out at twice the MPG appx, so 24-36.

Looking at getting a D3 next, possibly diesel instead this time around (cost of LPG conversion outways fuel costs - around £2500 for decent multipoint system)

Aside from needing to do a lot of miles to get back the conversion cost, the saving on the road is in the cheaper tax but with heating, LPG and oil are much the same but big difference in running cost per litre. My 300TDI easily returns 32MPG, that's 600 + miles to the tankfull on diesel all the time except when towing fast but actually got 35MPG @50MPH with the caravan in my old 200TDI. With veg oil normal running could be the equivalent of 40 - 45 MPG and a much cheaper conversion with a considerably longer range without a large additional tank, worth thinking about!

[qzdcg8]

Looking at getting a D3 next, possibly diesel instead this time around (cost of LPG conversion outways fuel costs - around £2500 for decent multipoint system)
Gary

I get between 21 and 28mpg out of my D3 2.7TDV6 Auto - others claim 30 out of a Manual. Sticking a G4 Expo Rack on it has NOT helped though - its running at 20.5 according to the Trip Computer now