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What MPG are you getting...?


tjolliffe

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I'm sure this has been asked before but....what MPG are you getting?

I've got a 3.9 RRC on LPG and i've worked out that i'm getting just under 10mpg on gas - doesnt seem that great (yes I know its a V8 but even so...), especially annoying because it means the gas tanks are never big enough!

Any imput would be great, just want to see if what i'm getting is normal/abnormal?

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Under 10 on gas is about right? What are you guys smoking?!

On the motorway mine returns 20-22mpg on petrol, 18-20mpg on LPG.

Round town, of course it's a different story, 16-18 on petrol, 12.?-15 on LPG. Never got over 15 in town on gas for some reason.

That's 3.9 hotwire EFi, OMVL Millenium closed loop system. Engine is pretty standard, other than the camshaft, which is nothing wild, just puts the power band in a better palce for the autobox really. I have the ignition timing set at a compromise where it runs OK on both fuels, erring if anything on the LPG side. Probably in the 12-16 BTDC range.

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Had a 3.9 auto back in '02, LPG 14mpg (3.08miles/litre) on standard 205 road tyres, seemingly regardless of (on-road) useage. I don't drive any vehicle hard either.

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My 3.9 EFI Vogue has been on LPG since 2003

14 mpg in my experience is the average that I get and most other people.

The other point to consider is that LPG is only 70% efficient compared to petrol.

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Under 10 on gas is about right? What are you guys smoking?!

On the motorway mine returns 20-22mpg on petrol, 18-20mpg on LPG.

Round town, of course it's a different story, 16-18 on petrol, 12.?-15 on LPG. Never got over 15 in town on gas for some reason.

That's 3.9 hotwire EFi, OMVL Millenium closed loop system. Engine is pretty standard, other than the camshaft, which is nothing wild, just puts the power band in a better palce for the autobox really. I have the ignition timing set at a compromise where it runs OK on both fuels, erring if anything on the LPG side. Probably in the 12-16 BTDC range.

I agree, I only ran mine standard for about 4 weeks, but averaged 18-20mpg on petrol on a mix of town / open road. I never got round to fitting the LPG kit so can't comment there.

I'd say look at how your engine runs, ignition, mixtures airfilter etc.

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I'd be looking at what is killing the MPG too, things like tyres, roof racks, roll cages, bootful of carp etc is all going to really kill it.

Then there is the maintenance aspect: dizzy, timing, coil, ignition amp, leads, plugs, air filter, sticking calipers

Then if its higher mileage: Camshaft, head gasket failure (common into valley), worn cylinder walls.

If it is a standard vehicle on stock tyres and not on inter-galactic mileage then yes, 13-15mpg is about right.... on gas mixer system, a little more on a sequential.

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Thanks for the response guys. It's a totally standard rangey, 150k on the clock so wouldnt say its done LOADS of miles. Engine seems sweet no odd noises doesnt get hot ect.

It's open loop LPG so I know that doesnt help the MPG.

I've had a mess about with the mixture screw and managed to make it run quite a bit leaner and also advanced the timing so hopefully that'll help the MPG.

Guess i'll find out on the next fill up! :unsure:

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Making it leaner won't save fuel, just mean you are down on power and you have to put your foot down more to compensate = less efficient.

150K *is* a lot on a V8, they hide wear/noises well, but if it hasn't had a cam, then it is about twice overdue it! This is most likely your problem in all honesty.

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I got 14.5mpg according to the onboard electronics.

Thats was a run from Newton Aboot in Devon up to West Harptree and back, not being driven gently.

It was about what I expected for a 4.6 P38 with 230000 miles on the clock and BFG mud terrains fitted.

I get about the same round town normally. Managed to get up to 24mpg once but that was following a 110 towing a trailer with a 90 on it so driving extremely gently ( and boy was it boring!).

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Making it leaner won't save fuel, just mean you are down on power and you have to put your foot down more to compensate = less efficient.

150K *is* a lot on a V8, they hide wear/noises well, but if it hasn't had a cam, then it is about twice overdue it! This is most likely your problem in all honesty.

Surely if it was running too rich before then it was not burning all the fuel given to it hence - uneconomical. Wouldnt Making it run leaner compensate for this thus making it more efficient? I'm limited in my knowlage of V8's i'll admit but I thought that was the basic rule of thumb.... I've not noticed any real drop in power either.

As for the engine mileage, again, I dont know too much about V8's, only ever owned Tdi's but perhaps 150k on the clock is alot, i'm not too fussed though as the truck cost me next to nothing to buy so i'm happy to run it into the ground! :lol:

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Yeah, *IF* it was too rich before, maybe, but you have any proof of that? :)

Chuck your local garage(hopefully one with LPG knowledge) a fiver and get them to set it up on a gas analyser at idle and 3000rpm, that's all you can really do with closed loop systems :)

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I have just bought a P38 4lt 2001 with around 100k on the clock the shocking thing is the trip was recording 18.3mpg over the last 3000 miles which I was well happy with then this morning I must hve reset it which noticing or it automaticly does at 3000 miles thismorning it was averaging 21.5mpg which for my driving is a shock I assume it will droop back down to 18 again. the thing is I was assuming that it was so high because it had not adjusted to my flat out driving style and that in reality it was doing around 13mpg like my old one used to do so I didn't want to rest the trip meeter fearing the mpg would not be as good.(if any of that makes sence)

It goes for an LPG kit to be fitted at the end of the month as its my new daily driver from Southampton to Bournemouth everyday

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I have just bought a P38 4lt 2001 with around 100k on the clock the shocking thing is the trip was recording 18.3mpg over the last 3000 miles which I was well happy with then this morning I must hve reset it which noticing or it automaticly does at 3000 miles thismorning it was averaging 21.5mpg which for my driving is a shock I assume it will droop back down to 18 again. the thing is I was assuming that it was so high because it had not adjusted to my flat out driving style and that in reality it was doing around 13mpg like my old one used to do so I didn't want to rest the trip meeter fearing the mpg would not be as good.(if any of that makes sence)

It goes for an LPG kit to be fitted at the end of the month as its my new daily driver from Southampton to Bournemouth everyday

My 2000 P38 4.6 with about 99k on the clock varies depending on what sort of journey I'm doing. Certainly I can see (from a reset) up to 26 miles per gallon if I'm simply doing clear motorway work and on a reasonable 28 mile commute (combined local and motorway work) I tend to average out at about 19.5 over a period of a week doing nothing aside from the commute.

I did fit an ITG Maxgen Airfilter in place of the original and this seemed to improve consumption by up to 10%.

Round town it tends to be closer to 15mpg - and towing the horse trailer (laden) means the average falls to 10 to 14 (again depending on whether this is short or more sustained distance work) which I'm still quite happy with (or at least was before petrol went over the 120p per litre price.)

I still tend to think the V8 burns fuel as a function of time rather than anything else (though maybe this isn't the case if you travel at 70mph rather than 65!)

I have been reluctant to go to gas because of the up front cost, but I'm beginning to think again about this - however if it means falling from say 19 to 10 MPG for the commute then the benefit is maybe not so good. I'd be interested to know what you get after you gas yours! Keep us updated.

Thanks

Martin

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I've had a mess about with the mixture screw and managed to make it run quite a bit leaner and also advanced the timing so hopefully that'll help the MPG.

Guess i'll find out on the next fill up! :unsure:

The outfit that fitted my LPG (never again!) system warned against 'leaning' the mixture as the combustion chamber temp. with this stuff is high enough as it is. I'm going to upset some people now I know, but why are so many RR V8 owners so obsessed with mileage returns? You know that a 2 tonne, perm 4X4 with a V8 & auto-box is going to drink (lets not pretend that LPG conversions are carried out for the sake of the enviroment) so if you can't afford to run it, stick to a hatchback. If some owners sat down & worked out the true long term costs of their conversions they would discover that 'half-price' motoring promises are in fact a myth.

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Long term.... I paid £200 for my LPG system on my Range, fitted it myself, swapped it between my old range and new one, did about 15,000 miles on it.

Petrol, 14-15mpg, gas was 12-13, at the prices when I was running LPG it was 50% (or less at times) of the cost of petrol, so it was the difference between getting 14mpg, or the equivalent of 24-26mpg, based on cost per mile.

That was with mud tyres etc though ^^

So not quite half price, but damned close to it(!), and frankly anything that allows a V8 rumble on a budget is fantastic  :lol:

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Miles per gallon :blink: this sounds like a diseasal owners conversation :lol:

In all seriousness though, i'm getting about 9.5 mpg from my 4.6 90" with 35" tyres. Thats when i enjoy it :P If i'm boring and hold the traffic up and drive it like a diesel series towing 4 tons then i get 15- 18mpg out of it. I just accept it uses fuel like no tomorrow and fill it up when it's empty (kin expensive at the moment tho :unsure: )

Steve

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WTF!!! How does anyone get more than 15MPG from a V8 of any capacity?? Do you all drive like nuns ?? :o

My 3.9 Ninety auto with 255/85 MTs does about 10-11 MPG (on gas) on general run around work, the same gas MPG as my RRC with same power/drive train but standard road tyres. The Rangey can manage 14-ish on a run if I stick below 70MPH.

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WTF!!! How does anyone get more than 15MPG from a V8 of any capacity?? Do you all drive like nuns ?? :o

My 3.9 Ninety auto with 255/85 MTs does about 10-11 MPG (on gas) on general run around work, the same gas MPG as my RRC with same power/drive train but standard road tyres. The Rangey can manage 14-ish on a run if I stick below 70MPH.

My 3.9 auto used to return about the same on a long run with 20-21 on petrol & this with a mixture of 70-75mph on m/ways & 50-60 on A roads. I don't 'drive like a nun' but neither do I drive like a certain TV presenter!

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