58.2 MPG!!

[MarkyM]

Many may know that I had my XK8 converted but i've not hd a chance to give it an economy run.

My car is slighly modified so as to eek the best possible fuel economy (as I do 20k miles per annum) and the gas conversion was the icing on the cake...mods are:

Nitrogen in tyres
Straight through exhaust (doesn't wrap around rear axle) wit two boxes
Auto-RX engine treatment
Motorvac carbonclean (top end fuel system cleaner)
Professionally cleaned and calibrated injectors
Apexi air intake
Royal Purple 5w30 fully synthetic oil

I did a 350 mile run leaving late on Tuesday at 10 degrees C when I'd completed 185 miles without stopping the trip computer told me that I'd acheived 37.8MPG (but then that's linked to to standard fuel system). then 165 miles back (through London as opposed to around it) yesterday evening..traffic was heavier and LPG ran out after 305 miles (when it reverted back to unleaded). On arrival average fuel read at 34.3 MPG.

When I gassed up today the LPG tank took 56 litres and cost me £22.40, given that unleaded costs on average 94 pence per litre I worked out that to travel the same miles at the same cost on unleaded I'd have had to be achieving 58.2 MPG

Sad huh?

Since 29 MPG is what I think most people would achieve on unleaded for that type of drive it really is half price motoring!!

Oh average speed was 60 MPG...but then there were a lot of roadworks, speed restrictions and average speed checks M5/M4/M25

Regards

Mark

[MarkyM]

I've just completed an identical 350 mile run

2nd time around LPG ran out at 315 miles which would have meant over 60 MPG but local LPG supplier has increased price to 43p (from 40) which meant MPG effectively stayed the same at 58.2

Ideal conditions as journeys madelate or V early (4am) and hardly any braking, however due to roadworks, average speed checks and camera's (M5/M4/M25/A406) average sped was for second trip.

Trip comp (which obviously still calculates on unleaded was reading an average of 35.1 over the two journeys

With unleaded now at an average price of 98 pence per litre it really is half price motoring...even taking the lower calorific value and lower MPG into consideration.

I'd highly recommend it to anyone who does high mileage in their XK8/R

The company I used was gaspoweruk (www.gaspoweruk.co.uk based in Exeter and their aftersales care is superb.

Regards

Mark

[mike020150]

Good stuff Mark. Very impressive. Mike.

[MarkyM]

Last and final run

full LPG tank ran out at 310 miles
Trip computer read 34.4 MPG
Average speed 59 MPH
Refil 58 litres
Cost £23.14 (39.9ppl)

If I'd have used the same monetary value of petrol it would have been 5.2 gallons. since my local ASDa now does LPG at 39.9ppl it's great!

= 59.61 MPG

Oh I should have said that on all 3 journeys the car was fully laden on one leg (400lbs) driver passenger luggage, shopping & a dog!

Regards

Mark

[MarkyM]

I filled up from empty at a Flogas depot near Solihull on Monday which sells the cheapest LPG in the UK at 36.5ppl & covered 322 miles until my LPG ran out.

For comparison with unleaded costing £4.46 per gallon £21.32 would have bought me 4.78 gallons with 322 miles covered that's 67 MPG!!

Deep joy!!


Oh, I was only passing through the West Mids but anyone that owns a Jag there (or Doncaster where prices are similarly low) should consider an LPG conversion as you've got the cheapest LPG prices in the country

Regards

Mark

[Sid]

I really need to get my gas system looked at.
A full tank (£24) gives me about 150 miles.
Something definately not right there!

I have an AG system which was fitted by Nicholson McLaren Engines.

Seen a couple of places in Milton Keynes who service the AG system.
Hope I get this sort of mileage afterwards!

[MarkyM]

Sid, if you haven't got a multipoint sequential vapour injection system your never going to achieve similar mileage to me.

How much did you pay for your system and how long ago was it done? Mines a 60lt fill tank.

If more than 2yrs or less than £2000+VAT then you'll have a much older system which isn't capable of delivering 300 miles on a tank.

Regs

Mark

[Sid]

That will explain it. The system is 5 yrs old. Now needs its 5 yr service.
Will be much older. I dont get more than 200 miles on a full tank which I would guess is not much more than 40 litres. Cost to fill is around £22-£24 and LPG is 56.6 per litre (have seen it at 49.9!).

I've actually only managed to get 200 miles once! Its usually more like 170/180.

[MarkyM]

Sid I did a write up in Jan's JEC mag.

It doesn't sound like you do high miles like me (circa 15k miles per annum) so maybe not worth getting your system upgraded.

All I can say is that my install has already paid for itself after less than a year. With unleaded at £1.04 per liter and LPG at 0.47ppl it's less than half price.

Annoyingly is the price increase in LPG in the last year from 35ppl up to around 50ppl. Strange that there is a surplus of it (since it's a bi-product) and the govt have confirmed that duty wouldn't rise more than 1ppl per year from 20007-2010. so it's the middle men getting greedy

No matter...incidentally where do you have the filler, I opted for a lower bumper fill as not to ruin the beautiful lines (and cut the bodywork)

You can see a pic of mine on the gallery.

M

[Sid]

I do about the same mileage as you.
The tank has replaced the spare wheel and the filler is in the rear bumper same as yours!
A little cap which comes off the midle of the rear bumper. Same colour and very well fitted. Looks like it was factory done. No need to worry about which side the pump is on!

Its due the five year service soon so I'll have a chat with the guys then. With it already in place perhaps an upgrade wont cost too much.

[D_Doran]

Sorry I haven't read all the thread cos it's middle of the night!!!! Can anyone tell me if your annual road tax is less if you convert the car to LPG? Looking at it as a possible option... getting 22.8mpg on unleaded at 104.9p per litre and the local garage is doing lpg at 48.5 per litre, so want to see how long it will take to break even.

[MarkyM]

So little as to make no difference (I think £15-£25 per annum) if the VED reduction is the only reason your considering it then don't bother... I've never claimed mine.

As you've stated the price is less than half so that should be the determining factor. Personally I'd say if your covering less than 15k miles per annum leave the car as it is.

Other advantages

1) I've never known LPG out of stock
2) There's no one ever at the LPG pump (so faster fill-up)
3) It brings a BIG smile to your face knwing 300 miles of driving has only cost you £28 in fuel
4) Your oil stays clean (no carbon deposits)
5) The switch-over to gas indicates that your engine is at the right temp for driving..wherever possible you should never drive an engine away from cold as there is no lubrication protection (oil hasn't circulated) whether converted or not.

Remember that you still need to start in petrol but a full tank of Shell V power or Tesco's 100 RON typically lasts me 5-6 months. I'd always go with the higher octane fuel as petrol degrades over time.

Regards

Mark

[D_Doran]

Thanks for that Mark. I'm doing about 10k miles per year at present, but I am seriously considering the change anyway. Just got to sit down and do the maths to see how long before I break even, but the way the fuel costs are going at present, that time is certainly reducing!

[D_Doran]

Well it looks as though I am about to follow Mark's lead and join the LPG converted club!

The system I will be getting fitted to my 2002 4.0l XK8 is a Romano Multi-point Sequential Vapour Injection System.

The filler is going to be hidden low on the right hand side of the bumper where the towing eye is located. We are hoping to be able to use the cover again, so it will not even be obvious that the filler is there! I will lose the towing eye, but don't ever expect to use it anyway.

The lpg/petrol switch and gauge will be mounted alongside the valet switch beside the drivers right knee where there is a vacant position for a switch anyway.

I am most likely going to keep the space-saver tyre in the boot (in a 'tyre bag') as I am worried that using the tyre puncture repair spray may actually do more damage to the tyre, and you know just how expensive they are!

The job is scheduled to be done over 4 days starting June 7th, and I have asked that they take pictures at each stage, so I'll post them in the gallery for everyone to see.

Damian

[MarkyM]

Damian

Good luck and I hope it all goes well...potentially a great time to get it done

Unleaded £1.12 per litre
LPG £0.50ppl

Ensure that you fit a set of iridium plugs and if possible switch to 5w30 fully synthetic as I noticed a 10%+ range increase after doing these basics.

Mark