Petrol v's Gas

Submitted: Wednesday, Mar 09, 2005 at 20:23
ThreadID: 21101 Views:2326 Replies:7 FollowUps:7
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Hi all,
I am looking at getting a GQ and have a couple that look good, one is straight petrol the other is duel fuel, having never owned a car on gas I don't know the pros and cons, and I wonder although gas is cheaper do you get comparable km's out of a litre of gas as petrol?.
ps I know deisel would be good, but none around my area in my price range.
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Reply By: Member - Roachie (SA) - Wednesday, Mar 09, 2005 at 21:02

Wednesday, Mar 09, 2005 at 21:02
G'day Zach,
I had a 1990 Maverick from new which I owned for 5 years. It was petrol and after a couple of years I got it changed over to dual fuel. Not a good choice as far as I'm concerned. Later, being sick of missing/farting and compromised state of tune, I actually went further the wrong way and changed it over to total gas only. It ran much better, but my range was only about 320klm. If I'd had my time over I'd have left it as petrol only.....I doubt that the money I saved on gas was enough to off-set the cost of the 2 conversions (note the 2nd conversion to gas only involved a new carby replacement).
You will use about 20% more gas quantity over a given distance than you would use petrol and the lack of availability in some smaller towns in the bush was the chincher for me. I bought a 1993 GQ diesel.

IMHO you'd be better off looking a bit further afield and finding a good diesel; but I understand that the big oiler does not suit everybody. If you do buy a diesel, don't be tempted to get a 2.8 litre slug.


AnswerID: 101828

Reply By: muzzimbidgie - Wednesday, Mar 09, 2005 at 21:48

Wednesday, Mar 09, 2005 at 21:48
I agree. I owned an FJ62 (3F) on gas, which is similar to the GQ, in that it is a carbueretted motor, and it was always coughing and spluttering, and no matter who tuned it, it was never right. I replaced the carby, the distributor, and most other things involved with fuel or spark, to avail. I believe fuel injected motors go alright with gas.

Also, for the amount of fuel I carried, I was dissapointed with the distance I could travel. And as stated above, its totally useless when travelling to places where gas is not available.
AnswerID: 101837

Reply By: Boo - Wednesday, Mar 09, 2005 at 23:24

Wednesday, Mar 09, 2005 at 23:24
Evening... I've had 2 Falcons on dual fuel (gas and petrol) and couldnt praise them enough, they were both great. I now have a 4.2lt 93 GQ Patrol with the dual fuel, its the fuel injected model and it matches the Falcons as far as reliability and performance, as mentioned by Roachie the distance I also get on a tank of gas is also around 320 mark but still have the main petrol tank for when I'm somewhere that doesnt have the gas, which I use the Gas then as a backup and run on petrol. As for perfomance.. I find there is NO difference between the power I have when running on gas compared to running on petrol, may be because its slightly tuned in favour of the gas, not sure. I have found that with all the three different model vehicles I've run on dual fuel, its not more important that you have a good quality gas system fitted , one that can be adjusted and tuned (some cant) and that its a good reputable brand, (ask several different fitteres for their opinion as to which type and you'l find the better ones will give similar answers) some are computer controlled so you can fully adjust fuel flow etc, others are manually adjusted which dont have as fine adjustment and then the nasty ones are pre set which tend to give a lot of trouble. Not sure what it costs to add gas to a GQ but just priced having it put in my sons Falcon and it was around the $2700 for the computerised model and around $2500 for the manual model. In short ... check which are the better brands and compare them to whats already in the vehicle your looking at.
Personally I wouldnt have a thirsty vehicle like the Patrols without it.
AnswerID: 101862

Reply By: SenorHondo - Thursday, Mar 10, 2005 at 00:41

Thursday, Mar 10, 2005 at 00:41
I've had both a dual fuel GQ Maverick (to which I fitted the gas), and (currently) a GQ diesel (with aftermarket turbo). I wouldn't touch a dual fuel again with a 40 foot barge pole. It gave trouble (carby version), failed completely on Stockton Beach, and gave apalling consumption - eg 600 kms from a tank of diesel, 400 to 450 for petrol, and about 350 gas. Always seem to be at the service station with the gas - and its slow and tedious to fill. Oh, I nearly forgot - the petrol cracked the head - reason never fully confirmed, but my suspicion was, because gas runs hotter in combustion, the head cracked at a hot spot - and yes, I was running valve lube - that sure cleaned up any potential fuel savings!!

Also, diesel engine superior off road for engine braking. And to top it off, the turbo diesel had more performance than the petrol on gas, particularly torque.

If I had petrol, would not convert. Best to look for a diesel. You won't be sorry, and save up the additional for a turbo charger - would cost you about the same as a gas conversion, and better value for money in my opinion.

Additionally, I previously had two dual fuel Commodores. Similar story - more fuel, less performance, and troublesom to start - particularly on cold mornings. Think I would have learnt my lesson!! But for some of us it takes three lessons to learn the one true way!!
AnswerID: 101869

Follow Up By: Mad Dog (Australia) - Thursday, Mar 10, 2005 at 00:49

Thursday, Mar 10, 2005 at 00:49
Senorhondo, were the Commodores you had carby or injected ?
FollowupID: 359715

Follow Up By: SenorHondo - Thursday, Mar 10, 2005 at 07:18

Thursday, Mar 10, 2005 at 07:18
Mad Dog

One was a VN, fuel injected, and the second was the last of the VS model, again fuel injected (as they all were). It was better, and was fully computerised, but it was still temperamental on occasions, particularly if you stuffed up the morning starting ritual, or forgot to switch to petrol as you pulled into the driveway last thin, and was amazingly bad on consumption. Only about 350 from 80/90 litres on gas.

My view is to forget gas - a false economy, unless you are running a taxi 24/7.
FollowupID: 359721

Follow Up By: Mad Dog (Australia) - Thursday, Mar 10, 2005 at 11:35

Thursday, Mar 10, 2005 at 11:35
That's surprising because it always seems to be carb vehicles that have problems. I had 5 vehicles on gas, all injected apart from the hilux and all have been brilliant. My present AU is simply brilliant on both fuels, can't tell the difference between petrol and LPG. My Hilux while still being good is not quite as good as the AU but that's the diff between carby and injected. It starts and drives well on LPG from cold but will miss for a few minutes on petrol. LPG has saved me a small fortune over the years.
FollowupID: 359758

Follow Up By: SenorHondo - Thursday, Mar 10, 2005 at 22:50

Thursday, Mar 10, 2005 at 22:50

Commodores are known for problems on dual fuel, in particular blowing the cover off the aircleaner from backfires through the induction system. This is something to do with the timing of the spark/ignition through the plug pack. This isn't a problem for a petrol vehicle, but is on gas, in particular when starting the car for the first time for the day. When its running, all is fine, it is the starting that is the problem.

Anyway, after a number of failures and problems over a period of approximately 7 years of owning dual fuel vehicles, I swore off them for life. Certainly any cost savings were used up by the head failure on the Maverick, and they are known for this particular problem on gas (I found out later).

FollowupID: 359821

Reply By: Brew69(SA) - Thursday, Mar 10, 2005 at 07:34

Thursday, Mar 10, 2005 at 07:34
The thing everyone seems to be ignoring here is the cost of keeping them on the road. Petrol/Gas is at worst half the cost of running a diesel.If i could afford to run a diesel i would probably have one for supply problems u get was gas in remote areas. I have 115lt of usable gas which gets me between 420-550kms.(not achieved the better since roof rack installed.ave 450ish) Also have 70lt ulp belly tank which adds its not bad range but i will admit a diesel with long range tank will get u heaps further. What you need to do is work out where this vehicle will spend most of its time(road or bush?) If its bush then go with the diesel. As mine in doing 500kms a week in the city i would have to be a rich man to run a diesel. Gas is regularly 39.9c in the city and with the 4c off a tank costs approx $40.(cheaper to run than my 4cyl tarago was) Also servicing is every 10k not 5k. If you go with a carby dual fuel then i can not stress strongly enough to spend the 2 or 3 hundread dollars on fitting an electronic ignition as the tuning probs mentioned above will drive u crazy and this 100% fixes the problem. Hope this helps........always 2 sides to a coin.
AnswerID: 101876

Follow Up By: SenorHondo - Thursday, Mar 10, 2005 at 23:05

Thursday, Mar 10, 2005 at 23:05

Current fill price for a tank of diesel (long range tank in the GQ) is about $120, which will take me 800 kms around town, ie $15 per 100km. Compare that to 95 litres of gas for say $45, plus 70 litres of petrol for about $70 (being generous with pricing, but assuming $1 per litre). Total cost for that is $115, to travel 770 kms, a cost of $14.9 per 100km. Not much difference, really.

I realise, of course, that around town you would use 2 and a bit tanks of LPG to travel 800 kms, with a total cost of $100 or so. It isn't much of a difference really, compared to diesel. Of course, compared to a GQ petrol, it is much better. The need to have one or two additional services through a year for a diesel is not much of an expense, when you include the obvious benefits of improved off road performance, fuel availability anywhere in Australia, and lack of complications.

I still would go the diesel every time.

FollowupID: 359822

Follow Up By: Brew69(SA) - Friday, Mar 11, 2005 at 06:52

Friday, Mar 11, 2005 at 06:52
The comparison u are making here is only if both petrol and gas are required to get the range. If i travel 30 000 kms a year and lets say i can run gas for 25 000km then running costs have to be worthwhile . When running gas 115lt costs me $40 which does approx 450. so $10 worth of gas gets me about 112kms. ($8.90 /100km) Work that out over my 30 000kms a year and i am saving heaps. Your claim that i need $100 to do 800kms is wrong. $80 gets me the $120 you spend on diesel that gets you 800kms gets me 1350kms. (not much of a diff u say? :))
FollowupID: 359834

Follow Up By: Member - Jimbo (VIC) - Friday, Mar 11, 2005 at 12:03

Friday, Mar 11, 2005 at 12:03
One important point has been overlooked.

These figures are taken direct from Nissan,s specs in an old GQ brochure that I have.

Diesel 85 kW and 264 Nm
Carby Petrol 125 kW and 325 Nm.
Note the Petrol delivers more torque than the diesel at any given RPM.

I have driven both and the difference in performance is HUGE. The diesel is a very slow vehicle.

So for less money you get better performance with the LPG conversion.

As for "the obvious benefits of improved off road performance", I would seriously question that; how can a less powerful and less torquey engine be better off road? I've seen a diesel GQ stop halfway up a dune that I flew up in a humble Terracan.


FollowupID: 359861

Reply By: Member - Jimbo (VIC) - Thursday, Mar 10, 2005 at 09:57

Thursday, Mar 10, 2005 at 09:57

I had a GQ 3 litre petrol running on dual fuel. I found it used around 8% more on gas, and I put this down to me driving it harder and not being concerned about fuel cost. I couldn't notice any performance difference.

As for tuning; LPG has an octane rating of over 100 and ULP is 92. Therefore if it is tuned for LPG it will not run as well on petrol. I suggest tune it for LPG and run Optimax or similar which has octane rating of 98 when running on petrol.


AnswerID: 101900

Reply By: theshadows - Thursday, Mar 10, 2005 at 19:00

Thursday, Mar 10, 2005 at 19:00
well here is a postive for lpg.
My old 60 series was an 2f motor. I pulled a gas unit out of an old xc falcon taxi and popped into the cruiser.

Now I did the head up before I ran it with S/S valves and hardend seats and popped a new water pump in and it gave now problems to the chassis rusted away.

remember always tune it on petrol first. Then after you got the petrol sorted the adjust the mixture of the lpg to suit the petrol tune. NEVER tune it on lpg first the petrol side will never run properly.

the other good thing is running on lpg and you loose coolant you never seize the motor. the lpg convertor will freeze solid first. this has saved me from 2 blown motors.

but with all the problems and the hassle of the second tank..... let me say I drive an diesal now.

AnswerID: 101976

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