Petrol versus Diesel

Submitted: Tuesday, Jan 25, 2005 at 21:30
ThreadID: 19773 Views:3902 Replies:10 FollowUps:26
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I am looking to buy a vehicle for a trip around Australia. Not being too mechanically minded one thing has got me completely confused. What is better - petrol v diesel? If one were to go for petrol is there something to watch for? Same question for diesel?

Some things I've heard - no idea if they are true or not:

Diesel is more expensive but you get better mileage
Diesel must have a turbo else it doesn't perform well

Your advice is appreciated

Cheers

John
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Reply By: Member - Nick (TAS) - Tuesday, Jan 25, 2005 at 21:57

Tuesday, Jan 25, 2005 at 21:57
DIESEL!!!
AnswerID: 94895

Follow Up By: zac_sprint - Wednesday, Jan 26, 2005 at 16:03

Wednesday, Jan 26, 2005 at 16:03
Diesel for an outback trip off the beaten track for sure but if you stick to the highway and major dirt tracks unleaded will get you there but will cost more.

I have travelled the outback in a sedan with LPG. LPG was very hard to get off the beaten track and expensive anywhere in the outback, but I did not have a problem except with kangaroos, horses, large bovines and of course the heat of the wet season.

but also have a read of
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for a detailed analysis of why some diesels are better than others
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Reply By: Bonz (Vic) - Tuesday, Jan 25, 2005 at 22:02

Tuesday, Jan 25, 2005 at 22:02
Diesel, hands down every time for this type of touring.

If you're touring around Australia then you wont mind loping along at 100kmh, and even a nonturbo diesel will do that, a turbo'd one will be that much better.

Diesel more expensive to purchase but better resale also, mileage isnt even comparable, diesel wins out there as well as fuel availability in some more remote parts of Oz. If you're going to stick to Highway 1 you can do that in a Falcon wagon. Get a diesel Falc if you can too ;)

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Follow Up By: Nick R - Wednesday, Jan 26, 2005 at 12:56

Wednesday, Jan 26, 2005 at 12:56
hey there,
Apparently some commodore engines bolt straight into a hilux (so I'm told) so I would love to do the opposite, bolt a diesel hilux engine into a commodore!!!
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Follow Up By: Chris (W.A.) - Wednesday, Jan 26, 2005 at 21:45

Wednesday, Jan 26, 2005 at 21:45
I'll admit i'm going for a diesel when my petrol craps but range isn't an issue.
I get 1200kms range out of a tank - did Gibb Road including Kalumburu and Mitchell Plateau without problem.

The canning stock route - the most remote in Australia, you need to order a fuel dropoff for diesel or petrol regardless.

It's all part of good planning as well - a roadhouse could be underwater and hence always phoning ahead to make sure they're open etc.

Diesel wins hands down towing which is the main reason I'm getting one.
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Reply By: Member - Jimbo (VIC) - Tuesday, Jan 25, 2005 at 22:11

Tuesday, Jan 25, 2005 at 22:11
If you want to get there eventually, get a diesel.

If you like to drive, get a petrol.

Petrol: more power and torque, but uses more fuel, as it should.

In the long run a petrol is cheaper; lower purchase price (and accordingly lower finance costs). Cheaper to service. Cheaper to repair.

If you like driving a bus, go diesel. If you like to drive a car, get a petrol.

Have a serious look at the power and torque outputs of comparitive vehicles; it tells a tale.

Cheers,

Jim
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Follow Up By: Member Eric - Wednesday, Jan 26, 2005 at 00:28

Wednesday, Jan 26, 2005 at 00:28
Sorry Jim , Yes more kw out of petrol but more torque out of a diesel mate
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Follow Up By: Member - Bernie. (Vic) - Wednesday, Jan 26, 2005 at 00:56

Wednesday, Jan 26, 2005 at 00:56
Come on Jim IMHO thats Crap
It can also have a lot to do with the choice of vehicle, tyre pressures & suspension etc
The Prado 3l TD is no sloush when it comes to get up and go & nothing like a BUS.

Cheers
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Follow Up By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 08:18

Wednesday, Jan 26, 2005 at 08:18
Bernie,

Prado GXL;

Petrol 179 kW, 343 Nm
TD, 96 kW, 343 Nm
and the TD weighs an additional 93 kg.

Please explain the "crap" comment.

Cheers,

Jim.
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Follow Up By: James M - Wednesday, Jan 26, 2005 at 09:05

Wednesday, Jan 26, 2005 at 09:05
Jimbo,

The torque may be the same. But what is important is how that torque curve sits.

The diesel would be lower and IMHO much better.

James.
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Follow Up By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 09:23

Wednesday, Jan 26, 2005 at 09:23
Sorry,

I made a mistake, the petrol Prado has 376 Nm, ie 33 more than the diesel.
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Follow Up By: Member Eric - Wednesday, Jan 26, 2005 at 09:42

Wednesday, Jan 26, 2005 at 09:42
Sorry Jim , your not comparing apples with apples , In the prado the TD is a 4 cylinder and the GXL runs a V6 with a larger capacity . The Petrol in the same capacity will always have more kw but the diesel will always have more torque. For starters the Petrol will be running something like 9:1 comp ratio & and the diesel will be running something like 15:1 . This is because the diesel engine has to compress the air in the combustion chamber till its hot enought to ignite the diesel when its injected into the combustion chamber at top dead center .

Cheers mate , hope this helps
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Follow Up By: Bob of KAOS - Wednesday, Jan 26, 2005 at 10:01

Wednesday, Jan 26, 2005 at 10:01
The Prado is a bad example as it has the least sophisticated diesel of any of the current offerings. Go and drive a few before you decide. Some of the modern diesels have brilliant performance and drivability. The Disco lopes along at low revs, takes hills without kicking down, and uses very little fuel. I've got a petrol too (LX470), but I prefer the diesel.
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Follow Up By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 10:04

Wednesday, Jan 26, 2005 at 10:04
Eric,

I fully understand how diesels operate. I think you''ll find the fuel is injected before the piston hits TDC to allow the compression to make it ignite. If it is injected at TDC it is introduced as the piston is about to go down and compression is reducing. The fuel cannot be compressed if it is injected at TDC. Similar to timing in petrol engines that fire the spark at a few degrees before TDC to ensure maximum burn as the piston hits TDC to give it maximum downward thrust, thus the term that this is the "power" stroke of the 4 strokes.

Now as for Apples v Apples. Toyota offers two engine variants in the same vehicle at about the same price. That is the comparison and the petrol offers more power and torque for the same money.

See you at Murray Sunset.

Cheers Mate,

Jim.
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Follow Up By: Member Eric - Wednesday, Jan 26, 2005 at 10:15

Wednesday, Jan 26, 2005 at 10:15
on the TDC , I was keeping it simple . if you realy want me to go into the tec , i can , but will bore most readers . Yes the 120 prado does cost the same for diesel td and petrol , but its not the same engine.

You initialy said , petrol has more torque than diesel , this is incorect , thats my point.

Yes i undestand the power princibles, now to keep it simple for some readers . Once you have momentum , kw are great . Heavy load , torque rules , yes its slow but you can strap 3 ton on a diesel and it will pull , slow , but will pull
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Follow Up By: Mad Dog (Victoria) - Wednesday, Jan 26, 2005 at 10:35

Wednesday, Jan 26, 2005 at 10:35
Eric, comparing a TD with a naturally aspirated petrol isn't comparing apples with apples. Compare a good TD with a similar capacity good TP
with similar boost and see what happens. The petrol will blow the diesel away on both power and torque and have a better torque curve....no contest!
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Follow Up By: Member - Bernie. (Vic) - Wednesday, Jan 26, 2005 at 11:08

Wednesday, Jan 26, 2005 at 11:08
Hi Jim
I just disagree with your comment all "diesels drive like a bus"
sure it may smell like one.
At the end of the day Stanno is going touring not racing.

Cheers & safe travelling
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Follow Up By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 11:13

Wednesday, Jan 26, 2005 at 11:13
Excellent point Ray,

The only two engines of identical capacity, that I can find, were the 4.2's fitted to GQ Patrols. Both 4169 cc and identical bore and stroke.

Diesel 85kW, 264 Nm
Petrol (Carburetted) 125 kW, 325 Nm.

No naturally aspirated diesel can match the power and torque of the same capacity and technology petrol.

Jim.
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Follow Up By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 11:36

Wednesday, Jan 26, 2005 at 11:36
Fair point Bernie.

Not suggesting they drive like a bus, I was just making an exaggerated comment about their relative performance. I realise many modern diesels have quite adequate performance to suit many peoples needs. I guess I'm still a bit of a boy racer at heart and just like that little bit of extra urge.

Cheers,

Jim.
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Reply By: ianmc - Tuesday, Jan 25, 2005 at 23:24

Tuesday, Jan 25, 2005 at 23:24
Hey get real Jimbo!

Paj 3.5 P 303nm torque
" 3.2d 373nm
Jeep 4.0P 295
2.7dt400
LC4.7P 410
4.2td 430
and the daddy of them all:
VW 4.2P 410nm
4.9td 750nm

Sure the petrols have more high speed power but only at higher revs & the fuel difference over big kms is most significant. Maintenance to me seemed to be lower on lower tech TD than petrols but now high tech may have changed that.

To each his own I guess.
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Follow Up By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 08:46

Wednesday, Jan 26, 2005 at 08:46
Ian you have chosen vehicles to support your view and I could easily choose some to counter that view.

You have neglected to consider kW's. It is the balance between Nm and kW that equates to perormance. Torque alone means nothing.

Cheers,

Jim.
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Reply By: old-plodder - Tuesday, Jan 25, 2005 at 23:27

Tuesday, Jan 25, 2005 at 23:27
Thnaks for clarifying why my diesel pajero (2.8l) is faster tham my old petrol pajero (2.6l). It isn't the disel at all, even though it has 20kw and 100nm more.
Must be something else. My diesel is'nt faster on take off either, that is why the petrol ones don't catch me until they have 4000 rpm or more on the tacho, and why they are one gear lower up hills. :-)

Will have to look for that magical petrol motor that makes the difference. :-).

Funny about petrols getting 100km less per tank.

And I don't even have a funny electrical box to tell the engine what to do.
(Theo at birdsville reckons half of the breakdowns in the Simpson are computer chips going on holiday as well.)

Love these debates about petrol versus diesel. Almost as black and white as nissan versus that other make.

Diesel is more expensive at the moment in the big cities, about the same in the country.

Read an article that bosch suggest that 80kw/litre will standard diesel outputs in about 5 years. Yes, 240kw from 3 litres. What is the max torque figure from the 4 something litre diesel VW toureg, 750nm? Can't be a diesel. Must be a petrol!
Diesels don't produce power, or do they?

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Follow Up By: Mad Dog (Victoria) - Wednesday, Jan 26, 2005 at 01:13

Wednesday, Jan 26, 2005 at 01:13
They can and do with a turbo but then they chew the juice....the reports I've read for the v8 Touareg are in the 17L/100K region
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Follow Up By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 08:40

Wednesday, Jan 26, 2005 at 08:40
O/P,

Comparing an antique (2.6L) petrol with a reasonably modern diesel (2.8) is not a real comparison. Mitsubishi's Equivalent petrol motorat the time was a 3.5 litre job. The 2.6 wasn't available in the Paj when the 2.8L T/D was about.

Apples with Apples?

Cheers,

JIm.
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Follow Up By: Mad Dog (Victoria) - Wednesday, Jan 26, 2005 at 09:13

Wednesday, Jan 26, 2005 at 09:13
Forget what I said. I should have been in bed :)
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Reply By: Crackles - Tuesday, Jan 25, 2005 at 23:34

Tuesday, Jan 25, 2005 at 23:34
Depends entirely on the type of car you are looking at. eg: a petrol V8 Discovery will use nearly twice as much fuel as a TD5 but the new petrol Prado isn't far behind the turbo diesel. For the big trips (Canning) a diesel doesn't need to carry as much which can be a problem for some petrols. (Where do you put 300Litres?)
I have an non turboed cruiser which although is slow at times will go everywhere a petrol will. If the bank account allows, a turbo diesel probably makes the best outback touring vehicle. If you do go for petrol the only thing to watch out for is that a few Aboriginal communities no longer sell it because of sniffing.
Cheers Craig.............
HZJ105
AnswerID: 94922

Follow Up By: Member Eric - Wednesday, Jan 26, 2005 at 00:31

Wednesday, Jan 26, 2005 at 00:31
lets not go with the non turbo will go everywere a petrol will lol . Touring yes , hard core off road , well . lets just leave the non turbo at home

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Follow Up By: Crackles - Wednesday, Jan 26, 2005 at 18:15

Wednesday, Jan 26, 2005 at 18:15
Followed Mike Smith (out back challenge winner) up a seriously hard core track he called "Sweaty Palms" 2 weeks ago without winching so the old 1HZ non turboed diesel is still pretty capable. When I said they will go anywhere a petrol will go I meant in the context of an around Oz trip which I believe was the question Stanno was asking. (Not many around Australia tourists take in the winch challenges) A petrol may do it easier but I find no matter how remote or difficult a track I always pass you lot at the bowser;-) Any particular tracks in Oz you think a standard diesel can't go where a petrol will?
Cheers Craig......
HZJ105 Tortoise vs Hare.
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Follow Up By: Member Eric - Wednesday, Jan 26, 2005 at 18:23

Wednesday, Jan 26, 2005 at 18:23
Come along on our next day trip . can show you plenty , Member John was with us last winter when we proved the same thing to a non turbo Nissan last year . Went home like a little sook he did
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Follow Up By: Crackles - Wednesday, Jan 26, 2005 at 21:56

Wednesday, Jan 26, 2005 at 21:56
Just took a look at your member pics. Nice shot in the mud. (Otways??) I must conceed that's where mine looses out on steep slippery hills even with the lockers in. Not enough momentum to get up :( But worth giving a go anyway.
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Follow Up By: Member Eric - Wednesday, Jan 26, 2005 at 22:38

Wednesday, Jan 26, 2005 at 22:38
That shot was taken in Gembrook , when we took Willem out for a day trip
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Follow Up By: Crackles - Wednesday, Jan 26, 2005 at 22:48

Wednesday, Jan 26, 2005 at 22:48
Holes up there too big for my 285s. Need 35" Simex to reach the bottom;-)
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Reply By: Member - Jimbo (VIC) - Wednesday, Jan 26, 2005 at 09:01

Wednesday, Jan 26, 2005 at 09:01
John,

Sorry, we have hijacked your thread by exchanging our various opinions.

I suggest this. Drive a petrol and a diesel equivalent of the same vehicle to compare. Do some things like nail it at 80 km/h to see how long it would overtake in each vehicle, use a stopwatch if necessary. See which responds better in traffic (this is where you will spend a lot of time).

The argument about torque is largely immaterial. It is a combination of power and torque that relates to performance and driveabilty.

Work out your overall cost to determine which is cheaper to run (purchase price, finance costs, servicing, repairs, cost of fuel, depreciation etc). You'll find there's not much in it; on the numbers I've done petrols usually work out a little cheaper overall, but others may disagree. There isn't a significant saving either way.

Good Luck,

Jim.
AnswerID: 94953

Reply By: warthog - Wednesday, Jan 26, 2005 at 12:31

Wednesday, Jan 26, 2005 at 12:31
john
I assume you will be considering a large vehicle for your trip around Aust in order to cart the inevitable odds and ends we feel we must take. These weigh 2000-2500kg empty. Loaded and fueled easily over 3000kg. A considerable amount of torque is required to shift this weight. It is the delivery of high torque at low revs that is a major factor in the better fuel efficiecy/driveability of a diesel. Offroading and increasing weight amplifys this advantage (almost anything that moves a considerable weight has a diesel engine).
I have a friend who has a 4.2 petrol gq, about 2400kg empty. The previous owner converted to gas, replacing the main the main tank with a gas cylinder, in an effort to reduce his fuel bill. The sub tank has been replaced with an 80 ltr petrol unit. Due to the thirst of the vehicle, the absence of gas in remote areas and reduced availability of unleaded, he feels restricted in the trips he can plan unless he removes the gas for these trips and puts a large main fuel tank back in. The fuel bill is going to be a major cost on your trip and when considering your choice of vehicle gas is not a viable option if heading of the blacktop.
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Reply By: Member - Davoe (WA) - Wednesday, Jan 26, 2005 at 14:24

Wednesday, Jan 26, 2005 at 14:24
For starters you have not said if you are looking new or second hand, Wheather you are toeing and what your power expectations are. I have driven nothing but normally aspirated diesal tojos for years now and I am very happy with the way my 80 series goes but you would consider it a slug by some standards. my 2c worth is diesal for there reliability, and economy but at the end of the day the reason why this post will generate plenty of followups is coz it is a personell choice so you will have to drive both.
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Reply By: Chris (W.A.) - Wednesday, Jan 26, 2005 at 21:38

Wednesday, Jan 26, 2005 at 21:38
Stanno,

I have a petrol cruiser and it does suck more than a diesel.

I've done the Gibb Road and up to Mitchell Plateau/Kalumburu and never had a problem with petrol supply. My 250L gets me 1200 - 1300kms where as a diesel in the equivalent may do about 2000kms - a fairly big difference but I've to find a more challenging place in Australia to drive 1200kms without finding fuel.

Even the Canning Stock Route do petrol/diesel dumps on it if you book them.
Diesel more expensive to maintain but must be to ensure that you get maximum mileage.

I'm putting a diesel in my cruiser when the time arrives because when it comes down to it I think the diesel cruiser is 17L/100km compared to 20L/100km for a petrol.

Regards
AnswerID: 95033

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