Petrol (gas) or Diesel?

[Walkabout]

While following the threads in here I get an occasional feel about the preferences of owners for certain types of fuel - usually the obvious one about fuel economy (although quite surprisingly, to me, some owners say that their petrol vehicle gives better fuel economy than some other diesel vehicle).

So, my question is, what is your preferred fuel for overlanding/travelling distance?
If there is some kind of reasoning for your choice, which does not have to be entirely logical of course, then so much the better.

Personally, as a bike rider, I would always prefer to come across a petrol vehicle while travelling, for the opportunity to cadge some "essence" when my tank is low.

[oldbmw]

perhaps if you rode a diesel bike your perspective might change.

I prefer diesel as a fuel, as petrol is much more flammable and dangerous. I would never have petrol on the boats I built. Diesel is also much more frugal on fuel. A petrol engine always runs at about 14:1 fuel air ratio, but a diesel idling can go to 200:1

Again until the advent of electronics , there was very little that could go wrong with a diesel, usually if it started it would complete your journey and is completely impervious to damp.

[palace15]

Nice reply oldbmw. Never be afraid to run out of fuel with diesel, the Worlds economy runs on trucks...powered by diesel, the chances of scrounging a bit of diesel are far greater than petrol.
alot of small diesel bikes(400cc ish) are from stationary plant used for pumping/generating etc so also if you incured a problem 'fixers' in 3rd world countries would be more abundant than a mechanic who knows anything about a xtxrgxrr1 etc. With my 22litre tank on my Robin I either fill once per continent or every christmas!

[onlyMark]

"Never be afraid to run out of fuel with diesel" The problem with that is the bleeding bleeding to get it started again!
The petrol v diesel debate could go on and on but in practical terms, for me it only comes down to several factors.
Initial cost, servicing intervals, economy, availability of fuel and level of complexity.
Generally a newer diesel costs more than a newer petrol, you have to service a diesel more often, diesels are more economical, diesel fuel is more available that a high octane petrol, diesels are less complex.

I tend to prefer diesels as I can get further on a tank full, I can get diesel all over the place, I can more easily diagnose and fix the engine problem and there seems less to go wrong.
To live with those advantages I tend to swallow the fact that it might have cost me more to buy the vehicle in the first place and that I have to plan where/when I do the servicing more often.

In practical terms it doesn't bother me that petrol is more inflammable, that a diesel is more noisy, has less power and is not as smooth.
What does bother me is if I can't get the right grade of fuel for it, I can't go as far before I have to look for fuel and it's too complex for me to fix (or at least know what needs fixing).

[eightpot]

Something I noticed in Libya, where fuel deliveries were sporadic and huge queues formed at the filling stations, was that virtually every car was petrol. As they were waiting in queues 30 deep, and everyone would obviously fill thier car to the brim as well as any container they could find, it could be a day out topping up your tank.
If you were after diesel you could usually go straight to the seperate diesel pumps though with no queue.
The downside was that diesel was more expensive there, around a whopping 7p a litre, against only 5p for petrol.

[onlyMark]

I don't know why and I'm not sure of the facts, but I think some countries, like Egypt, banned the import of diesel cars for a long while (?) I'm told that is why there are so few of them here even though diesel is about half the price of petrol (diesel 7pence/litre, petrol 13pence/litre).

[m37charlie]

One advantage of diesel not yet mentioned: diesel worldwide will burn in an engine; whereas petrol is very low octane in many 3rd world countries and will quickly destroy a modern higher compression motor designed to run on what Europeans call "4 star" and Americans call "premium" petrol. Even motors designed to run on 1st world "regular" can't tolerate petrol from certain countries.
The only thing that will be destroyed in a new diesel (presuming the fuel is properly filtered) is the catalytic converter if so equipped; which can be disconnected before the trip or replaced afterwards.

Charlie

[gilghana1]

For many markets if you want a durable, workhorse 4x4 to use for trips then you actually have no choice and have to go diesel... Example - Landrover Defender has not been available for quite some time now (like years!) in the UK in a petrol version.

And to be honest with fuel costs and diesel availability as well as it being safer to mess around with extra fuel cans and tanks if they are full of diesel, I cannot really think of a good reason to run a petrol overland vehicle other than maybe to standardise to one fuel in a mixed car and bike expedition?

Gil

[Walkabout]

Originally Posted by gilghana1

I cannot really think of a good reason to run a petrol overland vehicle other than maybe to standardise to one fuel in a mixed car and bike expedition?
Gil

I had a similar thought but I guess the answer is to use a diesel "mothership" that carries jerry cans for the bikes.

I had wondered about the availability of diesel fuel viz a viz petrol: on the lines of "is it the same world-wide?"
My impression is that it is in universal usage for trucks nowadays. Is there any part of the world where this is not the case?

I've run a few diesel fuelled cars in the UK over the years and I used to be a convert to the fuel because I was running highish annual mileages: for "bog-standard" cars it is not such a clear cut view for me nowadays.
In the UK the capital cost of purchasing a diesel engined vehicle is always more than the equivalent petrol version and the cost of the fuel in the UK has now separated, by upto 10p per litre, with no sign that this will change.
Just to be clear, diesel used to be cheaper but it now costs more than petrol by about 45p (nearly US $1!) per gallon.

Do modern diesel engines still need to be primed if they are run dry?: I understood that they can self prime from the starter motor.

A further question: Is all diesel fuel of the same quality, hence negating the problems experienced with petrol variability?
I'm not aiming to resurrect earlier threads about bio-fuels, additives and the like - just a question about the basic stuff served up at the fuel pump.

Thanks for all of the replies so far,

[Phil Flanagan]

Hi Dave

I run an iveco 4x4 1995 model with 2.5 turbo diesel.
A big decision in choosing this vehicle for our RTW journies was the fact that it has a simple, basic, no frills, no electronics engine. My theory being that any problems encountered could hopefully be easily rectified by myself or by any basic diesel mechanic.
Having been on the road over 2 years now and driven via Siberia and some fairly high altitudes I have experienced some issues :
Firstly, sparse populated countries with severe deep cold winters DO NOT (as i'd thought) run their trucks on diesel. For example Mongolia and that far east end of russia can have months of -40 (celcius) and so the diesel has the usual problems, therfore they run their trucks on a petrol/gas mix NOT diesel.
Second, Altitude, my engine looses performance once I get at say 2400metres, aything above this altitude makes a start in the morning (particularly on a -10 morning) somewhat tricky, though not impossible.

I camped in and around Santa Fe over christmas and every morning temperatures were at least -10 some mornings even down to -21 !
truck still started.
Other big advantage is eberspecher heaters run on diesel ! we heat our truck with same fuel as engine, this is a distinct advantage! and a great form of heating far better than gas.

My engine may not be the fastest most efficient machine but it keeps on going, it's easy to repair (though had no engine issues), it runs in wet conditions (like driving through rivers!), and dodgy fuel just means poor performance and not 'can't move'.
Usually, most countries have deisel cheaper than petrol.

In my opinion, if in a 4x4 and not planning a cruising tour of the interstates then always go for diesel. I'd certainly rebuy my truck again.

Phil.

[onlyMark]

"is all diesel fuel of the same quality?"
No.
Where you have octane ratings for petrol, you have cetane ratings (called cetane index or cetane number) for diesel.
That's how you end up with sometimes two pumps at the filling station, one for diesel and one for "premium" diesel.
Cetane numbers usually run from 40 to 55. After 55 there is no real extra gain in performance. High speed engines like a higher number.
The higher end diesel tends to have additives in the way of detergents and stuff put in depending on the country and local conditions.

Where I live the diesel is of poor quality and makes my car kick out more smoke than it would in Europe as the combustion process is less efficient and clean.
So, it isn't the same the world over in reality.

" Do modern diesel engines still need to be primed if they are run dry?"
It varies from vehicle to vehicle. It's not so wise to do it often though anyway. The reason is that the moving parts of the fuel system tend to rely on the diesel for lubrication. Hence when there isn't any, its not lubricated thus promoting wear. And diesel pumps aren't cheap and they're manufactured to very high tolerances, thus a small bit of contamination or lack of lubrication can be expensive in the long run.

Best not to let the tank fall below a quarter full in any case as you tend to get a build up of crap in the bottom over time and it's not good to get it picked up.

[silver G]

You also need to bear in mind that poor quality diesel is high in sulphur and as your engine oil gets older it has a very corrosive effect on the engine and seals - so needs to be changed more often. Modern high pressure diesel fuel pumps as in the TD5's wear very quickly without the correct additives too.

[Walkabout]

Originally Posted by Phil Flanagan

Firstly, sparse populated countries with severe deep cold winters DO NOT (as i'd thought) run their trucks on diesel. For example Mongolia and that far east end of russia can have months of -40 (celcius) and so the diesel has the usual problems, therfore they run their trucks on a petrol/gas mix NOT diesel.
Second, Altitude, my engine looses performance once I get at say 2400metres, aything above this altitude makes a start in the morning (particularly on a -10 morning) somewhat tricky, though not impossible.

Other big advantage is eberspecher heaters run on diesel ! we heat our truck with same fuel as engine, this is a distinct advantage! and a great form of heating far better than gas.


Phil.

The last few posts have drawn out a few downsides to diesel fuel.

I recall the "good old days" years ago, when the UK winters were generally colder, much colder, and diesel fuel used to cause problems in the fuel tank (turns more viscous I understand, possibly with a separation of the constituents?). Lighting a small(ish) fire under the fuel tank was the answer.

I am prompted to ask: does diesel fuel deteriorate in the tank, in a similar way to petrol, if left over time?

I had not thought about altitude: it's a well recorded issue for carburettored bikes, not so much for Fuel Injection bikes. I thought that all diesel engined vehicles are FI?

The point about heaters is similar to the concept of using a petrol cooking stove when travelling by bike (not concurrently of course!) thereby standardising on a single fuel.

An item on the UK news for today has been the introduction of bio-fuels at the pumps from tomorrow. I knew this to be on the way for diesel but apparently it applies to Petrol as well. Reported to be another EU-wide scheme with 2.5% bio initially, 5% from 2010 and aiming for 10% in the longer term.
However, the pundits reckon that this will do nothing favourable for the pump prices!!

[Walkabout]

Originally Posted by Phil Flanagan

Having been on the road over 2 years now and driven via Siberia and some fairly high altitudes I have experienced some issues :
Firstly, sparse populated countries with severe deep cold winters DO NOT (as i'd thought) run their trucks on diesel. For example Mongolia and that far east end of russia can have months of -40 (celcius) and so the diesel has the usual problems, therfore they run their trucks on a petrol/gas mix NOT diesel.
Second, Altitude, my engine looses performance once I get at say 2400metres, aything above this altitude makes a start in the morning (particularly on a -10 morning) somewhat tricky, though not impossible.


Phil.

Thanks for that information Phil.
Is diesel fuel readily available in these very cold regions where it is not used in the big engined trucks?
Anymore that you want to say about starting issues in cold or high altitude conditions would be of interest.

[quote=onlyMark;184181
" Do modern diesel engines still need to be primed if they are run dry?"
It varies from vehicle to vehicle. It's not so wise to do it often though anyway. The reason is that the moving parts of the fuel system tend to rely on the diesel for lubrication. Hence when there isn't any, its not lubricated thus promoting wear. And diesel pumps aren't cheap and they're manufactured to very high tolerances, thus a small bit of contamination or lack of lubrication can be expensive in the long run.

Best not to let the tank fall below a quarter full in any case as you tend to get a build up of crap in the bottom over time and it's not good to get it picked up.[/quote]

Mark, thanks also for the detailed replies: food for thought there. I can understand why it is not a good idea to run the fuel dry (not least, pulling crap into the system), but I did not think that the short time of running the fuel system without diesel, while priming, could have a major detrimental effect on the mechanicals.
A 1/4 tank "rule" seems to be very "conservative": in effect, you are limiting yourself to a much smaller tank range, one of the advantages of using the fuel.
Do you recommend flushing out the tank at intervals?


I am still interested in feedback on the questions here:-

Originally Posted by Walkabout

The last few posts have drawn out a few downsides to diesel fuel.

I recall the "good old days" years ago, when the UK winters were generally colder, much colder, and diesel fuel used to cause problems in the fuel tank (turns more viscous I understand, possibly with a separation of the constituents?). Lighting a small(ish) fire under the fuel tank was the answer.

I am prompted to ask: does diesel fuel deteriorate in the tank, in a similar way to petrol, if left over time?

I had not thought about altitude: it's a well recorded issue for carburettored bikes, not so much for Fuel Injection bikes. I thought that all diesel engined vehicles are FI?

One further question comes to mind:
It is well recorded that diesel engined road vehicles need regular changes of the timing belt (Ducati motorbikes ditto): this is another downside to the technology IMO because of the additional costs associated with the already expensive fuel here in the UK.
So, do petrol engined 4 wheelers have similar requirements for short-term(ish) servicing?


To my mind, the choice of fuelling for a 4 wheeled vehicle is still in the balance: I am not totally sure why this is so in my mind (I guess it is the wide range of factors), but further data about my questions here may help!

[onlyMark]

It is well recorded that diesel engined road vehicles need regular changes of the timing belt

My diesel Pajero has a chain so no need to change it. I'm not sure at all which diesel engined cars run on a belt. Can anyone clarify that?

but I did not think that the short time of running the fuel system without diesel, while priming, could have a major detrimental effect on the mechanicals.

It's the luck of the draw. Once probably wouldn't, but if a combination of factors come together, e.g. crap in the tank which has been drawn through when you ran out, filters need changing or poor quality foreign filters, cranking over for a long time possibly due to low temperatures and a cold engine etc. It's just not advisable (but I've done it at times).

A 1/4 tank "rule" seems to be very "conservative"

Is the "rule" not the same for a petrol engine as well? If so, then it makes no real difference, surely.
If you have a diesel doing 40 miles to the gallon and a petrol doing 30 to the gallon, both with the same sized tanks, both being filled at the the 1/4 full mark - then you still benefit. Or is my logic faulty?

Do you recommend flushing out the tank at intervals?

Only ever done it on trucks, never bothered with my cars, too difficult to get off.