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

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,

__________________
Dave

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.

"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.

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.

__________________
Chris
-----------------
"Never have a stupid argument with an idiot - he gets a lot more practice than you"
there I go again
not too hard really

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!!

__________________
Dave

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:-

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!

__________________
Dave

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?

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).

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?

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

With regard to diesel deteriorating over time then yes, as Roger says algae can be a problem as can the accumulation of asphaltenes as the diesel breaks down - this is a black/brown sludge which quickly blocks filters, and will accumulate in tanks over time. It will not wear out pumps but it will cause problems...

Timing belts: well the Landrover Tdi300 engine was quite renowned for snapping in early versions and causing obviously major problems! Toyota allegedly not but I have seen at least one case of an (admitedly) abused 1HZ giving out while still within service interval (which is 150,000 kms on a 105 cruiser IIRC). Most Nissans I have used (TD42 Patrols and 3.2 litre D22 p/ups) seem to have nicely stuck with chains... Which landrover went back to for the TD5 but I have no idea what their new engine is!

My only other contribution is that CAT offer an ether injection system for starting big diesels in cold climates!
hope it helps a little bit,
Gil

Quote:
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?

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?



The good old days of having diesel fuel wax up in most climates have gone with the advent of winter mix fuels, some high tech additives like kerosene usually drop the cloud point of diesel enough for anything except seriously long periods of minus 15C and below. Most truck manufacturers selling into known cold markets will include "Arctic/Alaska/Siberia kits" of fuel tank heaters and insulated and 24V traced fuel delivery lines as well.

Diesel will deteriorate over time, but usually its an algae that grows in the tank, an additive will stop that. Its more likely that condensation inside the tank will cause problems over time. The fuel will float on the water, the pump will pick up water and the owner claims bad fuel, always a good idea to have a water separator before the fuel filters which can be drained off. Most diesels have some sort of manual lift pump, so its a good idea to use that if the vehicle has been sitting for a long time, you can get the water into the separtor, drain off, then fire up the engine. Once the water is in the filters and pump its time to start replacing bits.

With altitude problems, its a fine line between the reduction in oxygen and reduced temperatures which then reduces the burn of the diesel fuel - the same problem occurs on petrol engines as well but its not as critical as there is a spark plug to cause ignition. Whereas diesel requires the compression and heating of the air charge then the injection of the fuel into the hot air to cause the burn. My memory fails me a bit, but I think the optimum temperature to oxygen density of the air charge is 38C, hence the need for cooling the air charge down with intercoolers and aftercoolers on turbo engines. There are so many brands of "cold start" aerosols on the market its not funny, all have an ether and butane base, couple of squirts into the air cleaner and any diesel will start as long as there is fuel.

Modern electronic diesels also have oxygen and temperature sensors which can accomodate altitude (low oxygen) and temperature differences by retarding or reducing fuel injection times. Overfueling a low oxygen air charge will not let the fuel burn as the mix will be "too rich" in old terms. But when the circuit board dies in the middle of Whoop Whoop unless there is a "limp home" mode you are stuck.

I've not heard specifically of timing belt problems for small car diesels, in commercial based vehicles it would be a brave engineer who specified changing timing belts/chains at less than 500,000kms on a light truck, and up around the million kms on a heavy truck.

Servicing of diesels based on Kms is really a hangover from the pre electronic days, the engine and driveline should be serviced based on engine revolutions which is an indication of the work done. Best aftermarket purchase you can make is a total engine revolution counter. I've seen metropolitan delivery trucks rack up the same amount of engine revolutions with stop start driving in 8 weeks as a highway truck does in 14 weeks.

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