Why do Diesels supposedly last longer than petrol engines ?

[MarkVS]

Being the mechanic novice that I am, I was looking up the basics on how diesel engines work as opposed to petrol.

One of the things that I couldn't quite work out, is why there is so much talk about diesel engines lasting so much longer than petrol.

Why do they ? what is do different ?

Is it something as simple as the fact that diesel engines are unlikely to do as many 'rev's over their life....or being a slightly simpler motor, less that can go wrong....or..they would have better heat dissipation so they don't run as hot so last longer ?

Any mechanics that fill the understanding gap..


Mark

[chester ver2.0]

Stronger block and internals to handle the compression

Less moving parts asa it relies on compression to go so there is no ignition system to speak (apart from glow plugs to start it)


However this is old school diesels modern CRD is now as complex as petrol with the same lifespan

[MarkVS]

Stronger block and internals to handle the compression

Less moving parts asa it relies on compression to go so there is no ignition system to speak (apart from glow plugs to start it)


However this is old school diesels modern CRD is now as complex as petrol with the same lifespan

Thanks for that..so it is as simple as I thought..simpler motor, bigger engine block etc = longer life.

Thought I might be missing something.

Thanks

Mark

[tk421]

only if they're looked after

they get most power at lower rpm = less revolutions over its lifespan = less wear and tear

[KingBilly]

Traditionally diesels were plonkers with low revs and lots of torque.  They would just idle along doing the heavy work or pulling large loads.  They mostly had a wide torque curve, as opposed to peaking at high revs like their petrol equivilants.

But now, not so much.  Many diesels are turbo charged, some with two turbos.  Think with modern diesels, a lot of the old longevity arguement has gone out the window.

KB

[Footy Shorts Shane]

Traditionally diesels were plonkers with low revs and lots of torque.  They would just idle along doing the heavy work or pulling large loads.  They mostly had a wide torque curve, as opposed to peaking at high revs like their petrol equivilants.

But now, not so much.  Many diesels are turbo charged, some with two turbos.  Think with modern diesels, a lot of the old longevity arguement has gone out the window.

KB

 

I have been holding back from commenting on this topic, but KB has pretty much nailed it. 

(Had I commented, GG would have moved it to the Daily Rant thread, and most here would hate my guts, FOREVER !!  )

[KingBilly]

Had I commented, GG would have moved it to the Daily Rant thread, and most here would hate my guts, FOREVER !! 

Mate, I enjoy reading your posts/replies.  I learn something most times or get a laugh, sometimes both.  Don't ever be afraid to post your opinions, they mostly make sense 

KB

[DaveR]

  but KB has pretty much nailed it. 

The diesel lasting longer thinking comes from industrial and marine engines mostly, heavy vehicles to.
Cars with small diesels, different story.

Then to add confusion, high speed marine diesels last no where near as long as medium or low speed.

[GeoffA]

 

I have been holding back from commenting on this topic, but KB has pretty much nailed it. 

(Had I commented, GG would have moved it to the Daily Rant thread, and most here would hate my guts, FOREVER !!  )

He has indeed.

Now we'll just have to find some other reason Shane......

[loanrangie]

Petrol washes the oil off the cylinder walls promoting wear but diesels are only compressing air until diesel is injected on the ignition stroke, plus diesel is just thin oil so has better lubricating properties than petrol.

[Swannie]

Mate has a petrol 80 series still going strong with 550ks on it

Swannie

[dales133]

Diesel engines generaly have alot lower compression witch I guess has a bearing on longevity but a badly maintained diesel is destined to fail prematurely well before a badly maintained petrol.
My 80 series has done about 350k and still strong as an ox

[Mace]

^^^^

I think you mite be slightly wrong there. 

Diesels usually have compression ratios of 16:1 and greater.

http://auto.howstuffworks.com/diesel1.htm

[xcvator]

and most here would hate my guts, FOREVER !!  )

Ah don't let that stop you,coz we will anyway 

[GGV8Cruza]

 

I have been holding back from commenting on this topic, but KB has pretty much nailed it. 

(Had I commented, GG would have moved it to the Daily Rant thread, and most here would hate my guts, FOREVER !!  )

Dont pick on me just because I drive one of those twin turbo jobbies, I had no choice in the matter, it made me do it 

The dark side has it's ways

GG

[Footy Shorts Shane]

They truely would be a good thing, if they had spark plugs, an ignition system and ran on petrol 

#tractorengines 

[tk421]

The diesel lasting longer thinking comes from industrial and marine engines mostly, heavy vehicles to.
Cars with small diesels, different story.

Then to add confusion, high speed marine diesels last no where near as long as medium or low speed.

There's a boat that's powered by two Prado D4D engines. And we all know that stands for D4Detonation.

(Yes I drive a D4D)

http://m.drive.com.au/motor-news/its-a-toyboata-20141015-116fgl.html

[fishfinder]

I reckon if you had both diesel and petrol of roughly the same capacity kept both serviced prior to service intervals and had working conditions the same, you will probably find the life span on both be pretty close the same.

[GeoffA]

#tractorengines 

Yep. Ideal when travelling and towing further than around the block.......

[Bird]

They truely would be a good thing, if they had spark plugs, an ignition system and ran on petrol 

#tractorengines 

TD42 started as a Forklift engine

[Footy Shorts Shane]

TD42 started as a Forklift engine

And that's where they should have stayed  (Never have seen one in a forklift, heaps of 25/27's though)

The TD42 wouldn't be a bad thing, if it was direct injection, didn't split bores, didn't blow head gaskets, didn't cavitate the timing cover away, or the water pump, didn't crack heads, didn't pull head bolts and ran on petrol 

[gordo350]

And that's where they should have stayed  (Never have seen one in a forklift, heaps of 25/27's though)

The TD42 wouldn't be a bad thing, if it was direct injection, didn't split bores, didn't blow head gaskets, didn't cavitate the timing cover away, or the water pump, didn't crack heads, didn't pull head bolts and ran on petrol 

Isn't that a 186 red motor?

[Bird]

ambivalent

[Nifty1]

Well I reckon it's more to do with what they are used for. Until recently, diesels were most often found running trucks, tractors, generators, locomotives or boats. They would usually run around the maximum torque point, run for days or months without stopping, maintain constant revs and temperature, and not get thrashed. Petrol engines often had a very different life with frequent stops and starts, cooling down at night, and revving hard right through the range when in use. Perhaps if they were operated in the same way as a diesel they might last almost as long.But I know next to nothing about engines.

[Symon]

Old school diesels were usually long stroke, low revving engines that spent most of their life at less than 3000rpm.

New common rail diesels are shorter stroke, and higher revving.  Essentially they are made now to match the performance of petrol engines.  They are also more complex now with fuel systems running at very high pressures and more things that break.  There isn't much difference in the expected life of the two types of engines these days.