Why Do Diesel's Last Longer Than Gas Engines?

jelly

Well-known member
Joined
May 28, 2004
Location
Kentucky
Why Do Diesel\'s Last Longer Than Gas Engines?

Lower rev's?
They're built stronger, but also put more stress on the parts...

So what's the secret?
 

dieseldorf

Top Post Dawg
Joined
Oct 11, 2000
Location
MA
TDI
ex- 1996 wagon, ex-2000 Jetta
Why Do Diesel\'s Last Longer Than Gas Engines?

much more robust and much closer tolerances than a gasser....they are designed to be driven!


 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
Why Do Diesel\'s Last Longer Than Gas Engines?

More Mature drivers who know to take care of their cars ?
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
Why Do Diesel\'s Last Longer Than Gas Engines?

Better ring sealing, longer piston skirts, heavier blocks, stronger conrods with stronger big-end bearings, stronger main bearings and long-life valve seats helps a lot...

Oh, also CI-rated oils are designed to meet higher specs and help prolong life of parts.

Cooler cylinder wall temperatures than gassers (from having excess air...running in ultra-lean regimes at light loading/partial throttle which means 90% of the time.)

Lowered RPM's extends life of all reciprocating and bearing surfaces.
 

Muggins

Veteran Member
Joined
Jun 7, 2002
Location
Barrie, Canada
TDI
02 Golf GL 4dr 5spd
Why Do Diesel\'s Last Longer Than Gas Engines?

yeah, the engine block is bullet proof, it's all the peripherals that break prematurely, from turbos to brake master cylinders, glow plugs, harness, timing belt, clogged intakes,etc.


Kind of ironic, eh?
 

mailman

Veteran Member
Joined
Oct 30, 2002
Location
USA - CT
TDI
99.5 Black Jetta TDI
Why Do Diesel\'s Last Longer Than Gas Engines?

Ahhh, glad you asked!

Look at the gas engine's primary weakness ... it has to run at stoichiometry (i.e., fixed air/fuel ratio). It requires a fuel with a fair amount of octane (i.e., gasoline). As an engine wears, the piston rings become worn and oil begins to work its way into the combustion chamber. This oil significantly lowers the octane of the fuel mixture and we get reduced power output at best and engine knocking at the worst. So, we have to work the engine harder, wears more, etc. ... it's all downhill after that. Not to mention the engine beating itself to pieces if it is knocking.

Now, the sweet diesel. Sure, the rings still wear. But the beauty of compression ignition is that we don't want high octane. We want high cetane and, ahhhh, the beautiful diffusion flame it supports. Now, oil leaking past the rings in a diesel engine is the equivalent of adding more fuel for the engine to burn. One might argue that the diesel actually runs better when worn ... hmmmm.

That's my 2 cents!


P.S. We can also consider the fact that gas engines cook themselves up at idle, while our diesels run nice and cool. Ahhh, the beautiful diesel.
 

Kabin

Veteran Member
Joined
Sep 8, 2004
Location
Valley of the sun
TDI
Jetta '04 PD TDI/Tip
Why Do Diesel\'s Last Longer Than Gas Engines?

Not sure about the TDI, but most diesels wash the cylinder walls at idle, which is a negative. Of course one can add a fast idle to fix that.
 

Bob_Fout

Oil Wanker
Joined
Sep 5, 2004
Location
Indiana
TDI
2003 Jetta - Alaska Green (sold) / 2015 GTI 2.0T
Why Do Diesel\'s Last Longer Than Gas Engines?

Not sure about the TDI, but most diesels wash the cylinder walls at idle, which is a negative. Of course one can add a fast idle to fix that.
What does that mean?
 

nicklockard

Torque Dorque
Joined
Aug 15, 2004
Location
Arizona
TDI
SOLD 2010 Touareg Tdi w/factory Tow PCKG
Why Do Diesel\'s Last Longer Than Gas Engines?

The wash effect you talk about explained for others: 'wash' is when an engine is running in a rich fuel/air mixture regime, some of the fuel sprays on the cylinder walls and dissolves the light film of oil away, exposing it to wear (from metal to metal contact by piston rings) and the combustion flame front.

Someone correct me if I'm wrong, but it's my understanding that in a CDI engine, there simply is no regime which can remotely be considered 'rich.' For the most part, CDI engines (direct injection) run in the lean to ULTRA lean regime, especially at idle (ultra lean), so there is never any diesel not being burned and ending up washing your cylinder oil coating away. Also because of the careful 'swirl' design of the combustion chambers, the flame front is 'cushioned' by an outer wall of cool air, protecting the cylinder walls (and piston crown) from direct flame front exposure most of the time.

IDI engines did this at cold start and under other conditions a little, but diesels have always had less of a problem with wash compared to their gas counterparts (variable fuel mixture ratio of diesel)
 
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