Appropriate mileage to begin using synthetic oil?

[Patman]

Technically speaking why would a diesel engine take longer to break in? Forgive my ignorance on the subject but aren't diesels pretty much the same as gas engines (mechanically speaking) other than just glow plugs and the higher compression ratio? What else about them would need the longer break in?

 

[OneQuartLow]

I understand it has to do with materials and the fuel. Tougher piston/ring alloys (diesels are made to work) and better fuel lubrication means ring seating takes longer. 10Kmiles is supposed to be common.

This from freight company owners in my extended family. I've never owned a diesel.

David

 

[dragboat]

quote:

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Originally posted by Patman:
Technically speaking why would a diesel engine take longer to break in? Forgive my ignorance on the subject but aren't diesels pretty much the same as gas engines (mechanically speaking) other than just glow plugs and the higher compression ratio? What else about them would need the longer break in?

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Chrome Rings take longer to seat in. In the past I have seen some tht never did

 

[G-MAN]

quote:

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Originally posted by Patman:
Technically speaking why would a diesel engine take longer to break in? Forgive my ignorance on the subject but aren't diesels pretty much the same as gas engines (mechanically speaking) other than just glow plugs and the higher compression ratio? What else about them would need the longer break in?

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Patman, there's a whole lot more different about diesel and gas engines than that.

A lot of diesel's (direct injection type) don't even have glow plugs because they don't need them. Their higher compression ratio generates enough heat to facilitate a cold start without the heat generated by a glow plug. As far as combustion, that's the only time a glow plug would come into play. A diesel is a compression ignition engine.

The higher compression and the fact that diesel combustion is literally an explosion rather than a slow burn (as in gasoline engines) means the pistons, rods, bearings, crank, and block all have to be quite a bit more robust than an equivalent gas powered engine. When GM was busy in the late 70's creating their car and light truck V8 diesel, they initially thought it would be just a matter of slapping some Recardo chamber heads on an Olds small block. The first prototype split the block wide open two minutes after it was first started. Back to the drawing board. In the end, the Olds small block was so heavily modified to stand the stress that it weighed more than the old Olds big block. Nevertheless, that engine still had reliability issues until it was finally discontinued.

 

[Patman]

Thanks for the explanation guys! As I mentioned, I'm pretty clueless when it comes to diesels.

Now I'm slightly less clueless.

 

[RogerUK]

My Nissan dealer told me it was ok to drain and refill with Mobil 1 0-40 as soon as I took delivery of the new car, The man at the Mobil Technical Helpdesk advised I should perhaps put on 1500 miles first. I compromised and changed oil and filter at 1000 miles, will change again at 3000 and then every 3000, all with Nissan filters and Mobil 1 0-40.
Great forum, my wife thinks I am mad!
Roger

 

[Ken2]

Roger,
Why drain at 3000 miles?...that oil should be good for much longer mileage.

Ken

 

[Ken2]

XHVI

Can I nitpick what you wrote about diesels?...

Many diesel engines without glowplugs either need heat on the waterjacket or prelubed oil to start, or they'll need starter fluid sprayed into the air (not good, but it gets the job done...one time I had to start a 2700hp ALCO in below freezing weather and the engine heat was inadvertently off...I sprayed two cans of ether at the same time, the engine rattled 'n banged, but it started).

Diesel fuel combustion is not accurately described as an explosion--the amount and duration of fuel injected is timed to avoid excess combustion pressure. I've pulled indicator cards on engines that show the pressure rise vs. the piston position, so we are sure that the timing is correct and pressure spikes are avoided. The engine is indeed stout, for the compression pressure, for the combustion pressure, and for long life.

Ken

 

[RogerUK]

Ken
I do mostly short runs of less than 10 miles and only one good run of about 60 miles in any one week so I prefer to err on the safe side and drain out every 3000.
Roger

 

[S76Drvr]

What about manufacturers that deliver with syn in it?