When to replace motor?

Yes a motor will last for a long time. I'd just keep running the same type of oil you have always been using.

 

Anything is possible hand however the engine would likely succumb to obseletion or metal fatigue. Finding parts for a 1674 or a 1693, a 903 Cummins and even a 2 stroke Yamaha ( Detroit ) is difficult at best and when you do find them they have been abused.....

Yes it's possible....question is would you want the headaches of keeping it in service....

 

There is really no difference in keeping an old engine in service versus a new one.

 

Your going to worry yourself to death. Do your maintenance like clockwork. Drive like a professional. You have gotten more than your moneys worth out of it. No one can tell what is going to happen. Tomorrow or ten yrs from now it will lay down. I am a synthetic fan since the late 80s. But all oils are good quality now day. I would just have a plan and funds ready for the day it decides to a long nap. I'd be smiling and bragging my arse off about a good motor like that.

 

To answer THAT question is going to take some serious engine tests.

Cylinder balance test, cylinder leak test, compression test etc.

If THOSE numbers come out good, run it.

If there is any issues with them. Time to start planning a major in-frame or something in time.

It's called magnaflux and x-ray imaging of the engine.


My blog post on why I am buying a $6000 truck.
http://www.thetruckersreport.com/truckingindustryforum/blog.php?b=5184

 

moved to consolidate posts.

 

Really? And to think, all this time I thought only my old engine had leaks....but the new ones do it to huh?

You know what Les? You might have hit on something here.....go with it.....

 

I have and its worked out well. Funny how some people think cause its newer it don't break.....

 

You can run your engine infinitely if you'd like to, many do. Most people eventually give in to the rhetoric of too many miles or too obsolete but what really makes people upgrade is the fact that they've been driving this thing forever and they'd welcome a change and they're looking for a legitimate excuse to justify that change.

Synthetic oils are synthetic/mineral oil blends to maximize performance at a reasonable price. If you have excessive contaminants entering the crankcase oil without being filtered out you're better off with standard oil and standard drain intervals than high dollar syn blend and extended drain intervals.