Posted: Jun 05 2011 at 1:28pm | IP Logged

I just use the 7000-7500 mile range as something that makes me comfortable.  When my chain tensioners were replaed, the front of my engine was CLEAN inside.  No sludge or varnish or even discoloration.  You can go further and if so, I would use Mobil 1 EP that can go 15,000 miles.

Usually if you get a leak on an older engine when going to syn, it means the seals were full of crud and the syn cleaned it out and leaked.  If you run a new engine, syn is a great way to go.

As to UOAs..(used oil analyses).  They cost as much as an oil change and don't tell you much unless you have a coolant leak or a bad air filter.  You might as well do an oil change on a good engine as spend money on an oil analysis.