I have heard someone tell me (after I'd already started using it...talk about wishing I'd had hindsight!!!) that running 100% synthetic oil in a new Jeep engine (I'm running a rebuilt 258 I-6) will keep the "rings from seating right" and end up causing me problems down the road...
Is there any truth to that? I'm reading The Jeep Bible, and those guys seem to think it's hogwash, and I'm loving that book, but....what's the general consensus? Anyone have problems?
Rings 'Seat' in the first hour or two of operation.
I don't use synthetic for 'Break In' period, which is usually the first hour or two...
I change oil after the first half hour to hour after first start.
That is where you will get the vast majority of metal from starting up new parts and then 'Clearanceing' themselves.
I usually put new oil/filter on, and then go about 500 miles,
After that, it's time for new filter/oil of what you are going to run for the next 3,000 miles or so.
We had race car engines that were 'Smoking' after doing several races, so we tore them down to see what the 'Problem' was...
No problme, rings hadn't seated yet and oil was still getting past them into the combustion chamber!
One hour with regular oil, then right back to synthetic solved the 'Issue'...
Camshaft/lifters/pushrods/rockers all seat in the first 20 minutes,
Rings will take one to two hours to seat with regular oil.
Pistons NEVER seat in the cylinders, so that is hogwash,
But the rings DO need to mate with the cylinder walls, and that takes some friction that synthetic oils don't let happen.
Synthetic oils have MUCH smaller molecules, so if you plan to run synthetics, use a MUCH finer hone on the cylinder walls, use torque plates during honing to keep the cylinders round,
And heat the block while honing to keep the cylinder from doing stupid things when it warms up...
I also like using stainless steel oil control (wiper) rings with synthetics because they just do a better job keeping the synthetics in the crank case and out of the combustion chambers...
If your engine was 'Broke in' before you started using synthetic oil, then you have NO ISSUES if you don't see oil smoke or find lots of carbon on the backs of the exhaust valves.
If you are getting ready to start a fresh engine,
Or you are building an engine for synthetics,
Smoother cylinder walls,
Cylinders that are ROUND & STRAIGHT when hot with the head torqued in place and stainless oil control rings are a good idea,
But break that engine in with common oils first, then run the synthetics.
I've heard this as 'Theory' so I can't tell you for sure one way or the other...
Breaking a camshaft in with regular oil is a good idea.
Most people in the know seem to think the larger molecules of regular oil help keep the lifter up off the camshaft lobes during the break in process.
The line of thinking is,
The smaller molecules of synthetics allow the 'Defects' in the cam/lifter surfaces, burrs, ect. to dig in, where larger oil molecules will allow the surfaces to clearance each other without as much damage.
But like I said,
In 20 minutes of running, the cam either breaks in correctly, or wipes it's self out, and that is when I'm using regular oil anyway, so the 'Issue' is moot for me...
Just letting you know what I know and have heard,
I can't tell you if the 'Theory' is correct or not,
I just know I have a lot less 'Issues' when we break in with regular oil then switch to synthetics.