Re: New Vehicle Oil Change?

Ray O wrote:
"Joe" <really-faked-but-works@xxxxxxxx> wrote in message news:Ou30k.41$pK.36@xxxxxxxxxxx
IMO, you should ignore all future advice from whoever told you to change the oil in the first 50 miles because the source of their advice is suspect.

Follow the maintenance schedule in your owner's manual for best and cost-effective results. Changing the oil too early can interfere with engine break-in.
I hear this all the time and as a machinist-of-sorts working with tolerances at a higher level than Toyota, I wonder why or how this might be true...

What would or could it interfere with? All I can think of is that maybe the first batch of oil with the micro-residue from break-in sets the seals in a certain way or maybe makes sure the rings are running on a surface in a manner that "seats" them better.. To much proper lubrication can cause too little break in when it is desired, but I would think an early oil change would simply delay the break-in and remove possible large contaminants that would possibly cause undesirable side effects.

Your thoughts are on the right track. Changing the oil early can delay break-in and prevent proper piston ring-to-bore fit.

Since you are familiar with machining, you know that modern machine tools can achieve a cylinder bore finish that used to be possible only by grinding with a jig borer - almost mirror-like, yet automakers purposely leave a fine cross-hatch finish on the cylinder walls.

What is jig borer. I looked on wikipedia, but didn't get a good explanation. When I worked for my father, who used to rebuild engines, I bored quite a few cylinder blocks and honed the cylinders to get a cross-hatch. However, the boring equipment was completely different that what they use in the factories.

> The ridges on the cross-hatch and
very fine particles suspended in the motor oil help the piston rings seat properly, and after the cross-hatch has worn off, piston ring seating slows down greatly.

How, exactly? I would think that the cross hatches cause the piston rings to rotate slightly as the pistons go up and down. I would imagine this helps them get seated properly. I understand your explanation below, but what exactly seat properly mean? I would think it means that the rings are fully expanded against the cylinder walls, so that there is not a gap that the gases (both exhaust and unburned gases during the compression stroke). Is this correct?

If the rings do not seat properly, you get more blow-by, reduced power, and greater oil consumption

Conventional wisdom used to call for a very early oil change to remove metal particles large enough to damage the engine, but modern oil filters trap that stuff so very early oil changes are no longer necessary or even desireble.



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