[ScoTFrenzel]

Originally Posted by bluesman2333

That makes no sense to me. Are you saying all new engines from the auto plants use break in oil that ruins cats or don't use break in oil and do fine anyway? The other option is they use break in oil that doesn't ruin the cat while protecting the engine for the first 2000 or so miles.

The last 30+ years new cars have NOT used break-in oil off the assembly line but just the standard 10w30 etc...... now 5w20 etc.
Rings and cylinder wall honing techniques are such that the old traditional thoughts about "break-in" are antique procedures used back in "the good old days".

Some late model vehicles are built with techniques that allow factory installation of fully synthetic oils at initial start up, with no actual break-in necessary beyond "taking it easy for the first 500 miles".

[y112]

Regarding the reply stating that automakers haven't used break-in oil... I never said that they did. Please re-read my reply and you see that I mentioned that the zinc content has been removed to prevent catalytic converter damage, and as correctly mentioned by another contributor, these newer motors have roller cams.

Regarding breaking in engines with synthetic oil. Most of the inquiries on this forum pertain to local machine shops and new "do-it-yourself" people, some of which may not have hot water controlled stress plates and automatic cylinder
hones. It's funny that the cam manufacturers, Precision Engine Machinist magazine, Engine Builder magazine and Automotive Engine Rebuilder Association hasn't recommended starting new engines on Synthetic oil.

Besides, who in their right mind would start up a new rebuild with $6 to $8 a qt for synthetic when 30w oil is cheaper, considering that the normal Break-in procedure involves bringing the engine to operating temperature, and changing the oil to remove any debris or break-in lube (for flat tappet cams). None of my customers care to spend $ 48 to $64 for oil that is only going to be run for 30 minutes max.