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1996 GMC 4.3 Liter

What is your recommended Engine Break In Oil ?
Amsoil, Joe Gibbs, Royal Purple, Lucas additive, STP Oil Treatment additive ??
Does the extra cost $ match the function / purpose of these ?

 

This may or may not help, but I just used Cheapo non synthetic 5w30 when breaking in the rebuilt engine in my 97 Jimmy.

Changed it at 50 miles, then 500, then normal intervals... Never had any issues.

Make sure you prime it with an oil pump primer, IMO that is more critical on a new engine than any special oil.

 

X2 to KM346! DO NOT use a synthetic lube to break in a new engine!!! And do not switch to a synthetic till the engine has broken in! I also agree with the initial change intervals,this will assure long engine life,I have followed this regimen even on vehicles I have bought new with excellent lifespans.The factory fill oil is junk,as was the initial run in oil on the factory bench.The sources I have seen determine this to be little better than hydraulic fluid and it is used for thousands of engines,thats why its bright green when you change it at 500 miles!