After years of coming across this topic of dino for break-in and syn therafter I have come to the conclusion that running dino first rather than syn is not necessary. I agree with the comment above if this were true porsche and mercedes etc. (who run mobil 1 from the factory) wouldn't do so if this idea were true.

In all honesty from all the oil lab tests I have read posted here and on other forums, synth is obvously superior but not so much in the wear department. Yes it has more detergents and lasts much longer than dino oil and for these reasons it better prevents wear, but not because it is somehow more lubricating, but simply because it holds its lubricating properties longer. All things being equal both oils lubricate equally up to about 3-4000 miles at which time dino oil begins to degrade at a faster rate than synth.

Using this as my underlying opinion, I hold the that the dino first then syn after break-in doctrine is not necessary, start with whatever you want. Personally, I started with the factory dino oil in the car when I bought it new and changed to synth at ~600 miles. Use what you like, just change it regularly as recommended by a lab test or simply common sense.

 

at the college my buddy went to they had a guy from castrol visit the school and he asked him about the very same thing and he said it does not hurt the engine even if you from syn to regular oil but dont hold me to that i did not hear it from the castrol man but my bud is pretty trust worthy hope this helps

 

I believe that it used to be true that switching back to conventional from synthetic was bad. But I believe that recently (within the last 10 years) under federal law, all motor oils under the same specs can be mixed with any others with no adverse affects to the vehicle. Imagine how things can be if they didn't make that a law...