Can you mix synth with convec oil?

[Smokey Eddy]

I'm running convectional for break in and i want to top it up just a bit, can i add either clean or very lightly used synthetic?

I seem to recall they wont mix but that may be a myth.
there is semi-synthetic oils so im assuming they do.

[rabbitman]

I don't think it's a good idea to use synth on break in, it'll lube the rings so good that they'll glaze over rather than seat.

[cyrus #1]

I don't think it's a good idea to use synth on break in, it'll lube the rings so good that they'll glaze over rather than seat.

x2 on this.  You can mix the two with no problems though.

[Smokey Eddy]

oh yes i know. Pretty sure the break in is over now. 2 tanks of D later... or should i hold out even longer?

[macka]

the big myth here is the rings seating. If they didn't seat right away your engine wouldn't run, and you'd get a hell of a mess in your oil pan. We also hone the walls to promote the seal. It takes a long time to get the hone pattern out of the cylinder walls, and by then you'll know if you did the job right or you have to do it over again.