Can a straight 40 weight oil be mixed with a straight weight 40 synthetic oil?.

NO STRAIGHT OIL SHOLD BE MIXED WITH ANY SYNTHETIC OIL !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Should they be mixed, not necessarily, unless needed.

Can they be mixed, the simple answer is yes. However, do to mixing them, you will not get the benefits of having only synthetic. By federal law, all oils have to be able to be mixed, with the exception of some greases and compressor oils, because some can differ in basestocks that wont mix together.

Who makes a straight SAE 40 wt synthetic?

Nobody I know of...all synthetics I believe are multi-vis by nature anyways.

So you would be asking if you could mix something like Amsoil Marine Synthetic 15W-40 with conventional 40wt?

You probably could ...what you would wind up with is ??

You would have to run a bunch of tests to see what your blend has to offer...


Stick with M-1 V-Twin 20W-50