I aslways get asked this question and dont know the answer. Can u switch back to regualr oil if the synthetic was in the car only for like 15 miles at most. Will any damage be done?

Yes you can switch. You can even combine the two.

In fact, they make a synthetic blend, which, if I'm not mistaken is a blend of synthetic and dino oil.

Yup, some are blends and some are 100%.

I honestly don't understand why people have this question. I've been using synthetics since 1983, and it was the same answer back then. Only thing I can figure is those who make fistfuls of money on petroleum oil don't want people to use synthetic, so they plant these little misinformation tidbits in peoples' minds.

The only problem with switching from synthetic to petroleum based oil is you're using petroleum based oil.

And what does this have to do with engine swaps?