Buys semi-synthetic oil to put in CLEAN when he does his filter change. Note: CLEAN. Not mixing with anything that is in it right now.
Returns it because he doesn’t want to mix conventional and synthetic because he thinks his car will blow up.
Meanwhile, he previously bought semi-synthetic, A MIX OF CONVENTIONAL AND SYNTHETIC.
Clearly oil companies are selling semi-synthetics because they will blow up your car.
There is a purpose for this. Because semi-synthetics help your car run cleaner and better.