Synthetic is still natural oil. Synthetic stands for synthesized. There are 300 different size oil molecules. The little ones burn off the larger ones help sludge build up. Synthesizing oil means the best ones are removed that's what makes it more expensive and better oil. Mixing oil brands of...
Synthetic without a doubt. I was a tech for Toyota for nearly 20 years. The early 90's Celica GT-GTS would burn oil if they were driven aggressively. I had a new 92 and used Mobil 1 and went from 1qt in 1100 miles to zero between oil changes.