Is full synthetic motor oil worth the extra cost over conventional or blends?

For modern engines, the consensus across the mechanics and oil-analysis communities we read is yes — most newer vehicles specifically require synthetic, and even where it's optional, the cleaner additive packages and better cold-flow protection typically justify the cost. A frequent caveat on r/MechanicAdvice is that 'oil is 95% marketing' once you're inside the name-brand synthetic tier, so the bigger ROI is changing on time rather than chasing premium SKUs.