Link to WalMart Oil Deals

I know not many have Fleet Farms or Farm and Fleets nearby, but every month or so they have very good deals on regular, semi synthetic, and full synthetic oils usually Citgo, Mobil, oils though.

I am thinking of switching it up to full synthetic in all my vehicles though. I ONLY use full synthetic in my newer tundra since calls for it 0w-20, the rest use regular oil 5w-30 or 5w-20. Reason is the price of full synthetic is going down and down to reasonable pricing and although higher priced, not that much more now for full synthetic vs. regular conventional oil NON synthetic.

Another oil thread but any drawbacks or dangers from switching any motor (car or cycle) from regular oil to full synthetic even with some cars at 150K miles all on regular oil all it's life? Some say once you switch to full synthetic you should never go back to regular NON synthetic oil? Is that true? One would think the engines would not mind as long as change oil as I do every 4500-5K miles. Owners manual calls for regular oil on all my vehicles (except truck) and oil change intervals of 3750 for SEVERE use and 7500 miles for regular driving. I split the difference to never over 5K miles since prior to covid I was putting on 5K miles in 4 months although with GDI engines the OIL gets near BLACK in a matter of 2-3 months after a fresh oil change. GDI engines run more efficiently, but due to their design, the engine runs dirtier much quicker and blackens the oil much much quicker than say my old pontiac vibe 1.8L engine that even after 4000 miles still looks fairly clean NOT black just darker colored oil is all.