Its Not About Synthetic And Non-Synthetic....That COmes Later
With Synthetic I Actually Mean That VISCOSITY With That.....Usually Syntheic Oils Are Pretty Much Low On Viscosity.....
Its ABout The Viscosity..... I Don't Think Someone Like A Watery OIL Running Across Chamber In Blasting HOT Humid Climate.....!
The Viscosity Matters Alot....Even If You Check The Owner Manual.....The Viscosity To Be Used Was Given As Per Temp.....!
New Cars Won't Bother It Much As Everything Is New And Have A Pretty Good Life Spam On Back.... Once The Aging Starts ..Here You Need To Check And You Think Using Same Viscosity Oil In Hot Summers.....! Its Not A Wise Idea........Sometime Later You Will End Up With Either Burning Oil Syndrome Or With Seals Seapage.....!
That's WHy Its Was Usually Told Not To Use Those Low Viscosity Oils In Older Cars.......!