My first year Mazda3 has always had 5-20 and runs flawlessly. IMO flow in startup and on cold mornings is more important than high temps here in Rochester. The car is basically a very cheap piece of work, and the body will disintegrate long before the engine shows any significant wear. Reliability of things like wheel bearings and suspension parts has been poor, not to mention the poorly protected body parts, but the engine has been great.