Please advise me, Carlanders, I just got a new engine for my EOD, my mechanic removed the thermostat saying that it could cause overheating to my engine if not remove. The car ran without thermostat in my previous engine and with fan bypassed, yet the car was so overheating and makes a knocking sound when drive for more than 20minutes.

My question is should I removed the thermostat in this new engine or leave it.

And I equally want to know if Mobil 5w30 oil will be fine on the engine, thanks for advise.

I have always run my 2002 Toyota Camry with thermostart, a mechanic once remove it, I went to another and fix it back.

Yet with time another removes it again and to avoid unnecessary argument I also went to anothe and fix it back.

Removing car thermostart is wrong short cut to car heating problem used by most mechanics do to inexperience or laziness.
When a car started heating up, all effort should be made to discover to actual cause and correct it not disconnecting the all important thermostart.

In terms of oil, I always use 5w 30 full synthetic oil.

Thank you���