Yep

 

My rx8 was reaching consistent temperatures up to 210F... I ended up buying an all aluminum radiator thinking it was the old radiators fault but temps remained the same. I then purchased a relay fan kit from rotaryperformance that activates both fans at full speed at around 180F. Now my problem is that temps might be a little to low :/ my temp gauges when cruising read around (178-185)F coolant & (165-180)F for oil temps.

 

Yes ... temps that are too low can be bad ..... hard to know where the cutoff line is ...but I reckon the guys at Mazda probably had more idea on this than anyone here .....

 

The thermostat controls how low coolant temperature can go. So that coolant temp sounds fine.
Oil temp is in the right ballpark for cruising, but either way, there is nothing (advisable) you can do to change it.

 

Sounds like he has a system where the fan is constantly battling against the thermostat for temp control . Fan control should be around 200F minimum . Maybe not a bad thing for oil/water temps on stock thermostats but ...... something has to power those fans. It's just wasting petrol while wearing out the fans and alternator................. IMO

 

Lets also cover something that hasnt yet been said....
If I understand and follow correctly, you Kamal said you hadnt changed your thermostat. You JUST had your motor rebuilt. You shouldve replaced that thermostat when you went did the rebuild, especially since an older worn thermostat can stick and cause issues regulating engine temperature. Stop driving the car and replace the thermostat NOW. All the cooling mods in the world wont save your motor if your thermostat isnt operating properly and doesnt allow coolant to reach the radiator.

I think all of us can agree on that. Let us know what you find after you replace that.

 

I'm due for an oil change soon , I'm thinking running 5w-30 instead of the 0w-40 that it has now.. maybe the thinner oil will help raise some oil Temps. My coolant temps are fine I think! Thanks.

 

Actually, thicker oil can maintain higher oil temp.

 

Try a relay fan kit from rotaryperformance.com or rx8performance. My coolant temps where around 210F but they don't go past 180F when idling now even on a hot summer day.