Quote:
Originally Posted by 99AUXR
Mineral oils get thicker with age e.g a 5w30 will head towards an SAE 30. Synthetic oils however dont thin and hold their viscosity. However the additive packages are depleted if the oil could be cleaned and additive pack restored you theoretically would never need to change the synthetic oil.
As for cold starts yes they will be effected by the warm weight of an oil because for example at 30 deg c a 5w-40 oil is thicker than the 5w-30 oil.
You cant really compare the winter rating of the oil across different hot viscosity. E.g 0w40 vs 5w40 vs 10w40 vs 15w40 and then to compare 0w30 vs 5w30 vs 10w30 etc.
As for your issue its not really an oil thickness more so oil draining away from places it needs to be. The 5w30 still offers better startup protection and ample hot protection for that engine especially when it is not seeing a race track where high oil temps become prevalent, on the road oil temp usually follows coolant temp.
This is pasted from the S/C 5.0 Thread - Note the winter rating doesnt mean the oil is same viscosity when cold as its affecting by the viscosity at 100 deg C.
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Great post 99AUXR!!! Definitely makes sense to me & clears things up, though because of the mileage on the motor (216,xxx) I will try the 5/40 next & see how it goes, if the syn power don't work out, a semi synth is on the cards next but not a too fast flowing one hey!
cheer's, Maka