I've always noticed my car runs nicer the hotter the weather is and the longer I've been driving. I installed an oil temp sensor with digital gauge yesterday. The oil temp takes far longer to equal the water temp but when it does, it exceeds water temp. Highest I had was about 83C after 10kms (20 mins) of driving in mild climate (25C outside).
My work commute is around 20kms in 20-35 minutes depending on time of day (drive home always takes longer because soccer mums).
My car specs 30 weight but I'm thinking about heading towards a thin 30 weight. Thinnest I've run was formula shell 5W30 several years ago (car ran fine). That was around 10cSt at 100C.
If my oil cooler (stock) is doing a good enough job to keep oil temps below 100C in summer weather, I'd wonder if a 20 weight would be fine in winter? Most people are against it as it's specced for 30 weight only. However, I have seen one UOA with the same engine here which compared a bunch of 30 weights and also a 20 weight. The 20 weight had slightly higher wear metals but it was honestly still quite low.
Now my actual question is along the lines of: Is a 20 weight at low temps actually thicker than a 30 weight at high temps. Is a 20 weight at 80C still thicker than a 30 weight at 100C? Does that mean no harm would be done so long as the temps remain low? Or is the "film strength" of the 30 weight still stronger even when it is at far higher temps than the 20 weight?
A viscosity calculator I downloaded (someone here made it I think) says that the 20 weight oil I've entered would be 12cSt @ 85C. The 30 weight I'd use would be 11.8 @ 100C. Basically the same depending on oil temp.
My work commute is around 20kms in 20-35 minutes depending on time of day (drive home always takes longer because soccer mums).
My car specs 30 weight but I'm thinking about heading towards a thin 30 weight. Thinnest I've run was formula shell 5W30 several years ago (car ran fine). That was around 10cSt at 100C.
If my oil cooler (stock) is doing a good enough job to keep oil temps below 100C in summer weather, I'd wonder if a 20 weight would be fine in winter? Most people are against it as it's specced for 30 weight only. However, I have seen one UOA with the same engine here which compared a bunch of 30 weights and also a 20 weight. The 20 weight had slightly higher wear metals but it was honestly still quite low.
Now my actual question is along the lines of: Is a 20 weight at low temps actually thicker than a 30 weight at high temps. Is a 20 weight at 80C still thicker than a 30 weight at 100C? Does that mean no harm would be done so long as the temps remain low? Or is the "film strength" of the 30 weight still stronger even when it is at far higher temps than the 20 weight?
A viscosity calculator I downloaded (someone here made it I think) says that the 20 weight oil I've entered would be 12cSt @ 85C. The 30 weight I'd use would be 11.8 @ 100C. Basically the same depending on oil temp.