18-12-2017, 12:36 AM
From the graphs in book Which Oil, except at very cold temps multigrades are surprisingly thick. 20w50 at 0C is much thicker than 30. 20W60 would be worse.
Nevertheless decades ago when my car was everyday transport I spent a winter in Dunedin at south of South Island (although still a moderate latitude cf UK). The car lived on the street with regular frosts and started OK every morning using XL or thicker, although crank speed modest.
I suspect the relatively thick oils originally recommended predated anti wear additives. Thick oils were also largely to reduce noise and consumption.
Presumably there are readily available inexpensive thinner oils 15W40 etc with 1980s or later API ratings.
For a low annual mileage oil burning filterless Seven, expensive synthetics a bit like “feeding chocolate to pigs”. (An expression I picked up decades ago. A very senior govt engr got into deep poo for using it to describe the proposal to use CNG for electric power generation. Which NZ did anyway. For a period it was popular here for cars. I tediously adapted my 1950s model. But cars became too complex to adapt, the power loss was considerable with moderns, and the whole vast industry collapsed before I had saved the cost of the kit!)
Nevertheless decades ago when my car was everyday transport I spent a winter in Dunedin at south of South Island (although still a moderate latitude cf UK). The car lived on the street with regular frosts and started OK every morning using XL or thicker, although crank speed modest.
I suspect the relatively thick oils originally recommended predated anti wear additives. Thick oils were also largely to reduce noise and consumption.
Presumably there are readily available inexpensive thinner oils 15W40 etc with 1980s or later API ratings.
For a low annual mileage oil burning filterless Seven, expensive synthetics a bit like “feeding chocolate to pigs”. (An expression I picked up decades ago. A very senior govt engr got into deep poo for using it to describe the proposal to use CNG for electric power generation. Which NZ did anyway. For a period it was popular here for cars. I tediously adapted my 1950s model. But cars became too complex to adapt, the power loss was considerable with moderns, and the whole vast industry collapsed before I had saved the cost of the kit!)