986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - Did a Motorflush with GUNK motorflush and change oil WOW!

blue2000s · 09-29-2009, 03:20 PM

Careful using just the rating numbers as a means in which to decided what climates to use an oil. The first number is tested at 100F, the second at 210F. The numbers are only representative of the viscosities at those temperatures. At 0F, a 5W-40 could conceivably have a lower viscosity than a 0W-40. I've seen it happen, in fact. The viscosity/temperature relationship isn't always linear in an automotive motor oil.

212 is closer to where engines run on the high side, so it's safer to directly compare the 40 rating with the 30.

09-29-2009, 03:20 PM	#43
blue2000s Porscheectomy Join Date: Mar 2006 Location: Seattle Area Posts: 3,011	Careful using just the rating numbers as a means in which to decided what climates to use an oil. The first number is tested at 100F, the second at 210F. The numbers are only representative of the viscosities at those temperatures. At 0F, a 5W-40 could conceivably have a lower viscosity than a 0W-40. I've seen it happen, in fact. The viscosity/temperature relationship isn't always linear in an automotive motor oil. 212 is closer to where engines run on the high side, so it's safer to directly compare the 40 rating with the 30. Last edited by blue2000s; 09-29-2009 at 03:34 PM.