Originally Posted By: Shannow
Originally Posted By: d00df00d
For example:
If you pick a fuel economy oriented 0w-30 (e.g. Mobil 1 Advanced Fuel Economy 0w-30), it'll flow better on a cold start, even in a warm climate. However, being a modern synthetic that meets modern API and ILSAC specs, it should still protect better and last longer than an old 10w-30.
OK, where's your evidence for this old chestnut ?
It's not true, no matter how many people repeat it.
Per my point...the differences are all at the extreme ends of the pumpability spectrum. Have wheeled this out too many times to count
When the oil is in the pumpable range, there's no difference...
Here's some new to my library pieces...on European engine testing. First is a chart clearly indicating that the thicker oils take longer to both build oil pressure and reach the rocker arms.
Note however that the viscosity is in Poise...Whole numbers of Poise...not Centipoise.
600 Poise is 60,000Cp, which is the limiting viscosity (give or take) for each of the SAE J300 "W" bands.
Rough as gutz (because density changes the number by about 20-25%), substitute the CSt of your favourite oil for Cp...then divide by 100 to get Poise...then look at the chart, and see where they sit with regards to the 3 bar oil pressure, and the RAOT...
Pick an "even in a warm climate" temperature for your 0W20 and 10W30, lets say freezing, and draw a dot on each line where they sit in comparison to each otehr.
Authors developed a correlation...and again, it's based on the entire spectrum of very thick, nearly pumpable oils tested, not at "warm climate' temperatures.
Remember to convert to whole poise before using ... again for the test engine in question.