Trollbait
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- Vehicle Year
- 2000
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- Ford
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Actually, liquids get thinner when heated up. The multi-viscosity motor oils contain additives that keep it from thinning out too much, but it's still thinner at operating temp than at cold.i thought the light weight was for when its cold, so its easier to start, than thickens when it reaches operating temp? i remember my owners manual has a chart, it recommends 5w30 for where i live (-20 to 90deg)(not exact, i cant remember) and 10w30 and so on, in warmer climates. do they not apply this anymore? i know toyota, you can run 0w20, warmer you can run 5w20.
Something to keep in mind, the Xw-XX on a bottle of oil is just a labeling system. Those numbers don't equate directly to any actual measured viscosity of the oil.
You can find the actual tested viscosity at the bottom of these pages.
http://www.mobiloil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil1_5W-30.asp
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_5W-20.asp
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_0W-20_Advanced_Fuel_Economy.asp
http://www.mobil.com/USA-English/Lubes/PDS/GLXXENPVLMOMobil_1_0W-30_Advanced_Fuel_Economy.asp
The operating temp viscosities of the 30s are 11cSt (centistokes, water is around 1 at room temp), and the 20s are near 9cSt.
Now the cold tested viscosities are close between the 0 and 5, but differ between the 20 and 30. The 20s are in the high 40s for cSt, and the 30s are in the low 60s.
The cold test in only cold in relation to the hot test though. It's done at 104F. So the difference between 0 and 5 will likely grow the colder it gets.
To sum up. Light weight motor oil is thicker than water. In a warmed up engine, the 30s and 20s are close. While warming up, the 20 is noticeably thinner than the 30, which will allow it to be pumped through the system easier, and with less time through the filter bypass valve. The difference between 5 and 0 likely only comes into effect when it is truly cold out at start up. The 0s are only available as synthetics, so they have that advantage.