Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec what oil weight does everyone use?

Just remember, as long as the oil can be provided to every component under all conditions, that's with tight tolerances and all, then it is sufficient.
I still can't imagine using a 0 weight oil unless I lived in Montana or something.
Also, those relative weights are not really accurate. The weight of the base oil is the first number. The second number indicates the thinning resistance. Thinning being a bad property for oils and the reason they add additives. The polymers help reduce thinning. THe thinning resistance of a heavier oil is the best, but its low temp properties will kill a motor, hence the multi-weight.

20w-50 oil is a 20weight oil that won't thin more than a 50wt at high temperature. It doesn't gain oil weight.

Here is a good URL explaining it and some brief quotes:
Multi Grade Oil explanations

Quote:

---

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

---

Quote:

---

Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you are going to encounter. In the winter base your decision on the lowest temperature you will encounter, in the summer, the highest temperature you expect. The polymers can shear and burn forming deposits that can cause ring sticking and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives. Oils that can do their job with the fewest additives are the best.

---