Looking for Oil recommendations...

[bobcowan]

An oil molecule is the same size and weight, always. It never changes. No matter what the brand or viscosity, the oil molecule is the same size and weight. That's a constant. Just like any other molecule. To change the size/weight, you need to add or subtract atoms. When you do that, you create a new substance. That's basic chemistry.

Nowhere in that article does it mention molecular weight.

SAE grade's the oil rating on it's viscosity at a specific temperature. That's it. that's all it's based on - viscosity. The ratings change a bit through the years as oils and engines advance. But it's still based on viscosity.

The manufacturer's change the viscosity with additives, as said above. That doesn't change the basic molecule, but does change the solution. Like making kool-aid.

[scottj]

SAE defines the measurement of the viscosity.

Viscosity is defined or determined by the molecular weight.

Mineral oil molecules are not all the same. The molecules vary in structure, size, and weight. It is the average weight that determines viscosity.

Synthetic oil molecules are all identical.

[Bod]

I'm on a very steep learning curve here.Thanks to all you knowledgable gentlemen. Would the oil filter have to be changed for different oils ?
Cheers Jeff

[bobcowan]

The oil filter gets changed whenever you change the oil.

4qts of clean oil + 1qt of dirty oil = 5qts of dirty oil.

[Bod]

Thanks Bob
I should have said differenf Viscosity oils
Jeff

[bobcowan]

You should still change the filter, even if you're draining "clean" oil just for a viscosity change. The filter contains 1/2- 1 qt of oil, and you don't want to mix any more of the old oil than you have to.

As for the filter type, use the best one you can find, always. But you don't need a different type or brand of filter for different viscosities. I prefer a Purolater Pure-1 or Motorcraft.

[CBattaglia]

My oil pressure is at 75 psi when cold. That seems to be too much. I ran joe Gibbs HR 20-50. I just bought HR 15-50 and will see if that number comes down some. Im at around 30 psi when hot.

[Bobcat]

IMO , 75 psi cold isn`t too high . Mine runs 80 to 85psi cold , 57to 60 psi at 200 degrees oil temp and 35 to 40 at idle , hot . I run 15W - 40 Brad Penn street and track . Is that 30 psi at idle or another rpm ?
Since you`re up North where it gets a little colder than here ( SC ) , you may want to go with a 10W - 40 for Fall and possibly 10W - 30 for Winter .
Just a thought .

[RET_COP]

Theres not much difference between 20-50 and 15-50 when HOT, they both behave the same.
I found about a 5 lb. difference in oil pressure between 15-50 and 10-30 Gibbs Hot Rod oil HOT. I also noticed a difference in temperature between the two. In my SBF the 30W ran 5 degrees cooler than the 50W. I'm staying with the 10-30.