Oil weight

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Depends on the type of engine (race, street) and the climate of your area.
 
No, not year and size. Re-read the last reply.
 
15w40 Rotella T.

It has 1000 ppm of Zinc for the cam, and the cold viscosity reduces the load on the oil pump drive while it warms up.
 
Another oil thread started, So many opinions. Straight, with zinc additive. Or Royal Purple, or Valvoline Racing, etc.
 
I used to run Castrol GTX 20W50, back when the zinc was still there. Now it's Rotella 15W40
 
Scroll down on this link......

http://micapeak.com/info/oiled.html

Now, please note that this info is dated. I checked last year and heard that our wonderful government has limited zinc once again. Rotella use to be good but they pulled more zinc out of it. The "specialty oils" (not for street use) they left untouched. I use to swear by Rotella but on my last build I started using Valvoline Racing oil (speciality oil) because they haven't screwed with the zinc amounts.

Brad Penn oil is a winner, scroll down and read about the ZDDP results.
http://www.penngrade1.com/Zinc.aspx

Flat tappets "live" on zinc and die without it. Do the research or start saving for a rebuild. The sure cure to all these problems is to go to a roller cam.
 
I spent an entire day at the last SEMA show, chasing down Triboligists & Chemists from all of the Oil companies I could. Some would tell me more than others. I asked each of them to back up what they could with printed facts.

Mystic, Chevron, Shell & Mobil all said the same thing about Zinc. Any oil that is rated for CD-4 diesel service must contain a minimum 1000 ppm of zinc to meet the spec. Mystic showed me test reports that confirm 1300 ppm zinc in their JT8 oils. Schaeffer documents similar levels on their website. Chevron's master specification book showed 1100 ppm for Delo 400.

STP says that a single can of additive will bring 5 quarts of non zinc oil to 1000 ppm for the batch.

Now, about those pesky viscosity numbers.
Viscosity is actually measured in Centistokes, abbreviated cSt. Oils are tested at 40c & 100c temperatures. No oil gets thicker at higher temperatures.

Let's look at viscosity for several oils @40c first:

5W30 47 -52 cSt
5W40 85 - 89 cSt
15W40 102 - 108 cSt
20W50 129 - 166 cSt
30W 98 - 110 cSt
40W 130-150 cSt

Big differences, and the higher that number the harder your oil pump drive works.

Now, at 100c or operating temperature:

5W30 10 -12 cSt
5W40 13.50 - 15.5 cSt
15W40 14 - 16 cSt
20W50 16.5 - 20 cSt
30W 11.5 - 12.5 cst
40W 14.5 - 15.5 cSt

Obviously, one of them is twice as thick at operating temps than the lowest one, but the gap between a xxW40 and 20W50 is next to nothing at operating temperature.

On an engine that does not require zinc, or with a zinc additive I will run 0W40 Synthetic. No reason not to reduce the load on that pump drive.

Not an opinion, just data.

B.
 
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