What engine oils are you guys running?!

[Liberty]

I just run plain jane Pennzoil 10W-30 in my 82 with a 350.

[hatzie]

I looked in the service manuals for giggles...
-------------------
The 1973 GM Recommended Viscosity usage;

• SAE 30W from 40°F to 85°F
• SAE 5W30 from -35°F to 65°F
• 10W40 from -10°F to 105°F
• 15W40 from -5°F to 105°F

NOTE: SAE 5W-20 oils are not recommended
for sustained high-speed driving.
SAE 30 oils may be used at temperatures
above 40°F.
---------------------

Modern charts place Group III and Group IV 5W40 synthetics in the -35°F to 90°F range and 5W50 oils in the -35° to 105°F range. The wider bearing tolerances in the older GM engines will do just fine with 10Wxx or 15Wxx oil.
Re-builds????
If you rebuilt it on the tight side of the tolerances then you probably want a lighter weight Group III or Group IV synthetic oil for cold starts after the first 5,000-7,500 miles... so a 0W40 or 5W40 or even 5W50 is the way to go. If it's on the loose side then 10W40 or 15W40 made from dead dinosaurs will do just fine. The nice thing about synthetics is they tend to run cleaner and they aren't wildly expensive anymore.

Look up some Virgin Oil Analysis (VOA) sheets for the oil you're looking at using. They'll tell you what levels of anti-wear and detergent elements are in the add pack of your shiny new bottle of oil.
UOA Used oil analysis sheets will tell how effective the brew of anti wear and detergent additives are.
I personally like a stout amount of Zinc and Phoshphorous 1,100 PPM or better of both. That's why I lean toward the diesel oils that still retain the API S ratings as well as the API C ratings.

Here's what each element in the analysis tells you. Higher wear metals are obviously bad. More detergent and anti-wear elements are good... The other thing to keep in mind is "did the viscosity shear down a lot over the change interval?"... When you find that the oil is still the same 10W40 or 5W40 or... when you drain it is where better base stocks shine.

Aluminum- Pistons, Bearings, Cases (Heads and Blocks)

Chromium- Rings, trace element in steel.

Iron- Cylinders, rotating shafts, valve train, and any steel part sharing the oil.

Copper- Brass or Bronze parts, copper bushings, bearings, oil coolers, also an additive in some engine oils.

Lead- Bearings.

Tin- Bearings, bronze parts, piston coatings.

Molybdenum- Anti-wear additives, some type of piston rings.

Nickel- Trace element of steel, plating’s on some cylinder types.

Manganese- Trace element, additive in gasoline.

Silver- Trace element, some type of bearings.

Titanium- Trace wear metal, additive in some oils, Rods, Valve types.

Potassium- Anti-Freeze, additive in some oils.

Boron- Detergent/ dispersant additives.

Silicon- Airborne dirt, sealers, gaskets, lubricants, antifreeze inhibitor.

Sodium- Anti-Freeze, additive in some oils.

Calcium- Detergent/ dispersant additives.

Magnesium- Detergent/ dispersant additives.

Phosphorus- Anti-wear additive.

Zinc- Anti-wear additive.

Barium- Anti-wear additive.

This is a Blackstone Mobil 1 UOA on an LS7
Antiwear element levels look like a racing formulation.


Blackstone Rotella T6 UOA on a WRX Turbo
Note the elevated wear metals in the first 7500 miles that leveled off at a lot less in the subsequent changes. Shows what happens during break in.

[Zach079xxx]

Thanks!! It's so cool seeing the old time stuff!

Originally Posted by hatzie

I looked in the service manuals for giggles...
-------------------
The 1973 GM Recommended Viscosity usage;

• SAE 30W from 40°F to 85°F
• SAE 5W30 from -35°F to 65°F
• 10W40 from -10°F to 105°F
• 15W40 from -5°F to 105°F

NOTE: SAE 5W-20 oils are not recommended
for sustained high-speed driving.
SAE 30 oils may be used at temperatures
above 40°F.
---------------------

Modern charts place Group III and Group IV 5W40 synthetics in the -35°F to 90°F range and 5W50 oils in the -35° to 105°F range. The wider bearing tolerances in the older GM engines will do just fine with 10Wxx or 15Wxx oil.
Re-builds????
If you rebuilt it on the tight side of the tolerances then you probably want a lighter weight Group III or Group IV synthetic oil for cold starts after the first 5,000-7,500 miles... so a 0W40 or 5W40 or even 5W50 is the way to go. If it's on the loose side then 10W40 or 15W40 made from dead dinosaurs will do just fine. The nice thing about synthetics is they tend to run cleaner and they aren't wildly expensive anymore.

Look up some Virgin Oil Analysis (VOA) sheets for the oil you're looking at using. They'll tell you what levels of anti-wear and detergent elements are in the add pack of your shiny new bottle of oil.
UOA Used oil analysis sheets will tell how effective the brew of anti wear and detergent additives are.
I personally like a stout amount of Zinc and Phoshphorous 1,100 PPM or better of both. That's why I lean toward the diesel oils that still retain the API S ratings as well as the API C ratings.

Here's what each element in the analysis tells you. Higher wear metals are obviously bad. More detergent and anti-wear elements are good... The other thing to keep in mind is "did the viscosity shear down a lot over the change interval?"... When you find that the oil is still the same 10W40 or 5W40 or... when you drain it is where better base stocks shine.

Aluminum- Pistons, Bearings, Cases (Heads and Blocks)

Chromium- Rings, trace element in steel.

Iron- Cylinders, rotating shafts, valve train, and any steel part sharing the oil.

Copper- Brass or Bronze parts, copper bushings, bearings, oil coolers, also an additive in some engine oils.

Lead- Bearings.

Tin- Bearings, bronze parts, piston coatings.

Molybdenum- Anti-wear additives, some type of piston rings.

Nickel- Trace element of steel, plating’s on some cylinder types.

Manganese- Trace element, additive in gasoline.

Silver- Trace element, some type of bearings.

Titanium- Trace wear metal, additive in some oils, Rods, Valve types.

Potassium- Anti-Freeze, additive in some oils.

Boron- Detergent/ dispersant additives.

Silicon- Airborne dirt, sealers, gaskets, lubricants, antifreeze inhibitor.

Sodium- Anti-Freeze, additive in some oils.

Calcium- Detergent/ dispersant additives.

Magnesium- Detergent/ dispersant additives.

Phosphorus- Anti-wear additive.

Zinc- Anti-wear additive.

Barium- Anti-wear additive.

This is a Blackstone Mobil 1 UOA on an LS7
Antiwear element levels look like a racing formulation.


Blackstone Rotella T6 UOA on a WRX Turbo
Note the elevated wear metals in the first 7500 miles that leveled off at a lot less in the subsequent changes. Shows what happens during break in.

[tucsonjwt]

Looks like I need to stop driving my truck when it gets over 105 degrees in AZ.
That means it will be parked all summer.

[hatzie]

Originally Posted by tucsonjwt

Looks like I need to stop driving my truck when it gets over 105 degrees in AZ.
That means it will be parked all summer.

That's what you get for living on the edge of the 9th circle.

20W50 is on the GM chart on that page. I didn't copy the info. 10°F to 120°F is what other charts say for 20W50.
GM was fairly conservative in the service manual chart. I would think you can get away with 10W40 but they weren't willing to say so back then.

[Shifty One]

Lucas 10/40 semi-synth...

[beamn7]

I run Schaeffer's 10w30. Got turned onto it by some of our fleet customers that were running old P vans with flat tappet smallblocks. 200+k miles, tore a couple down and looked like new. Virtually no wear on lubricated components. Thought it was snake oil at first but tear down sold me on it.