I would have expected to find some old posts on motor oil but I didn't see any searching the archives.

I have a 91 Formula, TPI 350, 36k miles. I am the new owner.

The owner's manual recommends 5W-30 or 10W30, no issue there. But with so many varieties and brands of modern motor oils I was curious as to what are in common use among Gen 3 owners.

I have three other vehicles with various oil recommendations:

2018 Mazda - Castrol GTX 5W30 synthetic blend
2021 Chevy Colorado V-6 Mobil 1 5W30 Dexos 2 synthetic
1977 Jeep Cherokee - Brad Penn 15W40 good old-fashioned Pennsylvania oil

The Brad Penn oil has a high zinc content and is popular among drag racers. In my well worn high mileage Jeep I figured it would be a good match. I am inclined to use Brad Penn it in the Firebird too, but I am also considering Mobil 1.

If you have any thoughts or an educated/experienced opinion I would like to hear from you.

 

Valvoline Maxlife 10w-30 is what's in my tired L98. It has important features such as:

• America colors
• Jug has a molded pour spout
• Maxes lives

 

I just use whatever high mileage oil is on sale from Amazon in the gallon size. Usually MaxLife. My car has well over 100K though, I'd probably use a standard oil if it had low miles.

 

I use 10w-40 conventional usually napa brand, i get a nice discount.

 

My , use the Brad Penn and substitute a quart or two with a lighter weight full synthetic. WalMart brand will work for that.

 

For a basic street engine, there's nothing wrong with inexpensive walmart oil. Oil is the life blood of an engine. Unless you have a modern newer vehicle with tight tolerances, electronic fuel management systems and synthetic oil which can extend the oil life, just change your oil and filter on a regular basis. 3000 miles or 5000 km should be the limit on conventional oil. If you want to go with synthetic oil then 5000/8000 should be the limits. That increased distance doesn't really justify the increased cost of the oil however the synthetic oil is better for the engine plus it also makes cold winter starts much easier.

 

Any of it is good if you keep it changed. Conventional oil now is light years better than it used to be

 

Engines with roller cams are not picky about motor oil as long as it's the proper viscosity. Use a viscosity that produces a sufficient hot oil pressure at idle. The "3,000 mile" oil change recommendation applies to older, carbureted engines. Fuel injected engines can safely go farther between changes. Doesn't matter if it's synthetic or conventional. My modern daily-drivers get an oil change at 4,000 miles, which is still 1,000 miles sooner than the factory recommendation (it still looks clean at 3,000 miles). For the flat-tappet engines, I'd use Valvoline or Havoline conventional, or Quaker State (which is really Shell) Ultimate Durability synthetic, and use a ZDDP additive for either type...

 

Per the FSM for a SBC at full operating temperature, minimum pressures. If the engine is at factory clearences 5w30 should have no trouble achieving those pressure readings.
6 psi @ 1,000 rpm,
18 psi @ 2,000 rpm
24 psi @ 4,000 rpm

 

Wow, those seem like really low pressures. I get nervous if there's less than 20 psi at 650 RPM,
and of course we've all heard that "rule of thumb" about 10 psi increase for every 1,000 RPM increase above idle...

 

I haven't noticed any new oil topics for a long time, but this site should be rich with them.

Personally, for a newly acquired, 36,000 mile, 31-year-old SBC, I'd suggest a high mileage oil to keep it in excellent condition "forever." Substitute one quart for an oil that's high in zinc, if you want that.

High mileage oils will make an old engine perform like new again, and they'll keep new engines from aging "normally." Given the way SBC components age, it's as if high mileage oils were created specifically for them--and they probably were.

I grew-up with Valvoline, so I've been using Valvoline Max Life since it came out, which was around 2000-ish. I believe it was the first high mileage brand. It's kept my Formula's engine in excellent running condition.

I've also been using Max Life in all of my other cars and trucks since their first oil change, all of which I purchased new(only new for me; can't tolerate the stenches in used vehicles; not saying any of you stink, but...). My 2000 commuter car had over 200,000 miles on it when I gave it to a co-worker in 2006. My 2006 truck had 309,000 miles and still ran like new when I gave it to a friend in 2015(changed factory-original plugs at 300,000 miles, but they still looked good); he still drives it today. And my current 2015 truck has 384,000 miles and still runs like new(still on its factory-original spark plugs--engine's never been opened-up for anything; gas, not diesel); should surpass 400,000 before year's end. All on Max Life, exclusively, full synthetic since it's been available that way, which it wasn't always.

Any weight will be fine too, providing it's suitable for your geographic region, but the recommended 5W-30 or 10W-30 is great most everywhere.