Old engine new oil?

I bought a car that has been sitting 16 years.  Build thread soon. 

Maybe after 16 years I oughta change the oil, even though it's not black yet.  :-) 

It's a Chevy small block, a cast iron 350 out of a '73 Camaro or thereabouts.  Appears stock.  

My question is what oil to put in it?  My first thought was to put in some motor flush product, idle it a while, (yes it runs)  then drain it and use my usual go-to 5w40 full synthetic oil.  But some folks think a modern high detergent full synthetic might not be good in an older engine ...?  Although synthetics came out in the 70's and detergent multiweight oils even earlier than that.  I have no idea what the PO might have used.

What would you do?

15w40 Diesel 

You've got a flat tappet cam in there and modern oils don't have a good enough zinc content to keep the cam alive. 

Diesel oils have a heavier additive package.

Or, 10w30 like the mfg suggests and a bottle of GM engine oil supplement. 

I always ran Rotella (engine oil for diesels) in my older SBC.  I used that even when road racing.

I use Lucas hot rod and classic in my Sprite. High zinc, keep the cam happy.

If the oil in there looks clean, and comes out clean, I would likely send it.   If not, change after 500 miles if you are really worried. 

Use something specific for flat tappet cams with high ZDDP. There are many produxts available at a reasonable price. The new HDEO's don't have the zddp that the older oils had and are not as effective, as well as may be too thick for the engine. 

Do not use a flush until you know what's going on. A flush can be useful in an engine that is severely sludged, but just sitting for 16 years, the bigger issue you're going to have is rust. Whatever you choose, be sure to put some oil down in the cylinders before turning the engine over to give the rings a chance. Otherwise, the rings will wear substantially trying to clean the rust off the bores while trying to seal the cylinder. 

Myths about synthetic oils in old engines are just that, myths. If you choose to go synthetic, make sure it offers the type of protection that engine requires. 

Apexcarver said:

I use Lucas hot rod and classic in my Sprite.

I ran Lucas Hot Rod oil in my flat-tapped 11:1 '77 Silverado for the first two years after building it, and found it just got noisy quickly, like in 1000 miles quickly. I even sent a sample to Blackstone Oil Labs, who noted it was getting rather thin (link-to-their-report).

I switched to Rotella (plus zinc additive just for good measure) and never went back.

I'll 3rd or 4th Rotella. I run it in everything built before the 1990s as well as lawnmowers, 4-wheelers, SBSs, and boats. 

SkinnyG (Forum Supporter) said:

Apexcarver said:

I use Lucas hot rod and classic in my Sprite.

I ran Lucas Hot Rod oil in my flat-tapped 11:1 '77 Silverado for the first two years after building it, and found it just got noisy quickly, like in 1000 miles quickly. I even sent a sample to Blackstone Oil Labs, who noted it was getting rather thin (link-to-their-report).

I switched to Rotella (plus zinc additive just for good measure) and never went back.

I don't usually recommend/not recommend oils to people because there's hardly a poor choice, but I have a hard time recommending most of their products.... and they're a local company. 

In reply to bobzilla :

Lucas or Shell?

Rotella is like Frank's Red Hot

In reply to ShawnG :

Either to be honest, but the former for sure. Great marketing company that offers pertoleum products. 

Rotella is just used when it doesn't need to be so often and there are better options. Not to mention there used to be 6 different "rotellas" on the market and they are vastly different. 

In reply to SkinnyG (Forum Supporter) :

Good to know!  will switch it up then. 

Valvoline ZR1, Castrol GTX Classic, Penn Grade, Driven, Amsoil Z-rod are all good options for gasoline engines needing high zinc. 

I think this engine has hydraulic lifters?  But I get it, flat faces not rollers. 

Yeah my default is Rotella T6 synthetic 5w40.  They used to list that for gas as well as diesel engines but the latest bottles have removed the SN or was it SM.  But they still carry the rating for motorcycle engines which are gas four strokes.

Or if I don't want synthetic I could use the 15w40 Rotella, I think it is T5?  Castrol GTX is of course a classic from back in the day too.

Sounds like the consensus above is the not-synthetic Rotella?  That's fine with me, the engine is understressed in stock form in a lightweight car, and it's not going to get driven in winter or for high miles. 

Use whatever you can find that's closest to the beginning of the alphabet on the API cert, or preferably doesn't have one. The "Sx" designation is continually updated with the latest preferences of the OEMs, EPA, API (as a for-profit organization) and the unnamed evil deep state orgs that we all know really run the show... Nowadays, the newer the API cert, the "cleaner" the oil will burn by having removed the secret sauce that made it good for old stuff. The differentiator for engines is high-pressure sliding contact, as in flat tappet cams of any kind. There is a level of contact pressure and surface speed at which every oil will cease to provide adequate film strength and residual deposits to resist wear, depending on the specific interface design, materials and surface condition, environment, and loading. The oil needs to be matched to the task or sadness will result, end of story. There is no magic.

The sticking point here is that whatever your favorite used to be--if it was bought OTC--it's now a totally different oil following the API prescription, so historical references are invalid. If you have bottles of Rotella T4 from 20 years ago, it's liquid gold, and run that. Check the dipstick in that old SBC and it will say "USE ONLY GRADE SE OIL" or some such paraphrase. We're now at API SN for street oils. ZDDP and all the other goodness in oil can be replaced to some degree with additives.

Personally, I've had good results running Driven HR-series oil in my old iron (the race car gets the GP-1). It does not carry an API cert and therefore does not meet current emissions best practices, but neither do my engines it runs in. It is a specific-purpose product designed for the type of loading and wear in an older pushrod motor and saves you the trouble of sourcing additives.

Don't bother with a flush unless it's contaminated with water or sludgey.