The 992 engine has flat tappets. 'Old fashioned' flat tappet cams need zinc for breakin... new roller tappet cams don't.

Modern oils don't have nearly enough zinc for the old flat tappets in older hot rods and restoration auto engines. If you do run modern oil, it will wipe your cam out.

API SM is modern oil.

Soooo.. what kind of oil is correct for the 992 for breakin and regular running?

Someone with information on high-time engines would know about cam wear.
Generac says, "...Use oil of American Petroleum Institute (API) Service
Class SG, SH or SJ. Use all season SAE 5W-30
Synthetic oil. Organic break-in oil is required before
using synthetic oil..."

API says, "...the latest ILSAC standard or API Service Category includes the performance properties of each
earlier category and can be used to service older engines..."
Gas without lead destroyed old engines' exhaust valves. Gas with alcohol is now destroying all engines - they are getting rid of the 5% alcohol in Europe and going back to gasoline, because the car manufacturers are sick of the warranty work.

Oil without zinc, to save the cat converters in modern cars, is bad news for old engines with flat tappet cams. The API SM oil that was shipped with the generator is NOT to be used for breakin?

Nascar is restricted to flat tappet cams and Joe Gibbs has an oil business just for the 'old' engines... and Nascar.
willyb;8694 wrote:
...The API SM oil that was shipped with the generator is NOT to be used for breakin?...

Unless it is synthetic oil, I don't see why not. Which is it?

BTW, I doubt that Generac uses anywhere close to the spring pressures and cam lobe profile of a NASCAR engine. Something else will probably go wrong well before cam wear becomes an issue.

The thing that is destroying engines is a combination of the EPA imposing unrealistically lean mixtures, the stuff that passes for gasoline these days, and the fact that most engine makers today produce engines designed to last until the warranty expires, NOT an engine with potential to last 30+ years. Like appliance and electronics makers, they make more profit by producing products with a short lifetime, then selling a replacement every few years.
Well when it comes to the generator you must use what they specify and follow their instructions or you WILL void the warranty. They can at their option send an oil sample to a lab and have it tested.
I worked at a company years ago that did just this when one of our customers wanted to claim warranty on one of our machines but we all had serious doubts that it was properly maintained. Guess what they found?

On the other hand flat tappets in automotive engines especially during break in NEED zinc. There are ZDDP additives on the market that will fill this need. There are also custom oils that will also (Red Line etc). Some oils for diesels have various amounts of zinc also. Synthetic oil is not recommended for break-in though.