From a GM service bulletin to dealers a few years ago.....

"General Motors is aware that some companies are marketing tools and equipment
to support engine crankcase flush procedures. GM does NOT endorse or
recommend crankcase flushing for any of its gasoline engines. Analysis of
some of the materials used for crankcase flushing procedures indicates
incompatibility with GM engine components and the potential for damage to some
engine seals and bearings. Damage to engine components resulting from
crankcase flushing procedures is not covered under the terms of the New
Vehicle Warranty."

So...oil and filter changes as per the owner's manual are all you need.

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Son's XC70, daughter's XC60, my 83 244DL, 89 745 (Chev LT-1 V8), and XC60. Also '77 MGB with Chev V6, and four old motorcycles. Long gone: 1981 244, 1994 940 and 1998 S90.