Shock oil weight is the viscosity rating of the silicone oil in an RC shock. It's labeled two ways — "wt" (weight) and cSt (centistokes) — and thicker oil slows suspension movement.
cSt is a real viscosity unit; “wt” is a legacy label manufacturers apply inconsistently, so the same “wt” number can be a different actual viscosity from brand to brand. Most US brands land near cSt × 0.1 — So Dialed puts 30wt at roughly 300 cSt — but EuroRC warns those labels “aren’t directly comparable between manufacturers.” That’s why racers compare cSt when crossing brands, and why the standard advice is to run one brand in all four shocks. Rough baselines in cSt: 1/10 touring around 400 front and rear; 1/10 2WD buggy roughly 300–350 front and 250–350 rear; 1/8 buggy about 450–500 front and 400–450 rear. Thicker for smooth and high-grip, thinner for rough.
Buy oil by the "wt" number across two brands and you can end up with four shocks that aren't actually matched, which makes every other setup change you test a lie.