For hydraulic fluid on a concrete driveway, the two F9 products I’d focus on are F9 Double Eagle + F9 Groundskeeper. F9 specifically lists both for oil/hydrocarbon contamination. The F9 process I'd use 1. F9 Double Eagle — first This is the heavy degreasing step. F9 specifically recommends Double Eagle for oil, grease and hydrocarbons. Their published dilutions are: Very heavy contamination: straight Heavy: 1:1–5:1 Moderate: 10:1 F9 recommends a 2–15 minute dwell, agitation on heavy areas, then surface cleaning; hot water is preferred. For a hydraulic-fluid spill, I'd probably start around 1:1 or stronger, assuming you're dealing with unsealed concrete and a substantial stain. 2. F9 Groundskeeper — second This is where it gets particularly interesting for an oil stain that has soaked into concrete. F9 says Groundskeeper is for oil and hydrocarbons, but the standing/topical oil should first be removed with Double Eagle at about 5:1. Groundskeeper is normally used around 10:1–15:1. In fact, F9 specifically describes Double Eagle followed by Groundskeeper as a “1-2 punch” on oil stains. I'd approach it roughly like this: Absorb/remove excess hydraulic fluid → Double Eagle → agitation → hot-water surface clean → Groundskeeper treatment.