The Castair ROFD3-4-G11 is the OEM spin-on oil filter for Castair rotary screw compressors equipped with the D3, D31, D4, or G11 air end. These air ends are found in Castair's 5–15 HP rotary screw models — the smaller end of their rotary lineup, but still 100% duty cycle machines that demand proper lubrication maintenance. One filter part number covers all four of these air ends, simplifying what you need to stock. If your Castair rotary compressor is in the 5–15 HP range and uses a D3, D31, D4, or G11 air end, this is your oil filter.
Air End Coverage
- D3 / D31 air end: Used in 5–10 HP Castair rotary screw models. The D31 is a variant of the D3 used in certain configurations.
- D4 air end: Used in 5–10 HP Castair rotary screw models.
- G11 air end: Used in 5–15 HP Castair rotary screw models.
Check your compressor's model designation or service documentation to confirm which air end your unit carries. The oil filter part number is identical across all four, so if you have any of these air ends, the ROFD3-4-G11 is correct.
Why Oil Filtration Matters at 5–15 HP
Smaller rotary compressors often run at higher utilization rates relative to their size — a 7.5 HP rotary in a two-bay shop may run more total hours per day than a 30 HP unit in a larger facility. Continuous operation at high utilization means the oil circuit handles more thermal cycles, more particulate accumulation, and more opportunity for water contamination from air cooling. The ROFD3-4-G11 filter is your primary defense against particulate damage to the rotor bearings and timing gears in these air ends.
Maintenance Context
- Filter type: Spin-on, automotive-style paper element
-
Maintenance kits:
- MKD3-4 — for D3, D31, D4 air ends: 2 air filters (RAFD3-4), 4 oil filters (this part), 1 separator filter (RSFD3-4-6-G11-P75), 5 gallons synthetic oil — 10% savings
- MKG11 — for G11 air ends: 2 air filters (RAFG11), 4 oil filters (this part), 1 separator filter (RSFD3-4-6-G11-P75), 5 gallons synthetic oil — 10% savings
- Oil: GA4000 or FG4000 Castair synthetic rotary screw oil (1 year/4,000 hours)
- Service interval: Replace with each oil change per Castair maintenance schedule; use the standard hour meter to track
Technical Specifications
- Part Number: ROFD3-4-G11
- Filter Type: Spin-on oil filter
- Compatible Air Ends: Castair D3, D31, D4, G11
- Compatible Compressor HP: 5–15 HP rotary screw models
- Manufacturer: Cast Air
Why Buy From OEM Diagnostic Tools?
Genuine Castair OEM maintenance filters — not aftermarket substitutes. Free shipping on qualifying orders. Free tech support at 866-217-0063. Full Castair manufacturer warranty. Call us to confirm the correct filter for your specific air end.
Call 866-217-0063 for quick answers and help!
