The Castair MKG11 Preventative Maintenance Kit covers the G11 air end (also referenced as the C11 air end on some unit labels — both names refer to the same Castair air end platform) on 5–15HP rotary screw compressors. If your compressor is in the 5–15HP range and runs a Castair G11 or C11 air end, this is the correct PM kit. It ships as a complete service bundle: two air filters, four oil filters, one separator filter, and five gallons of CAST-LUBE synthetic oil. That is everything you need for one full service interval, matched to the G11 air end specs, at a 10% discount versus buying the same parts individually.
G11 vs. C11 Air End — Clarification
- Same air end, two names: Some Castair compressors in the 5–15HP range have unit plates and manuals that reference the "C11" air end. Castair''s official parts catalog lists this platform as the "G11." If your compressor documentation says C11, the MKG11 kit is correct.
- When to call us: If your unit plate shows a different air end designation entirely, call 866-217-0063 before ordering. We will confirm compatibility against your model number.
Why Buy a Kit Instead of Individual Filters
- 10% discount vs. individual parts: Buying filters and oil as a kit saves 10% compared to individual part orders. On a $628 purchase, that is meaningful savings per service cycle.
- Complete PM coverage in one order: Air filters, oil filters, separator, and oil — all in one shipment. No partial-service situations where you have everything except the separator.
- Correct dimensions guaranteed: The G11 air filter (RAFG11) has specific dimensions (ID: 2 5/8", OD: 3 7/8", HGT: 3 1/8") that are smaller than the D62 and G30 filters. Ordering the kit means you get the right size every time without cross-referencing.
- OEM oil included: CAST-LUBE is Castair''s own synthetic formulation for rotary screw air ends. The wrong oil in a rotary screw unit — wrong viscosity, wrong additive package — shortens air end life. Using CAST-LUBE removes that variable.
Kit Components
- Air Filters (qty 2): Part number RAFG11. Paper element. ID: 2 5/8", OD: 3 7/8", Height: 3 1/8". Sized for the G11 air end — notably smaller than the D62 (RAFD6-62) and G30 (32DP) filters. Do not substitute.
- Oil Filters (qty 4): Part number ROFD3-4-G11. Spin-on design. This filter is shared across several Castair air ends: D3, D31, D4, and G11. If you have other Castair units on the same platform, these filters will cross-service them as well.
- Separator Filter (qty 1): Part number RSFLD3-4-6-G11-P75. Spin-on design. This separator is a multi-platform part — it fits D3, D31, D4, D6, P75, and G11 air ends. A shared separator means lower per-unit stocking cost if your shop runs multiple Castair platforms.
- CAST-LUBE Synthetic Compressor Oil (5 gallons): Castair''s own synthetic oil formulated for rotary screw air ends. Provides oxidation resistance and thermal stability through normal operating cycles. Five gallons covers one oil change for a unit in this HP range.
Air End Compatibility
- Primary fit: G11 air end (also labeled C11 on some units), 5–15HP rotary screw compressors
- HP range covered: 5HP, 7.5HP, 10HP, and 15HP Castair rotary screw models with G11/C11 air end
- Shared filter note: The oil filter (ROFD3-4-G11) and separator (RSFLD3-4-6-G11-P75) are used across the D3, D31, D4, D6, and P75 air ends as well. The air filter RAFG11 is G11-specific — do not use D62 or G30 air filters on a G11 unit.
What's in the Kit
- 2x Air Filter RAFG11 (G11 paper element, ID: 2 5/8", OD: 3 7/8", HGT: 3 1/8")
- 4x Oil Filter ROFD3-4-G11 (spin-on, also fits D3/D31/D4)
- 1x Separator Filter RSFLD3-4-6-G11-P75 (spin-on, multi-platform)
- 5 gallons CAST-LUBE synthetic compressor oil
Available Castair Preventative Maintenance Kits
- MKP75 — P75 Air End, 5–15HP: Two air filters (20DP), four oil filters (ROFD62-P75), one separator (RSFLD3-4-6-G11-P75), five gallons CAST-LUBE. For P75 platform units in the 5–15HP range.
- MKG11 — G11/C11 Air End, 5–15HP (this kit): $628.47. For G11/C11 platform units 5–15HP. Air filter RAFG11 is the distinguishing part — confirm your air end before ordering either MKP75 or MKG11.
- MKD62 — D62 Air End, 15–25HP: $704.70. For mid-range 15–25HP units. Larger air filter (RAFD6-62, OD: 6 1/8") than the G11 kit. Step up if your unit is in the 15–25HP range.
- MKG30R — G30 Air End, 15–30HP: For larger G30 platform units. Air filter 32DP (OD: 9 1/4") is substantially larger. For 15–30HP G30 units.
All four kits save 10% vs. individual parts. If you are unsure which air end your compressor has, call 866-217-0063 with your model number.
Filter Reference — G11 Air End Individual Parts
- Air Filter: RAFG11 — ID: 2 5/8", OD: 3 7/8", HGT: 3 1/8" — G11 paper element
- Oil Filter: ROFD3-4-G11 — spin-on, also fits D3/D31/D4
- Separator Filter: RSFLD3-4-6-G11-P75 — spin-on, fits D3/D31/D4/D6/P75/G11
- Oil: CAST-LUBE synthetic, available in 5-gallon jugs
When Does a Shop Need This Kit
- You have a 5–15HP Castair rotary screw unit with a G11 or C11 air end coming up on its service interval. The MKG11 is the correct PM kit — stock it and service on schedule.
- You see "C11" on your unit plate: The MKG11 is the right kit. The C11 and G11 designations refer to the same air end. Call us if you want to confirm before ordering.
- You run a small shop compressor hard: A 10–15HP rotary screw running near-continuous duty cycles needs on-schedule PM to protect the air end. Having the kit on the shelf before you need it prevents emergency downtime.
- You run multiple Castair units on the same platform: The oil filter and separator in this kit are shared across D3, D31, D4, D6, and P75 air ends. Stocking the MKG11 gives you filters that also cover other units in your shop.
- Step up to MKD62 instead if your unit is a 15–25HP machine with a D62 air end. The D62 requires larger air filters — you cannot use RAFG11 on a D62. Confirm your air end before ordering.
- Step up to MKG30R instead for 15–30HP G30 air end units. The G30 uses a significantly larger air filter (32DP) and different oil filter (ROFD16-G30).
Technical Specifications
- Kit Part Number: MKG11
- Air End: G11 (also labeled C11 on some unit nameplates)
- HP Range: 5–15HP rotary screw compressors
- Air Filter P/N: RAFG11
- Air Filter ID: 2 5/8"
- Air Filter OD: 3 7/8"
- Air Filter Height: 3 1/8"
- Air Filter Type: Paper element
- Air Filter Qty in Kit: 2
- Oil Filter P/N: ROFD3-4-G11
- Oil Filter Type: Spin-on
- Oil Filter Also Fits: D3, D31, D4 air ends
- Oil Filter Qty in Kit: 4
- Separator Filter P/N: RSFLD3-4-6-G11-P75
- Separator Filter Type: Spin-on
- Separator Also Fits: D3, D31, D4, D6, P75 air ends
- Separator Filter Qty in Kit: 1
- Oil Type: CAST-LUBE synthetic compressor oil
- Oil Qty in Kit: 5 gallons
- Kit Price: $628.47
- Savings vs. Individual Parts: 10%
- Manufacturer: Castair (Cast Air)
Why Buy From Air Compressor Factory Direct?
- Compressor parts specialists: We stock the full Castair maintenance kit lineup and know which kit matches which air end. The G11/C11 naming issue is a common point of confusion — we can verify your unit before you order.
- Free shipping: The MKG11 ships free. Five gallons of synthetic oil plus filters is not a light shipment — free shipping is real savings on parts orders of this type.
- Free tech support: Call 866-217-0063 before ordering if you have any question about whether your unit has a G11/C11 or a different air end. We confirm compatibility before you spend $628.
- Full manufacturer warranty: Castair OEM parts with full Castair warranty coverage. No aftermarket substitutes.
- Honest recommendations: If the MKG11 is not right for your machine, we will point you to the kit that is. We sell parts correctly the first time.
Call 866-217-0063 for quick answers and help!
