{"product_id":"castair-cast-lube-rotary-varnish-cleaner-multi-grade-semi-synthetic-oil-for-piston-air-compressors-1-quart-qt5w30","title":"Castair CAST-LUBE Rotary Varnish Cleaner Multi-grade semi-synthetic oil for piston air compressors 1 quart QT5W30","description":"\u003cp\u003eCastair CAST-LUBE QT5W30 is a 1-quart, 5W-30 multi-grade semi-synthetic oil for piston air compressors. At $11.55 per quart, it is the more economical option in the CAST-LUBE piston oil lineup. It carries a 4-month or 400-hour service rating and a -37°F pour point. The QT5W30 is factory-approved for Castair piston compressors and is the correct oil for shops that follow regular maintenance schedules and want quality oil at the lower price point. For extended drain intervals, step up to the QT10W30 full synthetic at $25.41 with its 800-hour rating.\u003c\/p\u003e\n\n\u003ch2\u003eAbout CAST-LUBE Semi-Synthetic\u003c\/h2\u003e\n\u003cp\u003eThe QT5W30 is engineered specifically for piston air compressor pumps. It addresses the specific failure modes of reciprocating compressor lubrication: high-temperature oxidation that breaks down conventional oil between service intervals, foaming from air entrainment that disrupts the oil film on cylinder walls, varnish buildup that sticks ring grooves and deposits on valve seats, and cold-start viscosity failure in unheated shops. The -37°F pour point means this oil flows at cold startup in a Minnesota shop in January without pre-heating — cold-starting a compressor with oil that is too thick for ambient temperature is a primary cause of premature pump wear on cylinder walls and bearings.\u003c\/p\u003e\n\n\u003ch3\u003eKey Specifications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e QT5W30\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize:\u003c\/strong\u003e 1 quart\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGrade:\u003c\/strong\u003e 5W-30 multi-grade semi-synthetic\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePour point:\u003c\/strong\u003e -37°F\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eService rating:\u003c\/strong\u003e 4 months or 400 hours\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eApplication:\u003c\/strong\u003e Piston air compressors\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $11.55\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eOil Properties\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eSemi-synthetic formulation:\u003c\/strong\u003e Synthetic base oil with conventional oil blend for cost-effective performance\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh temperature rated:\u003c\/strong\u003e Maintains viscosity at piston compressor operating temperatures\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eLow carbon:\u003c\/strong\u003e Reduces carbon deposits on valve seats and piston crowns between service intervals\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eNon-foaming:\u003c\/strong\u003e Anti-foam additives prevent oil foaming from air entrainment in the crankcase\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eAll-season multi-grade:\u003c\/strong\u003e 5W cold-flow rating at -37°F with 30-weight high-temp protection\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eUniversal piston application:\u003c\/strong\u003e Compatible with standard piston compressor designs\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eFactory approved:\u003c\/strong\u003e Specified by Castair for piston compressor maintenance\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eCAST-LUBE Full Product Lineup\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eQT5W30\u003c\/strong\u003e — 1 qt, 5W-30 semi-synthetic, 400 hrs \/ 4 months ($11.55) — this unit\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGA5W30\u003c\/strong\u003e — 1 gal, 5W-30 semi-synthetic, 400 hrs \/ 4 months\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eQT10W30\u003c\/strong\u003e — 1 qt, 10W-30 full synthetic, 800 hrs \/ 8 months ($25.41)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGA10W30\u003c\/strong\u003e — 1 gal, 10W-30 full synthetic, 800 hrs \/ 8 months\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGA4000 \/ FG4000\u003c\/strong\u003e — Full synthetic for rotary screw compressors, 4,000 hrs \/ 1 year (do not use in piston compressors)\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eRotary Varnish Cleaner — When to Use It\u003c\/h2\u003e\n\u003cp\u003eCastair sells a companion cleaner called Varnasolv. If you are servicing a compressor that has been running conventional motor oil or has visible varnish buildup in the crankcase, the transition protocol is: mix Varnasolv at 10% with the current oil charge, run for 50 hours, then drain warm and change the oil and separator filters. Do not run Varnasolv indefinitely — it is a one-time cleaning treatment, not a lubricant additive. After the cleaning cycle, refill with the appropriate CAST-LUBE grade.\u003c\/p\u003e\n\n\u003ch2\u003eQT5W30 vs. QT10W30 — Choosing the Right Grade\u003c\/h2\u003e\n\u003cp\u003eFor a shop compressor running moderate hours with consistent maintenance schedules, the QT5W30 does the job at the lower price. Change it every 4 months or 400 hours and you are covered. The step up to QT10W30 makes sense when: your compressor runs 6+ hours per day, you want to service it less frequently (8 months instead of 4), or your shop environment is hot enough that extra thermal stability matters. Both are correct for Castair piston compressors — the difference is service interval, not oil suitability.\u003c\/p\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003ePart Number:\u003c\/strong\u003e QT5W30\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eManufacturer:\u003c\/strong\u003e Castair (Cast Air)\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eType:\u003c\/strong\u003e Semi-synthetic piston compressor oil\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eGrade:\u003c\/strong\u003e 5W-30 multi-grade\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSize:\u003c\/strong\u003e 1 quart\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePour point:\u003c\/strong\u003e -37°F\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eService interval:\u003c\/strong\u003e 4 months or 400 hours\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003ePrice:\u003c\/strong\u003e $11.55\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eWhat's in the Box\u003c\/h2\u003e\n\u003cul\u003e\n\u003cli\u003e1x 1-quart bottle of Castair CAST-LUBE 5W-30 semi-synthetic piston compressor oil\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch3\u003eWhy Buy From Air Compressor Factory Direct?\u003c\/h3\u003e\n\u003cp\u003eFactory-specified oil matters for compressor longevity. Generic 10W-30 motor oil from the auto parts store is not formulated for piston compressor duty — the anti-foam package differs, the thermal stability rating differs, and compatibility with valve seat materials may vary. We stock the full Castair CAST-LUBE lineup so you can maintain your equipment with the correct product. Free shipping on qualifying orders. Call us if you are unsure which grade your compressor requires.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eCall 866-217-0063 for quick answers and help!\u003c\/strong\u003e\u003c\/p\u003e","brand":"Cast Air","offers":[{"title":"Default Title","offer_id":53342498029781,"sku":"QT5W30","price":21.3,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0622\/8466\/0949\/files\/360_F_473254957_bxG9yf4ly7OBO5I0O5KABlN930GwaMQz_4c65e112-e309-42f5-a884-4521df1ba433.jpg?v=1772652427","url":"https:\/\/aircompressorfactorydirect.com\/products\/castair-cast-lube-rotary-varnish-cleaner-multi-grade-semi-synthetic-oil-for-piston-air-compressors-1-quart-qt5w30","provider":"Air Compressor Factory Direct","version":"1.0","type":"link"}