Klubersynth GH 6-80 vs Mobil SHC Cibus 150: gear oil selection

The two products side by side

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Sources: Klüber product page for Klübersynth GH 6-80 and the Klüber product information for the GH 6 series (article number 012158); ExxonMobil product data sheet, Mobil SHC Cibus series. Both manufacturers publish guide values; confirm the documents in effect with your delivery.

Chemistry and registration decide more than viscosity

The published information for SHC Cibus 150 lists NSF H1 registration, FDA 21 CFR 178.3570 compliance, ISO 21469, and Kosher and Halal certification. The published information for GH 6-80 lists none of those; Klüber positions the GH 6 series as an industrial polyglycol gear oil with gear OEM approvals (Flender, Siemens, SEW Eurodrive, Nord and others) and worm gear optimisation. If a lubrication point needs an H1 lubricant because contact with product is possible, the H1 column decides the choice before any performance comparison starts.

Base oil chemistry also governs materials. Klüber documents GH 6 oils as resistant with specific Freudenberg seal materials (72 NBR 902 up to about 80 °C permanent temperature, 75 FKM 585, 75 FKM 170055), and notes that two-component paints and some plastics should be tested. Mobil documents good seal compatibility for SHC Cibus, including equipment normally lubricated with mineral oils. With either product, seals and coatings from a different system should be checked against the manufacturer's list before the change.

Viscosity: 68 versus 150

A VG 68 oil and a VG 150 oil are not substitutes; they fit different gear geometry and speed. The heavier oil builds a thicker film for heavier tooth loads at lower speed, at the cost of more churning heat at high speed. The gearbox manufacturer's viscosity recommendation, on the nameplate or in the manual, is the anchor. If the OEM specifies an ISO VG that neither product matches, the honest answer is that neither fits and the correct grade or a different series should be sourced.

Both oils do carry CLP-level performance. Klüber states that gears corresponding to DIN 51517-3 requirements can be switched to Klübersynth GH 6 without prior consultation with the gear manufacturer, provided the general application notes are observed, and Mobil lists DIN 51517-3 for SHC Cibus 150 as well. A CLP-class oil at the specified viscosity is the baseline both meet; the differences above it are chemistry, temperature capability and registration.

Worm gears and food plant drives

GH 6 oils were developed for worm gears with steel/bronze or steel/grey cast iron pairings: the polyglycol base oil's friction behaviour suits the high sliding contact in worm meshes, and Klüber documents low wear values per DIN 3996 and micropitting resistance for the series. That is the product's home ground.

SHC Cibus 150 documents a broader general purpose profile for food and beverage plants: enclosed gears, bearings and circulating systems, with washdown-tolerant corrosion protection and H1 documentation that simplifies audit work above or near product. For worm gearboxes inside the H1 zone, the selection question is whether an H1 registered oil at the OEM's viscosity exists for that gearbox, rather than forcing the polyglycol product into a registration it does not carry.

Changing over between them

Polyglycol oils are generally not miscible with mineral oils and synthetic hydrocarbons. Klüber's application notes for GH 6 call for lubrication points to be cleaned and systems flushed with the Klübersynth GH 6 oil before use when converting, and the product information warns that prior mineral or synthetic hydrocarbon fills must be flushed out. Treat any change in either direction as a drain, clean and flush job, then record what went in.

Common questions

Is Klübersynth GH 6-80 food grade?

Klüber's published product information for GH 6-80 does not list NSF H1 registration. Where incidental food contact is possible, specify a lubricant registered H1 and verify it in the current NSF White Book. If your gearbox must stay on a polyglycol oil for technical reasons, ask Klüber whether an H1 registered polyglycol grade exists for the application rather than assuming this product covers it.

Can I switch a gearbox from a mineral CLP oil to GH 6-80?

Klüber states that gears corresponding to CLP per DIN 51517-3 can be switched to GH 6 without prior consultation with the gear manufacturer, provided the general application notes are observed. In practice that includes the flush: polyglycol and mineral oils are not miscible, so drain, clean and flush before charging, and check the seal materials against Klüber's compatibility list.

Is the heavier VG 150 oil the safer choice?

Heavier is not safer, it is different. A VG 150 oil in a small high-speed gearbox runs hotter and wastes power on churning; a VG 68 oil in a heavily loaded slow gearbox lets the film run thin. Follow the OEM viscosity. If the OEM spec is unavailable, a lubrication engineer should size the viscosity from gear geometry, speed and temperature before either product is ordered.

Which oil for a worm gearbox near food product?

First question: does the point require H1? If yes, shortlist H1 registered gear oils at the OEM viscosity and verify registrations; SHC Cibus 150 fits that pattern at VG 150, and other grades in both brands' food ranges exist for other viscosities. If the point is outside the H1 zone and the OEM specifies CLP PG 68, the GH 6-80 class is the documented match for bronze worm gears.