Question: “Is Spectro Heavy Duty 6-Speed GL-5 transmission oil safe for yellow metals (bearings, bushings) in the transmission? Your data sheet indicates a GL-5 rating. Some discussions, including the Mobil-1 website, state that the additives in GL-5 oils are detrimental to “yellow metal” parts in the transmission. Is your GL-5 transmission oil different?”
Answer: “Spectro 6 Speed is GL5 rated but is safe to use in GL1 applications. We use a different formula (developed by Spectro) than other brands that is buffered. This formula will not attack “bright” metals such as brass, bronze and copper found in older transmissions. It’s more expensive to produce, but we feel the performance is well worth the cost. It also improves shifting in most applications, reduces noise (5th gear whine in HD 6 speeds) and is highly resistive to shear and loading. Spectro Oils Of America.
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