Right from Castrol oil
API GL-4 – Intended for gear sets with light to heavy load and sliding forces. GL-4 lubricants are often used in syncromesh manual shift on-road and off-road truck transmissions.
API GL-5 – Intended for heavily loaded gear sets with high sliding forces such as hypoid differentials. GL-5 lubricants contain high levels of extreme-pressure additives to provide protection under boundary lubrication conditions
API GL-4 – Intended for gear sets with light to heavy load and sliding forces. GL-4 lubricants are often used in syncromesh manual shift on-road and off-road truck transmissions.
API GL-5 – Intended for heavily loaded gear sets with high sliding forces such as hypoid differentials. GL-5 lubricants contain high levels of extreme-pressure additives to provide protection under boundary lubrication conditions
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