Gear oil
Detergent additives are the norm for multi-grade engine oil but I don't believe that 80w-90 gear oil has any detergent. Anti wear, anti foam and corrosion inhibitor but no detergent. Detergents in motor oils generally are used to keep the by- products of combustion in control. I can't see any problems using 80w-90 or 80w-140 in the gear box or axles in older vehicles.
Paul
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