The oil suitable for manual transmissions of Volvo
The only oil recommended for Volvo manufactured transmissions is that which has quality GL-1.
The teeth in the Volvo transmissions are so dimensioned that there is no need for any additives of sulphur or phosphor.
The judgement being therefore that there is hardly any advantage in using these additives.
For this reason, GL-4 and GL-5 oils are not recommended for Volvo manufactured transmissions.
The seals in the Volvo transmissions are of a very high quality and normally withstand GL-5 oils. Also the steel/molybdenum synchromesh does not appear to be particularly sensitive to this oil.
Problems can however arise at very high temperatures, such as when driving iin mountainous terrain or when the power take-off is being used. There is a risk that deposits from the oil form a coating which block the oil filter and oil channels so that the operation of the oil cooler is impaired. We therefore advise against the use of GL-4 and GL-5 oils in Volvo manufactured transmissions. The German transmission manufacturers recommend GL-4 oils. We approve therefore the use of GL-4 oils in Volvo vehicles with ZF manufactured transmissions. However even here we firmly advise against the use of GL-5 oils.
