I recently bought a bulk quantity of 5w/30 fully synthetic oil, aimed at Ford Zetecs which is ACEA rated A1/B1/A5/B5.
I was hoping to also use this in the newer Vauxhalls as well, but according to their recent manuals it states that only oils of grade A3 5w/30 should be used for all types of their engines and A1/A5 oils are "expressly forbidden as they can cause long term engine damage under certain conditions."
It seems that the A1/A5 oil has a slightly lower viscosity and is aimed at fuel efficiency but can't find a definitive answer as to why it could be damaging. The ACEA does state that this grade is not suitable for some engines, but no explanation.
Any suggestions would be appreciated, as my local motor factor wants almost double the amount for the A3 rated oil.
I was hoping to also use this in the newer Vauxhalls as well, but according to their recent manuals it states that only oils of grade A3 5w/30 should be used for all types of their engines and A1/A5 oils are "expressly forbidden as they can cause long term engine damage under certain conditions."
It seems that the A1/A5 oil has a slightly lower viscosity and is aimed at fuel efficiency but can't find a definitive answer as to why it could be damaging. The ACEA does state that this grade is not suitable for some engines, but no explanation.
Any suggestions would be appreciated, as my local motor factor wants almost double the amount for the A3 rated oil.