5W50 Mobil 1 for a 156k T5?
 

Whilst attempting to clear some 'junk' from the garage I came across eight litres of Mobil 1 5W50 full synthetic oil, and wondered whether it could be used in the C70 (2000 model year):confused_smile:

My first thought is that the '50' weight is a bit too high for the engine when at normal temperature, but might benefit this higher-mileage engine.

10W40 semi-synth seems like most people's choice, which I have no problem with - probably just a bit of 'Scrooge McDuck' creeping in....:angel_smile:

Definitely, I'm using it in all my petrol volvos for years.

5W/50 compared to 5W/30
 

If you've got this synthetic oil - use it. It won't do any harm, as it will give a slightly heavier coating on moving parts.

It all depends how clean your engine is now after 156,000 miles. If you've always changed every 10,000 miles / annually, it should be clean without blockages anywhere to get clogged with a slightly thicker oil.

In terms of 'weight' of the oil I've come round to the way of thinking that the significant figure for that is the lower one, the 5w means it's light enough to flow well even when cold, the 50 means it won't turn to water when the engine gets hot. The 10w 40 would meet spec and 10 is thin enough to flow at UK winter temps with 40 strong enough for summer temps.
I think there's still a lot in our collective psyche that doesn't appreciate the science in modern multigrades, it defies our instinctive understanding of oils, fats and waxes, how can one oil be thin enough when cold and thick enough when hot? It's witchcraft! :)

I'm currently using Fuchs 15/50 in my V70R. Basic mineral and I change it <3000 miles. Doesn't use even a thimbleful between changes.

Mobil 1 5W50 will be absolutely fine in your C70. My old C70 was run on Mobil 1 0W/50 (it started life at that viscosity) then 5W50 when it changed, for its whole life (400k+ miles) from new.

I refer you to another thread currently active (98 V70R oil) which discusses oils to which I have posted fuller discussion and a link to a useful document about the technical aspects of oil.

Seemingly, the main reason semi-synthetics were produced was to give an oil of superior performance over straight mineral oils at a price to consumers who were resistant to the much higher cost of full synthetics. Once you get to grips with the chemistry of full synthetics it's pretty clear that semi-synthetics are just a cost issue.

Having said that, not all cars will benefit or tolerate full synthetics - I'm talking now of pre 1970's cars where issues may occur with oil seals although if replacement seals of modern materials have been fitted then this is no longer a problem. Also, very early gearbox in sump cars like the A-series engined Mini, Austin and Morris 1100/1300, etc, do better on mineral but later ones were factory recommended to use semi-synthetics.

Regards
John



Regards
John