Just wondering what they are (except price)and why not all manufactures recommend it for their cars - including Subaru!?
I was told by a Porsche mechanic that it isn't worth the extra cost over semi synthetic oil and he said something about deposits building up to the detriment of the engine... Anyone shed any light on this?

 

Dont Porsche reccommend a fully synthetic for their cars anyway? (Mobil 1 springs to mind )

Tony

 

Subaru have no problem with you using fully synth provided it is the correct grade.

They recommend a semi synth as it is half the price and this keeps running cost figures lower.

 

Thanks, I guess calling him a Porsche mechanic wasn't technically correct. He's a mechanic at an independant Porsche specialist...
So, there are absolutely no downsides to fully synthetic oil and it is better than semi in every way and worth every extra penny (in your opinions)?

 

Yup better in all aspects (except price )

Tony

 

Can only guess what he meant : If you use a mineral oil for a long period it tends to build up deposits. If you move to a fully synthetic oil it breaks down these deposits, some of which may be serving a useful purpose in blocking holes, etc. These deposits would then also clog up the filter. Lay mans understanding this.