Fully synthetic and Semi-synthetic oils.

Honest John Back Room » Motoring discussion
View Threaded
Mon 6 Jun 2005 12:13
Fully synthetic and Semi-synthetic oils. - Chad.R

A post on the technical matters forum got me wondering ...

Is a semi-synthetic oil at the top end of the quality spectrum (assuming there is such a thing), better* than a fully synthetic oil at the lower end, or is fully-synth oil ALWAYS going to be better than semi-synth?

I suppose in other words, is there an overlap in the quality spectrums of the two or not?

* I'm not sure quite how you'd define "better"(?) - but leave that up to you.
Reply | Report as offensive | Link
Mon 6 Jun 2005 14:21
Fully synthetic and Semi-synthetic oils. - Roger Jones
Depends partly on the age of your car, I suppose. Fully synthetic is unlikely to be the best for an older car that has always been lubricated with mineral oil.

As for overlaps in the quality spectrum, I guess that's distinctly possible, but I wonder whether any comparative evidence exists to prove it one way or the other.

That apart, I believe it is commonly thought that fully is better than semi is better than mineral. However, there is at least one school of thought that considers semi to be no better than mineral and therefore a waste of money. I was convinced by the arguments and evidence supporting that view, so I use mineral in my older cars (both have always been on mineral) and fully in the newer ones (both have been on fully since about 20k).

Chris Longhurst's Oil Bible is is a good place to start looking into these issues:

tinyurl.com/e3ei

And this one may offer a different perspective:

lubricants.s5.com/
Reply | Report as offensive | Link