Fully synthetic oils are a COMPLETE WASTE OF MONEY!!!
Use tractor universal oil at about or under £1 a litre, and change it every 5/6000 miles.
My Disco TD5 has been running on that for 50,000 miles, and the last change was after 11,000 miles. The guy watching the oil coming out said it was so clean why was I changing it?!
My SAAB 900 Turbo is on over 100,000 miles on that same oil.
I use Brett Oils OVOLINE Tractor Universal and I buy a 210 litre barrel and get a good price.
The secret with oils - keep it clean, keep it HOT, and change it when it gets dirty or wet.
Remember, Fully synthetic is NOT a better lubricant, but it does last longer. At £1 a litre for TU oils my changes cost me £6 or so. Compared to the price of Fully synthetic that's not a lot. For the same money I could change my oil every 500 miles, never mind 5,000!
We have had this discussion before, and remember, garages and oil companies make BIG profits on forecourt oil sales.
CharlesY