Whats the difference in oils?

I have heard that occasionally from people in the past.... and asked them to explain why that would be so. Nobody has EVER explained successfully how to back up that arguement.
IMHO, how can an oil which is better in every respect, be bad for older engines, assuming one DOES get the correct viscosity.......? Perhaps if your engine was full of sludge and dirt it might block the filter quickly, but you can always do your first oil filter change early after going synthetic if that's a concern.
If possible, cut your filter open and see what's in it when you change the filter- very easy with a paper cartridge but a lot more difficult with the spin-on variety. (On aircraft engines it is mandatory to look at the oil filter every time it's changed.)

Now I even run my 20 yr old Briggs and Stratton mower on Mobil 1 or the equivalent Shell synthetic! (Depends on what I have in the garage at the time...)
Cheers

I beg to differ. I had an old holden 308 rebuilt by a GOOD engine shop and was told specificly NOT to use the modern oils including synthetics because he had seen cases of the rubber oil seals and valve stem seals break down because of the addatives used. Also you need to watch the viscosity levels as a lot of the synthetics are thinner and in an old engine you can have oil preasure problems. Another thing I have been told many times is what ever brand of oil you use, stick with it or do a proper engine flush because different manufactures use different formulas in the base oil and the're not always compatable.
Just my two bobs worth...

that 4 x 5L of a mineral oil. I knew what I meant

Any other Rangie owners out there?
Check this....

http://www.britishpacific.com/rr/FAQ_synthetics.html

basically says superior but at a cost which seems to be the concencus here.