just changed oil 5/30 full syn castrol A1 small print in handbook says use A3 as A1 could cause damage.

whats the difference?

Its the requirments of the emmision equipment. A1 is pretty much the old Ford spec (now replaced by A5). The oil will not damage your actual engine but it could damage parts associated with emmision control and result eventually in a fault light.

Would suggest you change to the correct spec.

A link to all you need to know. http://www.acea.be/images/uploads/files/2012_ACEA_Oil_Sequences.pdf

Edited by skidpan on 03/09/2013 at 17:18