A process for the production of a lubricating oil additive concentrate comprises reacting at elevated temperature the following components:component (A) a defined acidcomponent (B)--a calcium base added either in a single addition or in a plurality of additions at intermediate points during the reaction,component (C)--at least one compound which is (i) water, (ii) a polyhydric alcohol having 2 to 4 carbon atoms, (iii) a di- (C.sub.3 or C.sub.4) glycol, (iv) a tri-(C.sub.2 -C.sub.4) glycol, (v) a mono- or poly-alkylene glycol alkyl ether of the formula (I)R(OR.sup.1).sub.x OR.sup.2 (I) wherein R is a C.sub.1 to C.sub.6 alkyl group, R.sup.1 is an alkylene group, R.sup.2 is hydrogen or a C.sub.1 to C.sub.6 alkyl group and x is an integer from 1 to 6, (vi) a C.sub.1 to C.sub.20 monohydric alcohol, (vii) a C.sub.1 to C.sub.20 ketone, (viii) a C.sub.1 to C.sub.10 carboxylic acid ester, or (ix) a C.sub.1 to C.sub.20 ether, optionally,component (D)--a lubricating oil,component (E)--carbon dioxide added subsequent to the, or each, addition of component (B), andcomponent (F)--a compound of formula IIR.sup.3 X (II) wherein X is a halogen and R.sup.3 is an alkyl, alkenyl or alkaryl group or halo derivative thereof.