The third type of primary additives consists of groups of formulae 2, 4, and 7, in which each of R2, R9, and R10 independently is an alkyl group containing from 1 to 3 carbon atoms; R24 is an alkyl group containing from 1 to 4 carbon atoms; c is in the range of from 0 to about 50; x is 0; y is in the range of from about 5 to about 25; and z is in the range of from about 0 to about 25.