1 mol per mol to about 5 mol per mol sulfonic acid of water and about 1 mol per mol to about 10 mol per mol sulfonic acid of calcium hydroxide to form the reaction mixture the reaction mixture is heated with stirring to a temperature of from about 40 u00b0 c to about 200 u00b0 c preferably from about 80 u00b0 c to about 120 u00b0 c the mixture is preferably stirred for a period of time up to about 60 minutes more preferably up to about 30 minutes the resulting mixture is then separated to remove excess calcium hydroxide and any salts formed from residual sludge or so 2 one method of separating the mixture is centrifugation centrifugation should be performed for a sufficient amount of time to remove the excess calcium hydroxide and any salts this period of time can be any such sufficient amount of time for example 20 minutes the presence of the solvent greatly improves the speed of separation the solvent is recovered from the clear centrate for recycle by any convenient means such as a solvent stripper the product may be further concentrated via distillation or vacuum flashing to remove a portion or all of the unreacted oil this process may be operated in a continuous fashion in a manner such as that shown in fig1 sulfonic acid 1 is added to a reactor 7 followed by water 3 and lime 5 the resultant mixture then undergoes separation 9 with the lime and water being removed the next step is solvent recovery 11 followed by concentration 13 to produce the calcium sulfonate in base oil 15 the following examples are meant to further illustrate the invention without.