Engine oil contains 1 - 10 nm calcium carbonate particles stabilised with a surfactant. One commonly used surfactant headgroup is salicylate and we have shown that in the presence of moisture these surfactants are stripped from the particle surface, resulting in aggregation. We have observed that when using a magnesum cation for the salicylate headgroup the resulting dispersion gels, in the presence of moisture. We wish to understand this process.We have shown that the salicylate surfactant in organic solvent forms a number of different morphologies dependent on the cation and we hypothesise that these different shapes result in differing depletion interaction and hence differing dispersion behaviour. Using SANS we will determine the particle structure in the gel and also investigate the dynamics of formation. Combined with rheological data this work will show the range and magnitude of the attractive potential leading to gelation.