Low salinity water flooding is a technique where, by injecting reduced salinity seawater, oil recovery can be significantly improved in some sandstone reservoirs. It has been generally agreed upon that this works predominantly by improving the water wettability of the reservoir rock. However, the mechanisms that underlie this salinity-induced water wettability alteration are still poorly understood, largely because of the high degree of complexity of these reservoir systems. This is found in the variety of the oil, brine, and mineral phase contents; in the multi-scale porous system, and in the high temperatures and pressures involved. In designing an experiment to find the underlying wettability mechanisms one must therefore either include a high degree of complexity to get realistic, but difficult to interpret results, or greatly simplify the system to gain insight into very specific mechanisms, which are however not guaranteed to be relevant under more realistic conditions. A wealth of literature exists largely on the more complex side of these experiments, and, since recently, much has been done using highly simplified systems. In this work, I aimed to bridge some of the mechanistic insights gained from simplified systems with the current knowledge of low salinity water flooding at realistic conditions. Therefore, I opted to look into systems of low-to-intermediate complexity. This work is set-up such that each chapter adds a degree of complexity, starting with single-salt brine/oil/mineral systems at room temperature, and ending with complex multi-component brine/crude oil/oil-aged mineral systems at elevated temperatures. The general form of these experiments has been kept constant: a single droplet of either oil (n-decane with fatty acids, or crude oil) or brine, in an ambient phase of the other kind, deposited onto a mineral substrate, usually mica. I measured the wettability response of the systems by registering the contact angles of the droplets, and how these depend on the conditions of the system. In some cases I also looked into the physico-chemical properties of the substrates, to study the underlying mechanisms in further detail.