In heavy oil and bitumen reservoirs, oil viscosity is a vital piece of information that will have great bearing on the chosen EOR scheme and the recovery expected. Prediction of in situ viscosity with a logging tool would be very beneficial in reservoir characterization and exploitation design. Low field NMR is a technology that has shown great potential as a tool for characterizing hydrocarbon properties in heavy oil and bitumen reservoirs. An oil viscosity correlation has previously been developed that is capable of providing order of magnitude viscosity estimates for a wide range of oils taken from various fields in Alberta. This paper presents tuning procedures to improve the NMR predictions for different viscosity ranges, and extends the NMR viscosity model to in situ heavy oil in unconsolidated sands. The results of this work show that the NMR oil peak can be de-convoluted from the in situ signals of the oil and water, and the bulk viscosity correlation that was developed for bulk oils can be applied to predict the in situ oil viscosity. These results can be translated to an NMR logging tool algorithm, allowing for in situ measurements of oil viscosity at the proper reservoir conditions.