Best method to detect oil density: Which technology does the oil industry use for inline, oil density measurements?
There are a number of methods. The newest and probably one of the most frequently used nowadays is Coriolis, but you can also use the old-fashioned method of having a slug catcher or other vessel fill to a certain level measured via level switches, then use a DP cell to measure the liquid pressure, which due to the fixed height is equivalent to the density. This is the old-fashioned knock system.
There also are ultrasonic and level sensor applications, so the big issue is to decide where the measurement will be taken, the complexity of the equipment and/or accuracy required.
I'm sure there are several analyzers that are specifically designed to provide very detailed oil component analysis. However, if all you need to measure is density, then I suggest a Coriolis meter, which gives you density, temperature and flow in one meter. It is reliable and can be very accurate if the proper manufacturer/model is selected. If the line is large, you can save money by placing a much smaller-sized meter on a small recycle stream.