From the 2019 parts pictures (see previous posts), the non-fan-assisted oil cooler looks different from the assisted one (at least the mounting point areas). Maybe you can buy the fan and fan holder and install it on the oil cooler but you will have to cut the oil cooler mounting points. I guess someone can try but, after time spent, I am not sure there will be any savings.
Again, from the parts pictures, the 2018 oil cooler assembly seems to have the fan bracket, minus the fan. I am guessing that Harley decided to reduce production costs (but increase inventory costs). So, it may be possible for one to get the 2018 oil cooler assembly and add the fan to it.
I use the dip stick oil temp gauge to monitor temps.
Again, anything that can potentially lower oil temps on a Harley, is a good upgrade, as far I am concerned.
