I think you are saying that the bypass would be flowing only a fraction of the flow going through the cooler? So in effect, the bypass would be flowing 10% of the flow through the cooler, which is 10% of all flow when the bypass is active, which would be 1%. It makes sense, but an unhappy accident I had awhile ago suggested the bypass filter flowed close to a half a gallon per minute even when the cold weather bypass was active. I think when the engine is operating under highway conditions, that the filter is flowing significantly more of the total flow.Hydraulically speaking, since the bypass filtration is on the outlet end of the oil cooler, then the same pressure drop that causes the oil to bypass the oil cooler would also govern the oil flow to the bypass filtration. So in effect, the T-junction already exists.
If this is the case, I think it would have an impact on the temperature of the crank case. I'd also be concerned about if any damages could occur from the cold oil streaming into the hot valve cover could cause.
Regardless, the bypass filters are expensive, and so is the engine. I'd like to be sure the filter is flowing as much as it can all the time. If the pressure drop from oil routing around the cooler means the filter isn't flowing fully all the time, then I feel I'm not getting my monies worth out of the filter. I'd rather have the filter drawing as much warm oil as possible from the flow at all times. This is why I think having a T-junction after the t-stat would be better for those running the cold weather kit than the current bypass filter setup is that draws oil from the cooler.
I did something similar the night before I completely covered the grille. I only used a cereal box though. XD They had the same effects on the overall oil temp (had about a 7f increase over established EOT with a partially blocked cooler). If you'd like, I could redo the 50% block of just the cooler with cardboard wrapped in a plastic bag. Might be more airtight.I was hoping for a more direct application of the High Speed Fiber Based Structural Thermal Insulating Material (HSFBSTIM). If you could place the HSFBSTIM directly in front of the oil cooler, as in between the condenser and the oil cooler, it would give us more accurate cause and effect numbers.
Just saying, adding and removing a cover from the oil cooler is a much more painstaking process than from the grille... Particularly if it's something I'm going to do and undo every time I tow a trailer or everything the temperature spikes above freezing for a few days.