Hi, I'm trying to size up a suction line, for a positive displacement gear pump. I'm flowing 3.4 GPM. The oil I'm looking at using is Case IH Hy-tran. It has a SUS # of 208 at 100 degrees F and 47 at 210 degrees F. cSt of 40 at 40 degrees C and 6.3 at 100 degrees C. I have sized up a 7/8" I.D. suction line that gives me a velocity of about 1.8 ft/sec Reynolds number shows I have laminar flow. If the temperature drops to 0 degrees F or lower. I know it will take more horse power to move the oil. I also know about the tube I.D. ruffness. I'm worried about the pump cavitating on cold days until the fluid warms up. Will the lower temp cause my Reynolds's number to change? Will it change the velocity? If so, I would think a larger I.D. suction line is in order.... Is there a way to calculate the known SUS # or cSt # for the temp change? Or do I have to contact the oil manufacture and find this out? I have a feeling if the SUS and cSt is graphed by temp; it would be some kind of curve and not a straight line? I'm hoping someone can straighten me out on this and get me in the right direction. Thanks!