MG Car Repair: oil cooler, viscosity index, oil coolers

Question
Howard, I recently bought a 1970 mgb. After repairing a number of minor things to make it road worthy I noticed that a previous owner has a piece of outdoor carpet wraped neatly around the oil cooler connected with a piece of wire. It appears to have been there for some time. I took it off to examine the cooler and it seems to be in perfect shape. My question is should I leave it there or remove it. I will only be driving the car in warm weather so can't see the purpose. Oil pressure of the car is fine. Thanks for your help in advance.       Terry

Answer
Hi Terry,
Part of the cooling of any engine is done by the oil itself, so keeping the oil cooler is necessary as heat is something that accumulates and needs to be removed when it gets too high. In cold areas in the winter it becomes a problem when you can't get the oil warmed up so some people block off parts of their radiators and oil coolers. (thus a wrapped up oil cooler) There are oil cooler thermostats now available in the aftermarket to bypass the oil cooler in cold conditions to raise the oil temperature and automatically open the flow to the cooler in warm conditions to cool the oil down. If you only drive the car in warm weather, you should leave the oil cooler on and  open to fresh air and leave the carpet off of the cooler.

Cold oil does not circulate well in tight places and that is why they covered the cooler. Over heated oil tends to loose it's viscosity (gets too thin) depending on it's "Viscosity Index". (the ability of a oil to maintain it's viscosity when heated) So a covered oil cooler in warm weather  under hard circumstances, can over heat the oil and do harm also. Since you only intend to use the car in warm weather you should just remove the carpet and leave it off. If you have to drive it in very cold weather just stick a piece of cardboard in front of the cooler for the cold weather running and put the cardboard in the trunk when it warms up.

Howard