In Answer to Question on Oil Weight?

The reason I know it was 10w30 was because it was on receipt. I had asked them to use High Mileage 50W because that is what I have used for two years now. And I am very good about getting the oil changed withing the time limit suggested. I have always taken very good care of my car. It is a 1992 Mercury GM and has been in excellent condition with only 121,000 miles. I know that is a lot of mileage, but not for that old of a car. Anyway, I told the car repair shop exactly what it was doing, shouldn't they have been able to tell it was something other than a radiator hose ? And would going from a high mileage 50W oil to a 10W30 oil cause it to overheat ?
In Answer to Question on Oil Weight?
actually using thicker oil than whats called for by your owners manual is killing your engine.I'm surprised you haven't replaced an oil pump yet,or you simply omitted to mention that. the oil helps a little bit in cooling but its primary job is lubrication.if the hose has developed a leak or is getting old it will drip fluid out of the cooling system,and will cause your car to overheat.how old are the hoses? if their original,the hoses may be doing whats called %26quot;sweating%26quot; and losing the coolant through evaporation,which would leave no sign of dripping,but would still lower the coolant level,and the cooling systems effectiveness.
In Answer to Question on Oil Weight?
the engine use the oil not only for lubrication but, also for cooling purposes



the oil pump force the oil through the gallery in the engine.with pressure and Speed. (the thicker the oil ,the higher the pressure and lower the speed)

high viscosity oil is producing(by not removing it) more heat

because, the oil gallery restrict the oil speed and also modern engine depend a lot in oil speed.

when the speed of the oil in the engine gallery is too slow then hot spots form in the engine sub secuently warpage might overcome and burned oil (might turn rock) start clogging the gallery.

unfortunated,the clogging always start forming in the most need it areas of lubrication.
1992 Mercury GM? No doubt your car was designed to run on either 5W30 or 10W30. Who told you to run 50W oil? 121000 miles isnt high mileage if you take care of it but running 50W oil isnt helping it any. If its over heating it is probably caused by something else like maybe a stuck thermostat.
your question starts out oil and ends up overheating. YOU NOW NEED TO GET GOOD MECHANICAL HELP. Switching from 20/50 oil to 10/30 oil will not cause overheating. Might make more motor noise on start up. Get the thermostat and radator tested. then procede to more expensive things. Some of the Ford engines have plastic intake manifolds that crack around where the thermostat and top hose hooks up. Good luck %26quot;CARNAK SEES NEW CAR IN YOUR FUTURE%26quot;
no it wouldn't make it over heat. summer time you run a heavier oil weight because the heat will break the viscosity of the oil and damage your engine. winter time you use a lighter weight oil because it will make it a lot harder on the battery and starter turning the engine over to start.