I have a '98 Oldsmobile Intrigue and after about 20 minutes of driving the temperature gauge is between one half and 3 quarters. I was wondering if is this a problem? The coolant is at the right level, and it looks brown. The car has almost 170k+ miles on it. Thank you for your time and any maintenance tips.
What stands out the most is that the coolant is brown. I have never heard of a coolant that is supposed to be brown. They are generally a yellowish green. It sounds like you need to replace the coolant, and then see where your gauge goes. For a specific car, without a specific temperature label, it's hard to know if that reading is too high or not. Perhaps if there is a red band on the gauge, if you're getting close, then it is too high.
As to how to change the fluid, first thing, look up what kind of coolant your car calls for. The Chilton's, or Hayne's manual will have that, as well as your owners manual. Get the right kind of coolant your car was designed for.
I don't know about your car in particular, but generally speaking, older cars have a drain valve / petcock on the bottom of the radiator. Put the car front end on jack stands (NOT just a floor jack, jack stands) and put a large bucket under the drain. With the engine cold, open the valve and let the coolant drain into the bucket. After it slows, remove the lower radiator hose to drain the remainder of the fluid. Once it stops, replace the hose, close the valve, and fill the radiator with the new fluid. Your manuals will tell you how much coolant your car needs.
One thing about about this. Your coolant is really dirty, and there will still be pockets of that nasty fluid inside the engine after you drain it this way. Hopefully one of our experts here can suggest a way to cycle that nasty fluid out so you only have to do this replacement once.
NOTE: That bad coolant is very poisonous to pets and animals. It's also very sweet so it tends to be irresistible to them. It should be bottled and taken to a recycling facility for proper disposal. You can even pour it into the jug you bought the new fluid in.