What can cause your oil to be milky on 1999 Pontiac Montana

During oil changes the oil looks milky and the temperature gadge keeps running up. The temperature goes up and then goes back up. Then if you drive it ,it runs sluggish.

Asked by for the 1999 Pontiac Montana
G.M. claim to fame the pontiac montana. the lower intake mainfold is actualy part of the cylinder heads. when you change in intake gasket you actualy have to remove the valve covers to do this. water runs threw the intake manifold and if the gasket leaks water will get into the engine oil. loss of coolent under pressure will cause the engine tempature guage to go up. normaly the customers will think the headgasket is leaking or cracked but G.M. has numerous updated gaskets for the intake manifold, i believe it changes part numbers 5 or 6 times. ya for dex-cool
2 more answers
a blown head gasget
manifold or head gaskets can cause the milky resadue