75W-90 won't hurt it for short durations. I wouldn't go about driving high speed on the freeway for extended periods of time. You just want to get the water to go into suspension forming that foamy stuff so that it comes out. As soon as it is in solution, you want to get it out.


Water will reduce the oil's ability to lower friction. So... If you have been forcing it into gear, you might have done some permanent damage. Just change it out a couple times and see if it helps.