I have a 1997 Dodge Caravan with 149000 miles on a 3.0 engine. The rear seal is leaking about one qt in 1000 miles. I'm using 10w30 oil. Should I go to 40w oil?

 

You may want to remove the trans and replace the rear main seal. It is a one piece seal.

 

I have a 1997 3.0 van with 180000 miles as well, it also leaks somewhere, butI don't know where it leaks yet. Anyway, I just took a auto class not long ago and was taught that for older cars like mine and yours, the thicker grade should be used because there are more rooms between the parts inside the cylinders. So 10w40 is the way to go.I used 10w30 last summer, this winterI am using 5w30.I will try to use 10w30 in winter and 10w40 in summer whenI can. Good luckswitching the grade.

 

One thing to add: if you are using conventional motor oil, keep on using conventionals. if you are using synthetic oil, then keep on using
synthetics. Switching from conventionals to synthetics or the other way around on high mileage cars could break down the car because your car at such an age is already used to the type of oil being used. So the bottom line is switching grade in the same type of oils.
Good luck switching grades.