I have a '95 Grand Caravan, at present 115,000 miles, but of those miles, only about 1300 miles have been put on since January '04. I have done annual oil changes since then, regardless of the miles for the year, and usually the change is done in early April. It has seen nothing but M1 5W-30 since summer '98, but this last change (over the weekend, I was a little late this year) I didn't have any 5W-30, so I decided to use up my random quarts.
In went:
1 qt M1 TSUV 5W-40
1 qt M1 0W-40
1 qt M1 0W-30
1 qt M1 0W-20
1 qt Syntec 0W-30 (made in USA stuff)
It's not that I don't care about this car anymore, well, yes it is. Other than gas and oil, this car will get no other maintenance. It's better than 50/50 that we'll get rid of it by the end of summer. The mixture appears to be a little more viscous than it's used to, but as long as it turns over and starts once every two or three months, I'm good.