CHEVROLET ASTRO ENGINE BURNING OIL

I Have Got A 1991 Chevy Astro Van. 196 Thousand Miles. A 4.3 Liter. I Have A Problem With Oil Burning. I Have Looked And Found No Leaks....

1997 Chevy Astro Van Mileage: 60,000. My Van Is Equipped With A Trailer Towing Package, 410 Rear End Etc. When Towing I Burn A Quart Of Oil...

2000 Chevy Astro On The Oil Stick In My Van It Says To Use 0 W 30 As The Oil I Have Never Heard Of This And The Auto Store Tells Me...