The vehicle I'm changing oil in is a 2000 Jeep Wrangler Sport, 4.0L with 79,000 miles. I want to switch to synthetic oil, but the cost is pretty high. I went to Carquest to price oils, and I was told the Carquest brand is made by Valvoline and is the same as their line, but a lot cheaper. Is this true, or is it the stuff Valvoline rejects then sells to Napa or Carquest?