03 GTP. Bought the car last July. DIC Oil Life calc was at 98%, oil filter looked new, so I assumed oil was new. I drove between 4k and 4.5k before Oil Life calculator got to 0%.
I change oil and filter w/ Fram filter and Castrol convention oil that was 50% recycled, reset DIC calc. Oil Life calc dropped to 97% at 100mi. Project that math out, and it would reach 0% at 3,333mi. That's significantly less than when I bought it.
Then a piece of plastic from my dipstick brooke in the tube/pan. So I drained oil and changed filter, in a fruitless effort to recover plastic pieces.
This time I used Penzoil conventional oil with a CarQuest filter (b/c it was on sale). A week later, road trip for holiday weekend with beautiful weather and wide open freeways. I monitered my guages. 1,100 miles, 3/4 of time had cc set 78-80.
This time the DIC Oil Life calculator hit 90% at 1,270miles after Penzoil conventional/Carquest filter. Project that math out and its 12,700 miles before oil life calculator would hit 0%!
Now that's a big differnece. What gives?