how many miles were on your DI when you made the change to Synthetic Spike???
When I bought my truck in April '07 it had 152,and change. My first oil change I used Castrol HD 30.
At 155,000 I switched to Mobil 1 15w-50 and I change it every 5,000 miles.
I now have 176,and large change.
After I first switched to full syn it leaked, I was adding a quart of oil every 1,000-1,500 miles. It gradually got longer and longer between adding oil.
Now I go a full 5,000 miles with out being any more than a half quart low.
I use Mopar, NAPA and Purolator oil filters.