How's this for a plan. Start out with a 50/50 mix of HM/regular dino. Run it 3k and change to full HM dino. After that go with synthetic HM (hopefully) for many years to come. I've had leaks start from switching to synthetic in high mileage engines in the past, so I'm a little shy about making the change right away. But I am convinced that synthetics are worth the extra money, and do want to go in that direction. I put HM synthetic in my 97 Chevy van with 120K last fall, and it started some leaks. I'm back to HM dino with that one.