I have a 1981 Ford 302 V8, w/ 96000 original miles. Using dino oil, I can change the filter + oil, refill with 5 qt and its just a few cm's below the max fill line on the dipstick. Using the same filter and 5 qt of synthetic oil, the oil is right on the max fill line. This is checking after about 100 miles of driving and letting the oil drain down into the pan overnite. Why is there such a big difference?