After draining the oil from my 2920, complete with filter change, it was time to add a fresh new batch of 15W40. This is one of life's simple pleasures that I enjoy immensely. The owner's manual indicates, in accordance with common thinking, to add oil until it registers to the "full" notch on the dipstick. The manual also indicates that 3.7 quarts of oil should be used. I have added an entire gallon and the oil level registers only halfway between the "low" and "full" notches on the dipstick. Should I add more? Thanks!