I just changed my oil in 2018 Verado Pro. I put in the required amount of oil and it's still below the cross marks on the dipstick. I have tilted the motor and let sit for over a minute 3 times and have done everything the manual says. I bought 2 gallon of oil and I have about 1/2 quart left in the 2nd gallon. Do I leave it or keep adding oil??? I have pictures of where the oil is on dipstick but this site is so hard to upload pics.....also could there be a possibility the oil gallons could have not been all the way full to 4 quarts