Changing the oil was the most frustrating thing to figure out when I got my 2007 2350. I've always changed the oil in it and I've never had anybody else to do it. The first time I changed the oil, I had read it took 7 quarts which is what I put in it. Checking the oil level showed too much oil and then I read about all the problems Ford had with the markings on the oil dipsticks being incorrect. So I was left wondering if showing too much oil on the dipstick was really correct or if the dipstick marks were incorrect.
Checking the owner's manual said it should only take 6 quarts. So the next time I changed the oil, I put in 6 quarts and it was halfway between the oil marks. So once again, I was confused and since the owner's manual didn't specify if the 6 quarts was with or without the filter change, I added about 3/4 quart more to get to the upper mark. That was until I realized it takes a lot longer than I was used to for the oil to drain out of the engine back into the oil pan after running the engine. I thought I had the correct amount of oil, but when I checked it 5 minutes later, it was showing too much and I had to remove some.
Assuming my oil dipstick is correct, it appears that it takes just a little over 6.5 quarts of oil which I'm assuming is for the filter for the oil level to reach the upper mark on the dipstick. Of course it was still in the back of my mind that the dipstick markings could be incorrect. Plus, I know that too much oil is not good either. I finally gave up trying to figure it out and I just assumed the oil dipstick was correct and I ended up using 6 quarts like the owner's manual said. This was also my first vehicle with a Ford engine so I thought maybe the oil reading should be in the middle of the oil dipstick marks and not all the way up to the upper line like it is on GM engines.
I now have almost 50,000 miles on my RV and the engine still doesn't burn enough oil to get down to the bottom oil mark on the dipstick before the next oil change. I've also use the Motorocraft 5W-20 oil and filter that I get at Walmart. I buy one 5 quart jug and 1 quart bottle of oil and the filter. Plus, I usually try to change the oil every 3,000 and I grease the chassis at the same time. It takes a lot less time for me to do it then to take it somewhere to have this done. Also, with my previous RVs, I have sent oil samples to Blackstone Labs to have the oil analyzed. From past experience I know oil usually won't last 5,000 miles before it doesn't protect the engine as well even using Mobile 1 synthetic oil. So I stick with the 3,000 mile interval between oil changes.
