Originally Posted by Miller88
There's a few reasons why it's able to go 7500-10k miles. First is, it has a larger oil capacity per liter of engine than my Jeep. It's oil capacity is 5 quarts, my Jeep's is 6 ... it has half the engine displacement.
As a side note... If you're not already using a larger filter for higher capacity on your 4.0, you can use the filter for Ford small blocks. It cross-references to Motorcraft FL-1A. It looks like you might already be doing this since you mention 6 quarts, but I thought it was worth a mention...