My E430 capacity is 8.5 quarts but I filled with 8 quarts without any top off, OCI is 12-13k miles so the per miles oil usage is 0.00067 qt. 12000/8 = 1500 miles per quart, with this distance of 1500 miles it uses 68 gallons of gas. Cost of gasoline is about 50 times the cost of oil.
The LS400 capacity is 5 quarts, 1 quart for top off and OCI is 12-14k miles, per miles usage is 0.00050 qt.
S2000 OCI is 6k miles with 5 quarts and no top off, usage is 0.0010 qt per miles.