What "consumables" are we talking about? Just curious, since oil, oil filter, air filter, tires, brake linings, ATF, are all cheaper on the Civic.
Sure, this was never rocket science for me. Add up two columns/ miles= cost per mile driven: major tune. To help to normalize the costs, (aka like miles) the major tune mileages of 110,000/120,000 and 100,000 miles were used.
The whole Civic 110,000/120,000 service plus front rotors and brake pads cost 947. I would have delayed the interval if not for the the squeak from the brakes telling my wife there might be an issue. Like miles for the Jetta was far less @ app 650 (brake pads and rotors not needed). The math indicates .00789/008609 vs .0065 cents per mile. aka 21% to 32.4% ... more. Pads for the Jetta TDI (same commute, same drivers) pads and rotors swaged to go to a min of 250,000 miles @ 178,000 miles.
Oil and filter are done on 20,000 miles OCI's (vs 30,000 miles on Jetta TDI). I would have no issues running 30,000 miles OCI's, but the oil filter is not specified to run 30,000 miles like the oem VW filters and the Civic uses oil far more than the Jetta TDI, so it is easier to change oil at 20,000 miles rather than add oil and change again @ 30,000 miles. Air filters on 2x factory recommendations, oem tires got 74,300 miles (112,300 on Jetta TDI) brake pads and rotors only 120,000 miles, rear drums and shoes est to go 260k, ATF is 120,000/90,000 vs life in TDI/5 speed trans. TB/WP change, valve adjustment and gaskets changes etc 110,000 miles, spark plug and timing. All these things, you as an auto mechanic know about. So this is not rocket science for you either I suspect.
I personally was surprised at how much longer the valve adjust and timing belt and water pump change took over the TDI's.