I use Delvac MX 15W40 in my IDI and Powerstroke. The IDI did consume some oil too before that (whatever the preowner used?) and after I changed to Delvac no oil needed to be added between oil changes. Same with the Powerstroke which is do for an oil change now (almost 5000mls reached).
What is the mx? I got Delvac 1300 Super 15w40.