Online interactive systems offer the beguiling prospect of an improved environment for learning at minimum extra cost. We have developed online interactive tutorials that adapt the learning environment to the current learning status of each individual student. These Adaptive Tutorials (ATs) modify the tasks given to each student according to their previous responses. Feedback, assessment and remediation are also adapted. Over a three-year period we progressively blended ATs into notoriously challenging courses in introductory Engineering Mechanics. We assessed the impact of this initiative by reviewing three lines of data: (i) the built-in diagnostics of the system, (ii) changes in student grades from year-to-year and (iii) supplementary surveys. Generally, students liked the new blended system and grades improved. Detailed analysis revealed nuances in the measures of student learning, such as differences between high-performing and low-performing students. With these insights we are able to further adapt the system to meet the learning needs of our students.