Canola Oil vs. Shortening For Pie Crusts

Can canola oil be used as a substitute for shortening or butter in pie crust recipes? 

We prepared our favorite pie crust recipe, which calls for both butter and vegetable shortening, using liquid canola oil in place of the solid shortening. Though the crust made with butter and oil got slightly darker than the crust made according to the recipe, it looked fine. When we broke into the crust, however, all was not fine. Whereas the butter and shortening crust was tender and flaky, the butter and oil crust was crisp and crumbly, not something we look for in a pie crust. Why the discrepancy? Shortening is a solid fat, so it can be worked into small bits that leave behind tiny spaces when they melt in the oven, creating flaky layers. The oil, of course, is already liquid and so leaves no spaces behind as it heats up. The result is a crisp texture, more like that of a cookie.