If you have a completed and signed T2200 - Declaration of Conditions of Employment form from your employer, you can claim the entire cost of any motor vehicle expenses you have incurred. This includes fuel, insurance, maintenance & repairs. You will also need to have kept a log of the total kms driven in the year, and the kms driven for employment purposes. 

Here's the CRA guide for claiming employment expenses: https://www.canada.ca/en/revenue-agency/services/forms-publications/publications/t4044/employment-ex...