Can I list my vechiles as an expense and an asset?

No. You're right. Vehicles are assets, but after reading this answer, you may want to delete those vehicles you entered as assets. If you have any other details regarding this question, please feel free to post them in the comment section. 

You may be referring to the Actual Expenses method of deducting your car for work. It is based on the expenses you actually incur in the operation of your vehicle. It includes things like:

·         gas purchases

·         repairs

·         oil changes

·         tire purchases

·         car washes

·         insurance

·         and even vehicle depreciation

However, you can only claim the percentage of expenses that apply to the business use of your vehicle. To compute this, you must know how many miles you drove for business purposes and how much you drove for personal reasons.

TurboTax will walk your through this method.

You can deduct 53.5 cents per mile or actual vehicle expenses (ie. gasoline. oil, tires, maintenance) prorated for business miles.

If you claim the standard mileage rate in year one for this vehicle, you will have the option of deducting the standard rate or actual expenses in subsequent years. If you claim actual vehicle expenses in year one, you must choose actual expenses in every subsequent year for that auto.

TurboTax will walk your through this method.

To enter your vehicle mileage for your business follow these steps:

While inside the software and working on your return, type Schedule C in the Search at the top of the screen (you may see a magnifying glass there).  There will be a popup that says Jump to Schedule C.  Select that to get to the general area. 

·         Click to Edit next to the business

.       Under Business Expenses click Start/Update on Business Vehicle Expense.

.       This is the Vehicle Summary Screen.

·         Follow along the interview and select Actual Expenses