First things first... You shouldn't be paying cash for anything in the first place. Second, you need to call an accountant. You don't need the IRS breathing down your neck because you decided to claim something you "thought" was ok. Everything in this thread so far, is misconstrued from what the code really says. Call a finance company and do a sale/leaseback on the equipment, with a $1 buyout option. Then claim a deduction on any payments you make, as you make them, while having the cash to use now.
Mileage and weight limits are for mixed use vehicles... privately owned but sometimes used for business. Think "real estate agent". Also, do you know the ramifications of depreciating an assets value to the IRS? That means when you sell/trade it, you pay taxes on any value received/perceived thats over the depreciated value.
Now, I'm not an accountant, so call one of those... But be sure to learn about sale/leasebacks and how you can benefit from it.