Should I donate my car or should I junk it?

My 91 honda accord would not start up nor would the key shift when placed in the ignition. My mechanic was able to start it up but told me that my key lock cylinder needed to be replaced and that it would cost about 800 to fix. I don't think its worth it to fix so I'm wondering if it would be more beneficial to just pay the mechanic fees ($120 for diagnosis and getting the car to start), donate it fof a tax deduction (which means I'm out $120 from the get go, but get some kind of tax deduction) or if I should give it to a junk yard offering me $120 (meaning I would "break even").

Most likely junking it to break even is your best option.

A tax deduction for a charity donation only works if you have enough other items to meet the requirements for itemizing your deductions. Also, you need to donate it to the right kind of charity. Not all charities are recognized by the government for itemizing large donations. Donating a car of that age will hardly be enough to qualify for itemizing unless you also have other qualifying deductions to make your total itemized list higher than your standard deduction.

The next issue is that most charity organizations that accept donated vehicles expect the vehicle to be in working order. Your vehicle is not.

Junk it. A tax deduction won't be worth that much, and may very likely be worth nothing.

There are a couple organizations in my area that accept broken down cars.

I will be filing single and have made hundreds of dollara worth in donations to goodwill

Junk it.

You won't get ANY benefit from a donation unless you itemize deductions on your return. And with the standard deduction for a single filer going from $6,350 in 2017 to $12,000 in 2018, it's even harder for many people to benefit from donations.

Even if it would benefit you, you wouldn't benefit that much. You can no longer take 'book' value. You may only take what the charity gets for it. They give you a receipt after they dispose of it, showing the actual cash value they realized. If it's something they can't sell without needing work, they will sell it to a scrapyard. You'll get the value of that as a deduction… Meaning that if you can deduct it, you would pay tax on $120 less of income. If you're in the 12% bracket in 2018 (down from 15% in 2017), you'll save about $15 in tax.

You are much better off, if money in your pocket is what matters, selling it to the scrapyard yourself.

For tax purposes, you can ONLY claim a deduction for the amount the charity actually gets by SELLING the car, or the 'blue book' value if that ACTUALLY USE the car. If the car isn't worth fixing, and won't run without fixing, you will come out ahead selling it to a scrap yard.

Note: The tax benefit of donating NEVER equals the value of the item donated. Unless you would have donated the item anyway, you CAN't financially benefit by donating it and claiming a tax deduction.