Paypal is trustworthy. I suspect your buyer might not be.
Lots of scammers purport to be using paypal but are not.
Sell your car in person for cash. Very few legit buyers cant pay you that way.
Scammers use links that LOOK like paypal but are not.
Ask the person, WHY can you only pay with paypal ?
There is about a 3% fee for accepting paypal even if its legit.
So,for most big ticket items, sellers don't accept paypal for anything but a deposit or a small portion of the purchase price.
Bottom line is paypal is only as trustworthy as the other person. If he is a scammer, you could get scammed.
Now, I buy stuff off ebay all the time and pay via paypal. I use links on the actual ebay site to take me there so I know its legit.
Your guy contacted you via craigslist. He will probably want to pretend to pay you over & above your asking price without ever seeing the car and then ask you to send a check for the excess.
For example, your car is $3500, he sends you $6000 and tells you that you can keep an extra $500, just send him a $2000 check.
Oh and he never sees or comes after the car. He just keeps the $200 and his $6000 payment wasn't real or gets reversed.