You don't need to invest in anything other than an emergency fund and your work retirement plan. There is absolutely no need to dabble in the stock market when you have a 10 year 6% and 5 year x% loan outstanding. You'll be spinning your financial wheels and more than likely rolling backwards.
1)Sell your car and buy a beater that gets the job done. Use cash if possible.
2)Continue to get the 401(k) match.
3)Put $100 in a separate bank account every month for an emergency (use direct deposit if your company does that).
4)Come up with a reasonable plan to pay your student loans off as quickly as possible.
5)Bank whatever else you can .
You can't see it, but I'm playing my heart cries for you on the worlds tiniest violin as I type this.
No one made you take those loans out. No one.
This is ridiculous. You're an engineer if memory serves. I'd guess $50-$55K at least. Your stoner friends probably make $15K a year at said gas station. Get some perspective man...
Why do you care what other people think?
Great, another defaulted loan I can help pay for. Are you going to give your degree back?
IMHO this is a terrible idea and it's a terrible idea because you are thinking too small. Life does not exist in a bubble. The gains you make in the stock market (less trading prices, commission, etc...) have to be greater than the savings you would achieve by paying off your debt.
Why don't you get a part time job and put every penny of that income into your student loans?