Using High Efficiency Detergent in a Regular Washer (need answer fast)?

Long story short, my SIL bought the wrong type of laundry detergent for our washing machines. She bought the kind designed for American high efficiency washing machines. I dumped some sheets into the machine and started the washer before noticing this. I turned the washer off just to be safe, but then started to wonder. What exactly could go wrong? I know regular detergent in a high efficiency machine will create too much suds and disturb the wash cyle, but does anybody know what the opposite (high efficiency detergent in a regular washing machine will do)? The machine in question is only a few years old.

HE detergents are formulated to work with less water and fewer suds. It should work just fine, and rinse a bit cleaner than your normal soap.

The main characteristic of HE detergents is very low sudsing. It will work fine in a regular washer.

You can use HE detergent in a topload washer without incident, and you can use regular detergent in a front loader, at least short term. Your clothes in the regular detergent/front loader combo might not have the suds wash out as well or come as clean. Long term use can mess up the pump used to drain the front loader tub, however.