Almost 2 in 5 drivers are either not receiving any car insurance discounts (30 percent) or do not know whether they are receiving any discounts (9 percent), according to a new InsuranceQuotes.com report.

A common discount that most people are not aware of is a discount for receiving statements by email; only 33 percent of Americans with car insurance know about this discount.

Fewer than half (48 percent) know that their credit score can affect how much they pay for car insurance. Car insurance also costs less for married drivers; only 57 percent know that.

Young drivers are the least likely to receive discounts, which is unfortunate, since they already tend to pay the highest rates due to their inexperience and perceived risk. Only 34 percent of 18- to 29-year-old drivers say they are receiving at least one car insurance discount.

"There are dozens of possible discounts, and many are easy to qualify for," according to Laura Adams, senior insurance analyst with InsuranceQuotes.com. "Start by calling your insurance company, because you won’t automatically receive all the discounts you’re entitled to." That’s news to 39 percent of Americans who have car insurance, according to the InsuranceQuotes.com report.