Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

How can you tell a good mutual fund from a bad one? It's pretty basic: if the fund is diversified, has low fees, and shows strong performance, it's a keeper. Of course, there's a wide range, but using the Zacks Mutual Fund Rank, we've found three mutual funds that would be great additions to any long-term retirement investors' portfolios.

Let's take a look at some of our top-ranked mutual funds with the lowest fees.

Davenport Small Cap Focus Fund (DSCPX Quick QuoteDSCPX - Free Report) : 0.88% expense ratio and 0.75% management fee. DSCPX is a Small Cap Blend mutual fund that usually targets companies with a market capitalization of less than $2 billion. With annual returns of 11.57% over the last five years, this fund is a winner.

BlackRock Impact US Equity Instl (BIRIX Quick QuoteBIRIX - Free Report) : 0.48% expense ratio and 0.4% management fee. BIRIX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. BIRIX, with annual returns of 11.84% over the last five years, is a well-diversified fund with a long track record of success.

Glenmede Large Cap Growth Fund (GTLLX Quick QuoteGTLLX - Free Report) : 0.85% expense ratio and 0.55% management fee. GTLLX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. With a five-year annual return of 12.71%, this fund is a well-diversified fund with a long track record of success.

There you have it. If your financial advisor had you put your money into any of our top-ranked funds, then they've got you covered. If not, you may need to talk.