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 break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

Century Small Cap Select Investor (CSMVX Quick QuoteCSMVX - Free Report) has a 1.25% expense ratio and 0.85% management fee. CSMVX is one of many Small Cap Growth mutual funds; these funds tend to create their portfolios around stocks with market capitalization of less than $2 billion. With yearly returns of 15.93% over the last five years, this fund clearly wins.

MFS Mass Investors Growth Stock B (MIGBX Quick QuoteMIGBX - Free Report) : 1.46% expense ratio and 0.33% management fee. MIGBX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. With yearly returns of 13.49% over the last five years, MIGBX is an effectively diversified fund with a long reputation of solidly positive performance.

Dreyfus Large Cap Equity I (DLQIX Quick QuoteDLQIX - Free Report) . Expense ratio: 0.77%. Management fee: 0.7%. Five year annual return: 10.72%. DLQIX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset.

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.