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.

Diamond Hill Select I (DHLTX Quick QuoteDHLTX - Free Report) : 0.87% expense ratio and 0.7% management fee. DHLTX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value. With annual returns of 14.63% over the last five years, this fund is a winner.

Invesco Small Cap Value Y (VSMIX Quick QuoteVSMIX - Free Report) : 0.86% expense ratio and 0.64% management fee. VSMIX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. VSMIX, with annual returns of 18.83% over the last five years, is a well-diversified fund with a long track record of success.

DFA Global Equity I (DGEIX Quick QuoteDGEIX - Free Report) : 0.25% expense ratio and 0.2% management fee. DGEIX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations. With a five-year annual return of 11.44%, 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.