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.

Columbia Balanced Z

(CBALX) has a 0.68% expense ratio and 0.57% management fee. CBALX is an Allocation Balanced mutual fund. Allocation Balanced funds look to invest across asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual; these funds are mostly categorized by their respective asset allocation. With yearly returns of 10.71% over the last five years, this fund clearly wins.

American Funds Mutual Fund R6

(RMFGX): 0.27% expense ratio and 0.23% management fee. RMFGX is a Large Cap Value fund. These funds invest in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. With yearly returns of 11.48% over the last five years, RMFGX is an effectively diversified fund with a long reputation of solidly positive performance.

Emerald Growth Fund Institutional

(FGROX) is an attractive large-cap allocation. FGROX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets. FGROX has an expense ratio of 0.79%, management fee of 0.61%, and annual returns of 11.12% over the past five years.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.

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