There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

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.

Davis Appreciation & Income Y (DCSYX): 0.68% expense ratio and 0.55% management fee. DCSYX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual. With annual returns of 10.97% over the last five years, this fund is a winner.

Northern Large Cap Value (NOLVX): 0.57% expense ratio and 0.53% management fee. NOLVX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. NOLVX, with annual returns of 10.76% over the last five years, is a well-diversified fund with a long track record of success.

TIAA-CREF Growth & Income Retail (TIIRX) is an attractive large-cap allocation. TIIRX 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. TIIRX has an expense ratio of 0.67%, management fee of 0.4%, and annual returns of 15.07% 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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