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 investors' portfolios.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Janus Henderson Global Technology Institutional (JGLTX) has a 0.73% expense ratio and 0.64% management fee. JGLTX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. With yearly returns of 17.7% over the last five years, this fund clearly wins.

Federated MDT Stock Trust Service Class (FSTKX Quick QuoteFSTKX - Free Report) : 0.99% expense ratio and 0.65% management fee. FSTKX 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. FSTKX, with annual returns of 14.29% over the last five years, is a well-diversified fund with a long track record of success.

GMO-Usonian Japan Value Creation VI (GMAHX) is an attractive large-cap allocation. GMAHX is a Japan - Equity mutual fund investing primarily in companies based in Japan. The country remains somewhat exposed to global economic trends with its export focus, while its lack of natural resources also can impact the nation. GMAHX has an expense ratio of 0.6%, management fee of 0.56%, and annual returns of 12.38% 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.