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.

Putnam Multi-Cap Growth Fund B (PNOBX Quick QuotePNOBX - Free Report) has a 0.8% expense ratio and 0.5% management fee. PNOBX is an All Cap Growth mutual fund. In order to increase diversification, these funds have holdings across small, medium, and large-cap levels. With yearly returns of 12.16% over the last five years, this fund clearly wins.

Fidelity Advisor Equity Growth I (EQPGX Quick QuoteEQPGX - Free Report) : 0.71% expense ratio and 0.52% management fee. EQPGX 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. EQPGX, with annual returns of 17.18% over the last five years, is a well-diversified fund with a long track record of success.

JPMorgan Intrepid Advantage Fund A (JICAX Quick QuoteJICAX - Free Report) : 0.64% expense ratio and 0.3% management fee. JICAX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 12.77% over the last five years.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.