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.

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

Fidelity Small Cap Stock Fund (FSLCX Quick QuoteFSLCX - Free Report) : 0.73% expense ratio and 0.58% management fee. FSLCX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. FSLCX has achieved five-year annual returns of an astounding 7.18%.

Goldman Sachs Small Cap Value Insights I (GSITX Quick QuoteGSITX - Free Report) . Expense ratio: 0.85%. Management fee: 0.8%. GSITX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. This fund has managed to produce a robust 8.11% over the last five years.

JPMorgan Intrepid Value Fund R6 (JIVMX Quick QuoteJIVMX - Free Report) : 0.34% expense ratio and 0.3% management fee. JIVMX 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. With a five-year annual return of 9.93%, 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.