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.

If you are looking to diversify your portfolio, consider Sterling Capital Behavioral Small Value I (SPSCX). SPSCX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. This fund is a winner, boasting an expense ratio of 0.89%, management fee of 0.6%, and a five-year annualized return track record of 10.37%.

American Funds Investor Company of America R5 (RICFX): 0.31% expense ratio and 0.23% management fee. RICFX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. RICFX, with annual returns of 14.76% over the last five years, is a well-diversified fund with a long track record of success.

Macquarie Emerging Markets A (DEMAX Quick QuoteDEMAX - Free Report) . Expense ratio: 1.42%. Management fee: 1.13%. Five year annual return: 28.17%. DEMAX is a part of the Non US - Equity fund category, many of which will focus across all cap levels, and will typically allocate their investments between emerging and developed markets.

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.