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 learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

If you are looking to diversify your portfolio, consider AB Large Cap Growth I (ALLIX Quick QuoteALLIX - Free Report) . ALLIX 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. This fund is a winner, boasting an expense ratio of 0.6%, management fee of 0.48%, and a five-year annualized return track record of 11.07%.

Black Oak Emerging Technology Fund (BOGSX Quick QuoteBOGSX - Free Report) . Expense ratio: 1.03%. Management fee: 0.74%. BOGSX is part of the Sector - Tech mutual fund category that invests in technology and lets investors own a stake in a notoriously volatile sector, but with a much more diversified approach. This fund has managed to produce a robust 12.96% over the last five years.

Janus Henderson Global Life Science A (JFNAX Quick QuoteJFNAX - Free Report) . Expense ratio: 0.98%. Management fee: 0.64%. Five year annual return: 10.11%. JFNAX is a Sector - Health mutual fund, which give investors an opportunity to focus on healthcare, one of the largest sectors of the American economy.

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.