There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

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.

Neuberger Berman Guardian Institutional (NGDLX): 0.69% expense ratio and 0.63% management fee. NGDLX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value. With annual returns of 14.4% over the last five years, this fund is a winner.

Nuveen Winslow Large-Cap Growth A (NWCAX): 0.91% expense ratio and 0.64% management fee. NWCAX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. NWCAX, with annual returns of 12.82% over the last five years, is a well-diversified fund with a long track record of success.

Victory Sycamore Established Value Y (VEVYX) is an attractive large-cap allocation. VEVYX is a Mid Cap Value fund, which usually invests in companies with a stock market valuation between $2 billion and $10 billion. VEVYX has an expense ratio of 0.64%, management fee of 0.45%, and annual returns of 10.58% 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.

Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report

Get Your Free (NGDLX): Fund Analysis Report

Get Your Free (VEVYX): Fund Analysis Report

Get Your Free (NWCAX): Fund Analysis Report

To read this article on Zacks.com click here.

Zacks Investment Research