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 break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

DFA US Small Cap Growth Institutional

(DSCGX Quick QuoteDSCGX - Free Report) : 0.32% expense ratio and 0.28% management fee. DSCGX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets. DSCGX has achieved five-year annual returns of an astounding 13.07%.

JPMorgan Intrepid Growth Fund A

(JIGAX Quick QuoteJIGAX - Free Report) is a stand out amongst its peers. JIGAX 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. With five-year annualized performance of 18.19%, expense ratio of 0.84% and management fee of 0.3%, this diversified fund is an attractive buy with a strong history of performance.

Sound Shore Fund

(SSHFX Quick QuoteSSHFX - Free Report) is an attractive large-cap allocation. SSHFX is an All Cap Value mutual fund, which invests in small, medium, and large-cap companies, though they end up focusing on bigger firms due to percentage of assets. SSHFX has an expense ratio of 0.95%, management fee of 0.75%, and annual returns of 12.7% over the past five years.

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.