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 take a look at some of our top-ranked mutual funds with the lowest fees.

AQR Global Equity Fund I (AQGIX Quick QuoteAQGIX - Free Report) : 0.8% expense ratio and 0.6% management fee. AQGIX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations. AQGIX has achieved five-year annual returns of an astounding 10.78%.

Columbia Small Cap Value I Class Y (CSVYX Quick QuoteCSVYX - Free Report) : 0.86% expense ratio and 0.81% management fee. CSVYX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. CSVYX, with annual returns of 11.89% over the last five years, is a well-diversified fund with a long track record of success.

Fidelity Select Health Care Services (FSHCX Quick QuoteFSHCX - Free Report) . Expense ratio: 0.73%. Management fee: 0.53%. Five year annual return: 12.72%. FSHCX is part of the Sector - Health category, offering investors a focus on the healthcare industry, one of the largest sectors in the American economy.

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.