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 investors' portfolios.

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

Brown Advisory Flexible Equity Institutional (BAFFX Quick QuoteBAFFX - Free Report) : 0.52% expense ratio and 0.43% management fee. BAFFX is an Allocation Balanced mutual fund. Allocation Balanced funds look to invest across asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual; these funds are mostly categorized by their respective asset allocation. BAFFX has achieved five-year annual returns of an astounding 15.11%.

Shelton Equity Income K (EQTKX): 1.15% expense ratio and 0.45% management fee. EQTKX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. EQTKX, with annual returns of 11.88% over the last five years, is a well-diversified fund with a long track record of success.

Fidelity Select Energy Portfolio (FSENX). Expense ratio: 0.65%. Management fee: 0.64%. Five year annual return: 25.66%. FSENX is a Sector - Energy mutual fund, which encompasses a wide range of vastly changing and vitally important industries throughout this massive global sector.

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.