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

AQR Small Cap Multi-Style N (QSMNX Quick QuoteQSMNX - Free Report) : 0.88% expense ratio and 0.45% management fee. QSMNX is a Small Cap Blend mutual fund, allowing investors a way to diversify their funds among various types of small-cap stocks. With annual returns of 11.02% over the last five years, this fund is a winner.

American Funds New Economy R5 (RNGFX): 0.45% expense ratio and 0.36% management fee. RNGFX 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 RNGFX, with annual returns of 12.82% over the last five years, is a well-diversified fund with a long track record of success.

Thornburg International Value R5 (TIVRX). Expense ratio: 0.9%. Management fee: 0.75%. Five year annual return: 10.71%. TIVRX is a part of the Non US - Equity fund category, many of which will focus across all cap levels, and will typically allocate their investments between emerging and developed markets.

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.