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.

Hotchkis and Wiley Small Cap Value I (HWSIX Quick QuoteHWSIX - Free Report) : 0.97% expense ratio and 0.75% management fee. HWSIX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. With annual returns of 13.54% over the last five years, this fund is a winner.

AQR Large Cap Momentum Style R6 (QMORX Quick QuoteQMORX - Free Report) . Expense ratio: 0.3%. Management fee: 0.25%. QMORX 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. This fund has managed to produce a robust 14.97% over the last five years.

RBC Small Cap Core Fund I (RCSIX Quick QuoteRCSIX - Free Report) . Expense ratio: 0.9%. Management fee: 0.85%. Five year annual return: 10.35%. RCSIX is a Small Cap Growth mutual fund building their portfolio around stocks with market caps under $2 billion and large growth opportunities.

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.