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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

American Funds Washington Mutual Investors 529C (CWMCX Quick QuoteCWMCX - Free Report) has a 1.35% expense ratio and 0.22% management fee. CWMCX is a Large Cap Value fund. These funds invest in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. With yearly returns of 14.09% over the last five years, this fund clearly wins.

JPMorgan US Equity Fund R6 (JUEMX). Expense ratio: 0.44%. Management fee: 0.4%. JUEMX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. This fund has managed to produce a robust 16.02% over the last five years.

MFS International Growth R4 (MGRVX): 0.8% expense ratio and 0.67% management fee. MGRVX 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. With a five-year annual return of 10.73%, this fund is a well-diversified fund with a long track record of success.

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.