Investing in mutual funds for retirement is never too late. And the Zacks Mutual Fund Rank can be an excellent tool for investors looking to invest in the best funds.

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.

AQR Large Cap Momentum Style N (AMONX Quick QuoteAMONX - Free Report) has a 0.65% expense ratio and 0.25% management fee. AMONX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. With yearly returns of 14.42% over the last five years, this fund clearly wins.

Neuberger Berman Genesis Adviser (NBGAX Quick QuoteNBGAX - Free Report) : 1.34% expense ratio and 1.06% management fee. NBGAX is a Small Cap Value fund, and these funds are known for investing in companies with market caps under $2 billion. NBGAX, with annual returns of 11.86% over the last five years, is a well-diversified fund with a long track record of success.

Vanguard Windsor-II Admiral (VWNAX Quick QuoteVWNAX - Free Report) is an attractive large-cap allocation. VWNAX 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. VWNAX has an expense ratio of 0.26%, management fee of 0.25%, and annual returns of 14.96% over the past five years.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.