It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

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 take a look at some of our top-ranked mutual funds with the lowest fees.

Nuveen Core Equity Premier (TRPGX): 0.55% expense ratio and 0.39% management fee. TRPGX 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. TRPGX has achieved five-year annual returns of an astounding 10.87%.

Victory Global Equity Income (UGEIX): 1.01% expense ratio and 0.53% management fee. UGEIX is a Global - Equity mutual fund investing in bigger markets like the U.S., Europe, and Japan; these kinds of funds aren't limited by geography. UGEIX, with annual returns of 12.78% over the last five years, is a well-diversified fund with a long track record of success.

American Funds Washington Mutual Investors R1 (RWMAX Quick QuoteRWMAX - Free Report) : 1.35% expense ratio and 0.22% management fee. RWMAX 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. With a five-year annual return of 10.43%, this fund is a well-diversified fund with a long track record of success.

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.