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.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

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

Fidelity OTC Portfolio K (FOCKX Quick QuoteFOCKX - Free Report) : 0.76% expense ratio and 0.66% management fee. FOCKX 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. FOCKX has achieved five-year annual returns of an astounding 13.98%.

LKCM Equity Institutional (LKEQX Quick QuoteLKEQX - Free Report) : 0.8% expense ratio and 0.7% management fee. LKEQX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. LKEQX, with annual returns of 11.86% over the last five years, is a well-diversified fund with a long track record of success.

T. Rowe Price New Horizons I (PRJIX Quick QuotePRJIX - Free Report) . Expense ratio: 0.65%. Management fee: 0.63%. Five year annual return: 13.41%. PRJIX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets.

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.