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, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

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

DFA US Micro Cap Institutional (DFSCX Quick QuoteDFSCX - Free Report) : 0.42% expense ratio and 0.38% management fee. DFSCX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. DFSCX has achieved five-year annual returns of an astounding 15.04%.

Goldman Sachs Growth Strategy Service Class (GGSSX): 0.69% expense ratio and 0.15% management fee. GGSSX is a Global - Equity mutual fund. These funds invest in large markets like the U.S., Europe, and Japan, and operate with very few geographical limitations GGSSX, with annual returns of 10.61% over the last five years, is a well-diversified fund with a long track record of success.

T. Rowe Price Capital Appreciation Fund (PRWCX) is an attractive large-cap allocation. PRWCX is an All Cap Value mutual fund, which invests in small, medium, and large-cap companies, though they end up focusing on bigger firms due to percentage of assets. PRWCX has an expense ratio of 0.7%, management fee of 0.58%, and annual returns of 11.89% 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.