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

If you are looking to diversify your portfolio, consider Fidelity Select Tech Hardware (FDCPX Quick QuoteFDCPX - Free Report) . With a much more diversified approach, FDCPX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. This fund is a winner, boasting an expense ratio of 0.72%, management fee of 0.53%, and a five-year annualized return track record of 15.44%.

Ivy Mid Cap Growth A (WMGAX Quick QuoteWMGAX - Free Report) . Expense ratio: 1.12%. Management fee: 0.77%. WMGAX is a Mid Cap Growth mutual fund. Mid Cap Growth funds pick stocks--usually companies with a market cap between $2 billion and $10 billion--that demonstrate extensive growth opportunities for investors compared to their peers. This fund has managed to produce a robust 14.92% over the last five years.

DFA US Large Cap Growth Institutional (DUSLX Quick QuoteDUSLX - Free Report) : 0.18% expense ratio and 0.15% management fee. DUSLX 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. With a five-year annual return of 14.19%, 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.