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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Fidelity Advisor Series Equity Growth

(FMFMX Quick QuoteFMFMX - Free Report) : 0.01% expense ratio and 0% management fee. FMFMX 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. FMFMX has achieved five-year annual returns of an astounding 17.88%.

Invesco Technology Fund Y

(ITYYX Quick QuoteITYYX - Free Report) is a stand out amongst its peers. With a much more diversified approach, ITYYX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. With five-year annualized performance of 11.5%, expense ratio of 0.77% and management fee of 0.62%, this diversified fund is an attractive buy with a strong history of performance.

Federated International Small-Mid Company Institutional

(ISCIX Quick QuoteISCIX - Free Report) : 0.99% expense ratio and 0.9% management fee. ISCIX is a Non US - Equity option, focusing their investments acoss emerging and developed markets, and can often extend across cap levels too. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 11.34% over the last five years.

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.