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 investors' portfolios.

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

Janus Henderson Global Technology S (JATSX): 1.19% expense ratio and 0.64% management fee. With a much more diversified approach, JATSX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. With annual returns of 13.57% over the last five years, this fund is a winner.

Victory Aggressive Growth Instl (UIAGX) is a stand out amongst its peers. UIAGX 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 five-year annualized performance of 12.22%, expense ratio of 0.72% and management fee of 0.42%, this diversified fund is an attractive buy with a strong history of performance.

Fidelity Equity Dividend Income K (FETKX Quick QuoteFETKX - Free Report) is an attractive large-cap allocation. FETKX 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. FETKX has an expense ratio of 0.46%, management fee of 0.45%, and annual returns of 12.73% over the past five years.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.