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

Invesco Comstock R5

(ACSHX Quick QuoteACSHX - Free Report) has a 0.52% expense ratio and 0.38% management fee. ACSHX 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. With yearly returns of 14.04% over the last five years, this fund clearly wins.

American Funds Growth and Income Portfolio R5

(RGNFX Quick QuoteRGNFX - Free Report) : 0.06% expense ratio and 0% management fee. RGNFX 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. With yearly returns of 10.53% over the last five years, RGNFX is an effectively diversified fund with a long reputation of solidly positive performance.

RBC SMID Cap Growth I

(TMCIX Quick QuoteTMCIX - Free Report) . Expense ratio: 0.82%. Management fee: 0.7%. Five year annual return: 10.84%. TMCIX is a Mid Cap Growth mutual fund. These funds aim to target companies with a market capitalization between $2 billion and $10 billion that are also expected to exhibit more extensive growth opportunities for investors than their peers.

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.