It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

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.

Nationwide Geneva Mid Cap Growth R6 (NWKAX Quick QuoteNWKAX - Free Report) has a 0.76% expense ratio and 0.64% management fee. NWKAX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion. With yearly returns of 11.72% over the last five years, this fund clearly wins.

Principal Large Cap Growth I R1 (PCRSX Quick QuotePCRSX - Free Report) is a stand out amongst its peers. PCRSX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. With five-year annualized performance of 13.25%, expense ratio of 1.47% and management fee of 0.6%, this diversified fund is an attractive buy with a strong history of performance.

TCW Relative Value Dividend Appreciation I (TGDFX Quick QuoteTGDFX - Free Report) : 0.7% expense ratio and 0.6% management fee. TGDFX is a Large Cap Value fund. These funds invest in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. With a five-year annual return of 12.09%, 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.