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.

Allspring Discipl US Core R6 (EVSRX Quick QuoteEVSRX - Free Report) : 0.43% expense ratio and 0.35% management fee. EVSRX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. EVSRX has achieved five-year annual returns of an astounding 11.85%.

Brown Advisory Sustainable Growth Ist (BAFWX Quick QuoteBAFWX - Free Report) . Expense ratio: 0.62%. Management fee: 0.55%. BAFWX 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. This fund has managed to produce a robust 17.62% over the last five years.

WCM International SmCap Growth Inst (WCMSX Quick QuoteWCMSX - Free Report) is an attractive large-cap allocation. WCMSX is a Non US - Equity option, focusing their investments acoss emerging and developed markets, and can often extend across cap levels too. WCMSX has an expense ratio of 1.25%, management fee of 1%, and annual returns of 11.07% over the past five years.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.