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 break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

Brandes International Small Cap Equity I

(BISMX Quick QuoteBISMX - Free Report) has a 1.15% expense ratio and 0.95% management fee. BISMX is a Non US - Equity option, focusing their investments acoss emerging and developed markets, and can often extend across cap levels too. With yearly returns of 17.26% over the last five years, this fund clearly wins.

JPMorgan Intrepid Growth Fund R2

(JIGZX Quick QuoteJIGZX - Free Report) is a stand out amongst its peers. JIGZX 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 17.89%, expense ratio of 1.09% and management fee of 0.3%, this diversified fund is an attractive buy with a strong history of performance.

Permanent Portfolio Permanent I

(PRPFX Quick QuotePRPFX - Free Report) . Expense ratio: 0.82%. Management fee: 0.79%. Five year annual return: 10.77%. PRPFX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual.

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.