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 investors' portfolios.

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

Hartford Real Asset Y (HRLYX Quick QuoteHRLYX - Free Report) : 0.9% expense ratio and 0.8% management fee. HRLYX is a Global - Equity mutual fund investing in bigger markets like the U.S., Europe, and Japan; these kinds of funds aren't limited by geography. With annual returns of 10.28% over the last five years, this fund is a winner.

Vanguard International Core Stock Admiral (VZICX) is a stand out amongst its peers. VZICX is a Non US - Equity fund. Many of these funds like to allocate across emerging and developed markets, and will often focus on all cap levels. With five-year annualized performance of 10.77%, expense ratio of 0.38% and management fee of 0.35%, this diversified fund is an attractive buy with a strong history of performance.

TCW Relative Value Large Cap N (TGDVX) is an attractive large-cap allocation. TGDVX 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. TGDVX has an expense ratio of 0.85%, management fee of 0.6%, and annual returns of 11.36% 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.