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.

Goldman Sachs Flexible Cap R6 (GFCUX Quick QuoteGFCUX - Free Report) : 0.58% expense ratio and 0.55% management fee. GFCUX 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. GFCUX has achieved five-year annual returns of an astounding 12.68%.

BlackRock Long-Horizon Equity A (MDEGX Quick QuoteMDEGX - Free Report) . Expense ratio: 1.2%. Management fee: 0.8%. MDEGX 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. This fund has managed to produce a robust 11.79% over the last five years.

Vanguard Windsor-II Investor (VWNFX Quick QuoteVWNFX - Free Report) . Expense ratio: 0.34%. Management fee: 0.33%. Five year annual return: 10.94%. VWNFX is a part of the Large Cap Value category, and invests in equities with a market capitalization of $10 billion or more, but whose share prices do not reflect their intrinsic value.

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.