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.

TIAA-CREF Large Cap Growth Premier (TILPX Quick QuoteTILPX - Free Report) : 0.54% expense ratio and 0.4% management fee. TILPX is a Large Cap Growth mutual fund, and these funds invest in many large U.S. firms that are projected to grow at a faster rate than their large-cap peers. With annual returns of 12.36% over the last five years, this fund is a winner.

Vanguard Health Care Investor (VGHCX Quick QuoteVGHCX - Free Report) . Expense ratio: 0.34%. Management fee: 0.33%. VGHCX is part of the Sector - Health category, offering investors a focus on the healthcare industry, one of the largest sectors in the American economy. This fund has managed to produce a robust 8.84% over the last five years.

Victory RS Global Growth R (RGGKX Quick QuoteRGGKX - Free Report) is an attractive large-cap allocation. RGGKX is a Global - Equity mutual fund, which invests their assets in large markets, leveraging the global economy. RGGKX has an expense ratio of 1.1%, management fee of 0.6%, and annual returns of 10.22% over the past five years.

We hope that your investment advisor (if you use one) has you invested in one or all of the top-ranked mutual funds we've reviewed. But if that isn't the case, it might be time to have a conversation or reconsider this vitally important relationship.