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.

MassMutual Select Blue Chip Growth R3 (MBCNX Quick QuoteMBCNX - Free Report) : 1.36% expense ratio and 0.61% management fee. MBCNX is a part of the Large Cap Growth mutual fund category, which invest in many large U.S. companies that are expected to grow much faster compared to other large-cap stocks. With annual returns of 9.9% over the last five years, this fund is a winner.

Putnam Small Cap Growth Y (PSYGX Quick QuotePSYGX - Free Report) . Expense ratio: 1%. Management fee: 0.75%. PSYGX is one of many Small Cap Growth mutual funds; these funds tend to create their portfolios around stocks with market capitalization of less than $2 billion. This fund has managed to produce a robust 9.14% over the last five years.

Goldman Sachs Focused Value Instl (GFVSX Quick QuoteGFVSX - Free Report) : 0.72% expense ratio and 0.69% management fee. GFVSX 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. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 9.48% over the last 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.