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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Fidelity Advisor Diversified Stock A (FDTOX Quick QuoteFDTOX - Free Report) : 0.79% expense ratio and 0.4% management fee. FDTOX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. FDTOX has achieved five-year annual returns of an astounding 11.9%.

JPMorgan Growth Advantage I (JGASX Quick QuoteJGASX - Free Report) : 0.79% expense ratio and 0.55% management fee. JGASX 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. JGASX, with annual returns of 15.56% over the last five years, is a well-diversified fund with a long track record of success.

Janus Henderson Enterprise I (JMGRX Quick QuoteJMGRX - Free Report) is an attractive large-cap allocation. JMGRX is a Mid Cap Growth mutual fund. These funds aim to target companies with a market capitalization between $2 billion and $10 billion that are also expected to exhibit more extensive growth opportunities for investors than their peers. JMGRX has an expense ratio of 0.77%, management fee of 0.64%, and annual returns of 10.76% 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.