There is never a wrong time to invest in mutual funds for retirement. So, if you're still looking for the best mutual funds, the Zacks Mutual Fund Rank can be a great guide.

The best way to shortlist great mutual funds is to ensure solid performance, diversification, and low fees. Some are better than others, but utilizing the Zacks Mutual Fund Rank, we have identified three mutual funds that could be solid additions to one's retirement portfolio.

Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

If you are looking to diversify your portfolio, consider Victory Sycamore Established Value I (VEVIX Quick QuoteVEVIX - Free Report) . VEVIX is a Mid Cap Value mutual fund, which targets medium-sized companies with a market cap between $2 billion and $10 billion. This fund is a winner, boasting an expense ratio of 0.58%, management fee of 0.45%, and a five-year annualized return track record of 9.19%.

Dreyfus Fund (DREVX Quick QuoteDREVX - Free Report) . Expense ratio: 0.71%. Management fee: 0.65%. DREVX 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. This fund has managed to produce a robust 12.75% over the last five years.

Principal Capital Appreciation R1 (PCAMX Quick QuotePCAMX - Free Report) : 1.32% expense ratio and 0.44% management fee. PCAMX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. With a five-year annual return of 10.61%, this fund is a well-diversified fund with a long track record of success.

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.