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 easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

American Century Investments Focused Dynamic Growth Investor (ACFOX Quick QuoteACFOX - Free Report) has a 0.86% expense ratio and 0.85% management fee. ACFOX 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 yearly returns of 12.85% over the last five years, this fund clearly wins.

Fidelity Advisor Semiconductors M (FELTX Quick QuoteFELTX - Free Report) . Expense ratio: 1.25%. Management fee: 0.52%. FELTX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. This fund has managed to produce a robust 18.35% over the last five years.

Lord Abbett Micro Cap Growth I (LMIYX Quick QuoteLMIYX - Free Report) : 1.14% expense ratio and 0.9% management fee. LMIYX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets. With a five-year annual return of 14.8%, 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.