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.

BNY Mellon Natural Resources I (DLDRX Quick QuoteDLDRX - Free Report) : 0.91% expense ratio and 0.75% management fee. DLDRX is a Sector - Energy mutual fund, which encompasses a wide range of vastly changing and vitally important industries throughout this massive global sector. With annual returns of 13.81% over the last five years, this fund is a winner.

Fidelity Advisor Semiconductors A (FELAX Quick QuoteFELAX - Free Report) . Expense ratio: 1.01%. Management fee: 0.52%. FELAX is part of the Sector - Tech mutual fund category that invests in technology and lets investors own a stake in a notoriously volatile sector, but with a much more diversified approach. This fund has managed to produce a robust 16.06% over the last five years.

MainStay Large Cap Growth R1 (MLRRX Quick QuoteMLRRX - Free Report) is an attractive large-cap allocation. MLRRX 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. MLRRX has an expense ratio of 0.78%, management fee of 0.61%, and annual returns of 10.21% 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.