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, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

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

Dreyfus Strategic Value Y (DRGYX Quick QuoteDRGYX - Free Report) : 0.63% expense ratio and 0.6% management fee. DRGYX 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. With annual returns of 14.14% over the last five years, this fund is a winner.

Fidelity Growth Strategies Fund (FDEGX Quick QuoteFDEGX - Free Report) : 0.75% expense ratio and 0.56% management fee. FDEGX is an All Cap Growth mutual fund. In order to increase diversification, these funds have holdings across small, medium, and large-cap levels. With yearly returns of 12.66% over the last five years, FDEGX is an effectively diversified fund with a long reputation of solidly positive performance.

PGIM Jennison Health Sciences R (PJHRX Quick QuotePJHRX - Free Report) is an attractive large-cap allocation. PJHRX is part of the Sector - Health category, offering investors a focus on the healthcare industry, one of the largest sectors in the American economy. PJHRX has an expense ratio of 1.48%, management fee of 0.73%, and annual returns of 11.2% 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.