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

Fidelity Select Tech Hardware

(FDCPX Quick QuoteFDCPX - Free Report) has a 0.72% expense ratio and 0.68% management fee. FDCPX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. With yearly returns of 18.92% over the last five years, this fund clearly wins.

Voya Large Cap Value Portfolio S

(IPESX Quick QuoteIPESX - Free Report) . Expense ratio: 0.89%. Management fee: 0.75%. IPESX is a Large Cap Value mutual fund, which invests in stocks with a market cap of $10 billion of more, but whose share prices do not reflect their intrinsic value. This fund has managed to produce a robust 11.95% over the last five years.

Vanguard PRIMECAP Fund Investor

(VPMCX Quick QuoteVPMCX - Free Report) : 0.38% expense ratio and 0.37% management fee. VPMCX 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. With a five-year annual return of 14.16%, 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.