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.

Brown Advisory Flexible Equity Institutional (BAFFX Quick QuoteBAFFX - Free Report) has a 0.54% expense ratio and 0.43% management fee. BAFFX is a part of the Allocation Balanced fund category; these funds like to invest in a variety of asset types, finding a balance between stocks, bonds, cash, and sometimes even precious metals and commodities; they are mostly categorized by their respective asset allocation. With yearly returns of 11.54% over the last five years, this fund clearly wins.

Elfun Trusts (ELFNX Quick QuoteELFNX - Free Report) is a stand out amongst its peers. ELFNX is part of the Large Cap Blend section, and these mutual funds most often invest in firms with a market capitalization of $10 billion or more. By investing in bigger companies, these funds offer more stability, and are often well-suited for investors with a "buy and hold" mindset. With five-year annualized performance of 13.03%, expense ratio of 0.18% and management fee of 0.14%, this diversified fund is an attractive buy with a strong history of performance.

Fidelity Advisor Growth Opportunit (FAOFX Quick QuoteFAOFX - Free Report) : 0.01% expense ratio and 0% management fee. FAOFX 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. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 15.36% over the last five years.

These examples highlight the fact that there are some astonishingly good mutual funds out there. If your advisor has you in the good ones, bravo! If not, you may need to have a talk.