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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Causeway International Opportunities Investor (CIOVX Quick QuoteCIOVX - Free Report) has a 1.18% expense ratio and 0.8% management fee. CIOVX is a Non US - Equity option, focusing their investments acoss emerging and developed markets, and can often extend across cap levels too. With yearly returns of 13.12% over the last five years, this fund clearly wins.

JPMorgan Value Advantage R2 (JGAQX): 1.25% expense ratio and 0.5% management fee. JGAQX 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. With yearly returns of 10.81% over the last five years, JGAQX is an effectively diversified fund with a long reputation of solidly positive performance.

T. Rowe Price Large Cap Growth Inv (TRGOX) is an attractive large-cap allocation. TRGOX 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. TRGOX has an expense ratio of 0.7%, management fee of 0.54%, and annual returns of 10.11% 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.