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.

Sterling Capital Equity Income I (BEGIX Quick QuoteBEGIX - Free Report) : 0.79% expense ratio and 0.55% management fee. BEGIX is classified as a Large Cap Blend fund. More often than not, Large Cap Blend mutual funds invest in companies with a market cap of over $10 billion. Buying stakes in bigger companies offer these funds more stability, and are well-suited for investors with a "buy and hold" mindset. BEGIX has achieved five-year annual returns of an astounding 10.34%.

Calvert Equity Portfolio I (CEYIX Quick QuoteCEYIX - Free Report) . Expense ratio: 0.65%. Management fee: 0.55%. CEYIX 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. This fund has managed to produce a robust 13.56% over the last five years.

Wells Fargo Special Technology Admiral (WFTDX Quick QuoteWFTDX - Free Report) is an attractive large-cap allocation. With a much more diversified approach, WFTDX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. WFTDX has an expense ratio of 1.2%, management fee of 0.85%, and annual returns of 9.41% over the past 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.