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 best way to shortlist great mutual funds is to ensure solid performance, diversification, and low fees. Some are better than others, but utilizing the Zacks Mutual Fund Rank, we have identified three mutual funds that could be solid additions to one's retirement portfolio.

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

Oberweis Small-Cap Opportunities (OBSOX Quick QuoteOBSOX - Free Report) has a 1.25% expense ratio and 0.8% management fee. OBSOX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets. With yearly returns of 16.18% over the last five years, this fund clearly wins.

Fidelity Advisor Technology M (FATEX Quick QuoteFATEX - Free Report) is a stand out amongst its peers. FATEX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. With five-year annualized performance of 14.56%, expense ratio of 1.21% and management fee of 0.52%, this diversified fund is an attractive buy with a strong history of performance.

Eaton Vance Atlanta Cap Focus Growth A (EAALX Quick QuoteEAALX - Free Report) : 1.03% expense ratio and 0.65% management fee. EAALX is a Large Cap Growth option; these mutual funds purchase stakes in numerous large U.S. companies that are expected to develop and grow at a faster rate than other large-cap stocks. With a five-year annual return of 15.6%, this fund is a well-diversified fund with a long track record of success.

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.