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 take a look at some of our top-ranked mutual funds with the lowest fees.

Amana Growth Investor (AMAGX Quick QuoteAMAGX - Free Report) : 0.9% expense ratio and 0.62% management fee. AMAGX 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 annual returns of 15.15% over the last five years, this fund is a winner.

Fidelity Select Tech Hardware (FDCPX Quick QuoteFDCPX - Free Report) is a stand out amongst its peers. With a much more diversified approach, FDCPX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. With five-year annualized performance of 12.98%, expense ratio of 0.72% and management fee of 0.53%, this diversified fund is an attractive buy with a strong history of performance.

Vanguard Dividend Growth Fund (VDIGX Quick QuoteVDIGX - Free Report) : 0.3% expense ratio and 0.26% management fee. VDIGX is a Large Cap Blend fund, targeting companies with market caps of over $10 billion. These funds offer investors a stability, and are perfect for people with a "buy and hold" mindset. With a five-year annual return of 12.68%, 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.