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.

How can you tell a good mutual fund from a bad one? It's pretty basic: if the fund is diversified, has low fees, and shows strong performance, it's a keeper. Of course, there's a wide range, but using the Zacks Mutual Fund Rank, we've found three mutual funds that would be great additions to any long-term retirement investors' portfolios.

Let's break down some of the mutual funds with the top Zacks Mutual Fund Rank and the lowest fees.

If you are looking to diversify your portfolio, consider Hotchkis and Wiley Small Cap Value A (HWSAX Quick QuoteHWSAX - Free Report) . HWSAX is a Small Cap Value fund, and these funds are known for investing in companies with market caps under $2 billion. This fund is a winner, boasting an expense ratio of 1.2%, management fee of 0.75%, and a five-year annualized return track record of 13.32%.

T. Rowe Price Blue Chip Growth R (RRBGX Quick QuoteRRBGX - Free Report) is a stand out amongst its peers. RRBGX 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 five-year annualized performance of 12.57%, expense ratio of 1.22% and management fee of 0.55%, this diversified fund is an attractive buy with a strong history of performance.

JPMorgan Mid Cap Growth I (HLGEX Quick QuoteHLGEX - Free Report) : 0.89% expense ratio and 0.65% management fee. HLGEX is a Mid Cap Growth mutual fund. These mutual funds choose companies with a stock market valuation between $2 billion and $10 billion. With a five-year annual return of 13.32%, 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.