It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

The easiest way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. Using the Zacks Mutual Fund Rank of over 19,000 mutual funds, we've identified three outstanding mutual funds that are ideally suited to help long-term investors pursue and achieve their retirement investing goals.

Let's learn about some of Zacks' highest ranked mutual funds with low fees you may want to consider.

Franklin Convertible Securities Adviser (FCSZX Quick QuoteFCSZX - Free Report) : 0.58% expense ratio and 0.46% management fee. FCSZX is a Convertible Bonds mutual fund, and these funds are unique in the fixed income world; these securities have components of both fixed income and equity, making them hybrid securities. With annual returns of 11.15% over the last five years, this fund is a winner.

MFS Mass Investors Growth Stock I (MGTIX Quick QuoteMGTIX - Free Report) : 0.46% expense ratio and 0.33% management fee. MGTIX 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. MGTIX, with annual returns of 12% over the last five years, is a well-diversified fund with a long track record of success.

Neuberger Berman Guardian Adviser (NBGUX Quick QuoteNBGUX - Free Report) : 1.17% expense ratio and 0.88% management fee. NBGUX 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. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 10.71% over the last 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.