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 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.

AB Lg Cap Growth Z (APGZX Quick QuoteAPGZX - Free Report) has a 0.51% expense ratio and 0.48% management fee. APGZX 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 yearly returns of 11.18% over the last five years, this fund clearly wins.

Bridgeway Small Cap Value N (BRSVX Quick QuoteBRSVX - Free Report) . Expense ratio: 0.83%. Management fee: 0.61%. BRSVX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. This fund has managed to produce a robust 14.62% over the last five years.

Dreyfus Appreciation Fund Y (DGYGX Quick QuoteDGYGX - Free Report) . Expense ratio: 0.59%. Management fee: 0.55%. Five year annual return: 10.71%. DGYGX 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.

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.