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

Cambiar SMID Fund Investor (CAMMX Quick QuoteCAMMX - Free Report) has a 0.93% expense ratio and 0.8% management fee. CAMMX is a Mid Cap Value mutual funds that aims to target medium-sized companies that possess strong value and income opportunities for investors. With yearly returns of 10.66% over the last five years, this fund clearly wins.

JPMorgan Small Cap Growth Fund R6 (JGSMX Quick QuoteJGSMX - Free Report) . Expense ratio: 0.74%. Management fee: 0.65%. JGSMX is a Small Cap Growth mutual fund and tends to feature small companies in up-and-coming industries and markets. This fund has managed to produce a robust 7.64% over the last five years.

Royce PA Mutual Fund Investor (PENNX Quick QuotePENNX - Free Report) : 0.94% expense ratio and 0.76% management fee. PENNX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. The fund is mainly invested in equities, has a long reputation of salutary performance, and has yearly returns of 10.16% 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.