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

Fidelity Select Technology (FSPTX Quick QuoteFSPTX - Free Report) : 0.69% expense ratio and 0.52% management fee. With a much more diversified approach, FSPTX--part of the Sector - Tech mutual fund category--gives investors a way to own a stake in the notoriously risky tech sector. With annual returns of 13.45% over the last five years, this fund is a winner.

Lord Abbett Growth Leaders A (LGLAX Quick QuoteLGLAX - Free Report) . Expense ratio: 0.91%. Management fee: 0.51%. LGLAX 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. This fund has managed to produce a robust 11.4% over the last five years.

Virtus KAR Small-Cap Core I (PKSFX Quick QuotePKSFX - Free Report) is an attractive large-cap allocation. PKSFX is a Small Cap Blend mutual fund, and usually targets stocks with market caps of less than $2 billion, letting investors diversify their funds among other kinds of small-cap equities. PKSFX has an expense ratio of 1.01%, management fee of 0.75%, and annual returns of 13.87% over the past 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.