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, most reliable way to judge a mutual fund's quality over time is by analyzing its performance, diversification, and fees. The Zacks Mutual Fund Rank, which covers over 19,000 mutual funds, has helped us identify three outstanding options that are perfect for any long-term investors' portfolios that is retirement-focused.

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

Columbia Balanced Z

(CBALX Quick QuoteCBALX - Free Report) : 0.68% expense ratio and 0.57% management fee. CBALX is classified as an Allocation Balanced fund, which seeks to invest in a balance of asset types, like stocks, bonds, and cash, and including precious metals or commodities is not unusual. With annual returns of 10.18% over the last five years, this fund is a winner.

Fidelity Advisor Semiconductors M

(FELTX Quick QuoteFELTX - Free Report) is a stand out amongst its peers. FELTX is a Sector - Tech mutual fund, allowing investors to own a stake in a notoriously volatile sector with a much more diversified approach. With five-year annualized performance of 33.4%, expense ratio of 1.22% and management fee of 0.53%, this diversified fund is an attractive buy with a strong history of performance.

MFS Mid Cap Value R4

(MVCJX Quick QuoteMVCJX - Free Report) is an attractive large-cap allocation. MVCJX is a Mid Cap Value fund, which usually invests in companies with a stock market valuation between $2 billion and $10 billion. MVCJX has an expense ratio of 0.74%, management fee of 0.61%, and annual returns of 11.42% over the past five years.

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.