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

Fidelity Select Health Care Services (FSHCX Quick QuoteFSHCX - Free Report) : 0.71% expense ratio and 0.52% management fee. FSHCX is part of the Sector - Health category, offering investors a focus on the healthcare industry, one of the largest sectors in the American economy. FSHCX has achieved five-year annual returns of an astounding 11.93%.

Pioneer Fundamental Growth Y (FUNYX Quick QuoteFUNYX - Free Report) . Expense ratio: 0.75%. Management fee: 0.61%. FUNYX 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 10.94% over the last five years.

Neuberger Berman Guardian Trust (NBGTX Quick QuoteNBGTX - Free Report) is an attractive large-cap allocation. NBGTX 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. NBGTX has an expense ratio of 1.03%, management fee of 0.88%, and annual returns of 10.68% 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.