It is never too late to invest in mutual funds for retirement. As such, if you plan to invest in some of the best funds, the Zacks Mutual Fund Rank can provide you with valuable guidance.

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.

Here are the funds that have achieved the Zacks Mutual Fund Rank #1 (Strong Buy) and have low fees.

Oppenheimer SteelPath MLP Income A (MLPDX Quick QuoteMLPDX - Free Report) has a 1.4% expense ratio and 0.95% management fee. MLPDX is a Sector - Energy mutual fund, which encompasses a wide range of vastly changing and vitally important industries throughout this massive global sector. With yearly returns of 11.57% over the last five years, this fund clearly wins.

Putnam Large Cap Value A (PEYAX Quick QuotePEYAX - Free Report) is a stand out amongst its peers. PEYAX 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. With five-year annualized performance of 13.14%, expense ratio of 0.9% and management fee of 0.47%, this diversified fund is an attractive buy with a strong history of performance.

Queens Road Small Cap Value Fund (QRSVX Quick QuoteQRSVX - Free Report) : 0.98% expense ratio and 0.66% management fee. QRSVX is a Small Cap Value mutual fund option, which typically invest in companies with market caps under $2 billion. With a five-year annual return of 10.04%, this fund is a well-diversified fund with a long track record of success.

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.