Investing guru Jack Bogle warns savvy investors that the current volatile market environment indeed poses “hazardous times” when trying to obtain a significant return.

"These are hazardous times. These are not cheap times. In the market, one never knows what is coming next," Bogle recently told CNBC.

He warned individual investors to brace for slimmer returns.

"The first thing they should do is plan for the future on the assumption that returns will be much lower than they have been in the past," said Bogle, the founder of the Vanguard Group, the world’s largest provider of mutual funds with $4 trillion in global assets under management.

He said since the long bull market began in 1982, investors have seen a nominal average return of 12 percent, minus a 4 percent inflation rate, for an 8 percent real return.

Bogle says today "we're looking for a 4 percent nominal return and one and a half to 2 percent inflation, for a 1.5 to percent real return on your savings. That's a big, big difference."

Despite the prediction of a lower return on the horizon, Bogle stressed: "There is never an argument for not investing."

He advised a 50-50 blend of stock and bonds for "all investors of all types." But he argued that if you're younger, an allocation of 80 percent stocks and 20 percent bonds might be a reasonable mix. And "when you're older, depending on circumstances, 40 percent or 30 percent in stocks and 70 percent in bonds."

Bogle shared his message for retirement investors: Own the stock market and diversify, buy in at low-cost, invest for the long term and don't trade. "I think in general the best rule is 'stay the course,'" he said.

The investor has another rule: "When you get your retirement plan statement every month, don't open it. Don't peek. When you retire, open the statement and believe me if you've been putting money in there for 40 or 50 years, you'll need a cardiologist standing by you when you open it."

Meanwhile, Bogle is offering some advice to active managers amid the continuing shift to passive funds.

“Do nothing, just stand there,” he said at the 2017 Morningstar Investment Conference, Financial Advisor reports.

The 87-year-old retired chief executive of Vanguard said major mutual fund conglomerates shouldn’t change their mutual fund businesses but should expand into other business lines in order to survive in the long run, the publication said. 

Bogle said active managers should refrain from trying to imitate the low fees of index funds or introduce their own index-fund lineups, Barron's reported.

“Maintain your fund business as the ‘cash cow’ that it is today, delivering high margins and generous profits, albeit likely at a declining rate,” Bogle was quoted saying. “Don’t invest more capital. Don’t cut management fees. Nominal cuts won’t help, and severe cuts would eliminate those cash flows. While fund cash outflows are highly likely to continue, a sharply rising stock market, however unlikely, would help offset the outflows, slowing the declines in assets under management, fee revenues and profits.”

And you'd be wise to follow Bogle's advice. Why?

Because one of the most respected investment gurus of all time recently cited Bogle as his hero.

Billionaire investor Warren Buffett praised Bogle in his annual letter to Berkshire Hathaway Inc. shareholders.

The pioneer of indexing was once an outcast in the investment world as he eschewed riches to provide real value to American investors, Buffett wrote.

“In his early years, Jack was frequently mocked by the investment-management industry,” Buffett wrote. “Today, however, he has the satisfaction of knowing that he helped millions of investors realize far better returns on their savings than they otherwise would have earned. He is a hero to them and to me.”

Bogle started the indexing revolution for retail investors in 1976 when he launched the Vanguard 500 Index Fund. The fund, which just passed its 40th anniversary, had $205 billion in assets as of Aug. 31, Bloomberg reported.

(Newsmax wire services contributed to this report).