MORGAN STANLEY: US consumers just aren't spending their gas savings like we thought they would

US consumers are getting more cautious about how they spend their savings from low gas prices.

Gas prices have fallen 40% since September, giving consumers a 'tax break' of more than $60 billion, according to Morgan Stanley chief US economist Ellen Zentner.

As gas prices fell, the pace of real Personal Consumption Expenditures (PCE) growth accelerated above the 2% average of the last four years, Zentner said in a video Friday. It reached 4.3% for the fourth quarter of 2014.

Yet, that was less than what it could have been.

"What we found is some lingering caution, that sales could actually be stronger," Zentner said. "So some of the discretionary categories have shown some weakening of late. Households simply aren't spending as much out of the gas savings as we thought they would."

"That lingering caution we think continues in the first quarter," she added, showing that real PCE growth is estimated to fall to 3.2% for the first quarter. The benefit of the slowdown in spending is that people are using the extra money to pay off debt, or are stashing it away as savings, Zentner said. This ultimately improves households' finances.

Here's a chart that shows the estimated slowdown in real PCE:

On Monday, Business Insider's Sam Ro explored this issue, noting that in the most recent University of Michigan consumer sentiment report, consumers expressed doubt that low gas prices would persist.

This caution has seen consumers opt to hang on to their gas savings rather than spend it.

President Obama had told US consumers to enjoy their savings from low gas prices because "they won't be around forever." Rather than splurge, Obama advised Americans to save.

One area where it appears Americans have been spending their extra savings is restaurants and bars. According to last week's January retail sales data, sales at restaurants and bars jumped 23% in January, the most among all categories of businesses.