Last month’s interest rate increase made a small impact on automotive borrowers’ cost to buy, but it and a potential additional hike this month add to increasingly eroding consumer affordability, Cox Automotive says.

The company’s analysts estimate that the Federal Reserve’s quarter-point hike on Sept. 16 added just $6 to the average U.S. new-car payment and $4 in the used segment.

However minor that may seem, it’s one more addition to consumers’ ballooning budgets due to inflation from many fronts that sent the consumer price index up 0.6% last month for 3.7% annual inflation, the Bureau of Labor Statistics reported.

The inflation rate is well above the Federal Reserve’s target 2% and makes it more likely that the Fed will again raise interest rates in an attempt to cool inflation when it meets late this month.

Gas prices, which jumped 9% in September for a 34% gain over the past 12 months, according to the bureau, pushed up overall inflation as the war in the Middle East continues, squeezing supply.

Meanwhile, historically high diesel fuel prices, which have an outsize affect on prices of many other products due to increased transport costs, “will almost certainly get passed on to consumers,” Cox Chief Economist Jeremy Robb said.

The cost pressures come as auto consumers find the greatest access to car loans in more than a decade, Cox reported this week. But with high unit prices – $50,562 on average in September – squeezing purchases into already strained budgets presents a challenge.