The 5-year Treasury is up 90 basis points since spring; auto loan rates have risen only about 20

The bond selloff is starting to reach car and truck loans. "Many auto loan interest rates move with the five-year or 10-year Treasury note," Patrick Manzi, chief economist of the National Automobile Dealers Association, told CNBC, adding that NADA expects auto loan rates to increase after the recent run-up in yields.

So far the move in loans has been small. New-vehicle loan rates rose about 20 basis points over the past two months and used-vehicle rates about 10, Cox Automotive chief economist Jeremy Robb wrote in a Sept. 21 report cited by CNBC.

The number behind the number: the benchmark moved much further

The averages most people quote are stale. CNBC cited Experian's figures for the second quarter of 2026: an average new-car loan rate of 6.35% and a used-car rate of about 11.2%. Those loans were written while the 5-year Treasury was a lot lower than it is now.

Using Treasury's daily yield data:

That is about 90 basis points of increase in the benchmark from the second-quarter average, against roughly 20 basis points in new-car loan rates. On Thursday morning the 5-year was trading above 5%, its highest since 2006, CNBC reported.

Two readings are possible, and both matter to a borrower. Lenders may be absorbing part of the move to keep volume up, in which case their margins are thinner and that is unlikely to last if yields stay here. Or the pass-through is simply slow, in which case more of the increase is still coming. Either way, a quote from this summer is not a guide to what a loan will cost in October.

Who it actually hits: the contractor financing a work truck

For most households a car loan is one purchase every few years. For a plumbing, HVAC or electrical business, vehicles are working capital, and a fleet gets replaced on a schedule. CheckThisBiz lists 40,729 independent HVAC companies, 27,975 plumbing businesses, 25,380 electrical contractors and 24,679 trucking firms, all businesses where the vehicle is the job site.

Take a $50,000 truck financed over 60 months. Our arithmetic:

The full pass-through adds about $21 a month and $1,270 over the loan for one truck. On a three-truck replacement cycle, that is about $3,800 in extra interest. It will not sink a business, but it is real money, and it arrives with WTI crude near $98 a barrel on Thursday afternoon. These are consumer averages; a business borrower's rate depends on its own credit and the lender, so treat the table as a guide to the size of the change, not the level.

Used vehicles start from a much higher base. At Experian's second-quarter averages, a used loan of $27,852 at 11.2% over about 68 months costs roughly $555 a month; nine-tenths of a point more would add about $13 a month.

What to do

If a vehicle purchase is already planned for this fall, the direction of the benchmark argues for locking financing sooner rather than later, and for getting quotes from more than one lender, since spreads look unsettled. If the purchase is optional, there is no urgency: the difference on one truck is tens of dollars a month, and the Fed's next moves will say more about where rates go than this week's trading. The Fed raised its target range to 3.75% to 4% last week, and Philadelphia Fed President Anna Paulson said on Thursday that "modest further tightening" may be needed.

Sources: U.S. Treasury; CNBC, citing NADA, Cox Automotive and Experian; CheckThisBiz business counts. Payment figures are our own calculations and exclude taxes and fees. This is market information, not investment advice.