This January, Germany was up 10.5 percent compared with last year's slow January.
But France was down 5.6 percent after it imposed gas-guzzler fines of up to 2,600 euros, or $3,854 at current exchange rates.
Italy was off 7.3 percent because many consumers had bought cars in 2007, expecting government incentives to end Jan. 1. Italy renewed old-car trade-in incentives for 2008 but did so very late in 2007.
Total European volume slipped 0.3 percent to 1,308,761 units, said ACEA, the European automakers' association.
Two other countries with January tax changes also had sales swings, said Nigel Griffiths, director of international automotive research for Global Insight.
Finland's sales jumped 27.4 percent after it cut taxes on fuel-efficient cars.
In the Netherlands, the market fell 3.3 percent because some people had bought cars last year to avoid the new-year tax increase on big cars.
"It's a big distortion," Griffiths said.
He said the French decline in January would have been greater except that the government didn't agree on its new-year purchase-tax penalty until mid-December, limiting the chance to beat the tax to a few weeks.
"Still, you had a spike in December SUV and premium-brand sales," Griffiths said. "And dealers were pre-registering cars they didn't have yet to avoid the penalties."