January auto sales were down slightly in the Houston region from the same period a year earlier, but continued strong demand for trucks and SUVs pushed the average retail sales price to a new record, $36,357. In January, trucks and SUVs - 63.9 percent of retail vehicles sold in the Houston area - cost on average about $8,500 more than cars, InfoNation owner Steve McDowell said. In 2015, the average age of cars and light truck vehicles in operation on Houston-area roadways fell slightly to 8.67 years.