The director of the Department of Natural Resources says Iowans need to buy more efficient vehicles. D-N-R director Paul Johnson says Iowans are buying too many trucks and sport utility vehicles which get poor gas mileage. However, Johnson isn’t ready to change license fees in Iowa so fees would be higher on low-mileage vehicles, like pick-up trucks.Iowans raised a ruckus when the Legislature raised mini-van license fees in 1992. Johnson says an alternative might be incentives for the purchase of fuel-efficient vehicles.Johnson says today’s high gas prices may be all the prompting Iowans need to steer toward fuel-efficient cars.