Car dealers in St. Louis say they can’t give much more to end a mechanics strike that will soon enter its third month. The dealers say they are losing business to independents and will continue to lose business if their costs keep going up. But their proposed solution doesn’t sit well with the International Association of Machinists. It called the strike two months ago, resisting the dealers’ proposal to use more lower-paid, less-skilled helpers to work beside the mechanics and bring costs down. Dealers say if the union won’t concede, there soon won’t be dealership service departments for their members to return to.