I am the original poster. It seems like the thread took a very interesting turn. I like this discussion. Never mind my problem. I am taking the car to a mechanic tomorrow.
About torque on the lug nuts, I was told it is a dry torque spec. This means, the given specification is for tightening it without any lubrication on the threads.
I agree with TESTER that lubricating the threads, then tightening it to the same spec would over tighten it. However, technically, it is not over-torquing it. What is really is over-tightening it. When the lug nuts are tightened, the threads on the nut and the threads on the studs rub against each other and create resistence along with the friction caused by the face of the lug nut and the wheel. However, if there is lubricant on the threads, there would be less resistance from the threads and the surfaces, so the lug nut would turn a little more than if the lug nut were tightened without lubrication. But in both cases, the nut would stop turning when it reaches the specified torque. Put it in another way, the lug nut would have pulled/stretched the stud more if there were lubrication. This would be dangerous, which could cause premature failure–meaning breaking the stud. So, TESTER would not want to deal with such a car.
Then, the next quesiton is what do you need to do, if you want to lubricate the threads. It is common sense that lubricated threads would require less torque to pull the same amount. So, you would need to reduce the torque, if you want to lubricate. I was told the dry torque spec would have to be reduced by 20% or more if it is lubricated. You would have to do research to find out exactly how much. But this could cause a serious problem. With less torque (or friction, depending on the perspective) between the lug nuts and the studs, the wheels could come off. Is it the right wheels or the left wheels that are tightened backwards in military vehicles? The reason one side of the vehicle is tightened backwards is to prevent the wheels from coming off due to normal driving. For example, my car Ford Focus calls for 100 ft-lb of torque, but if I lubricate the threads, I would need to tighten them to 80 ft-lb or even less, depending on what type of lubrication I used.
Reducing the torque spec would be perfectly fine for stationary application. For example, if I have an outdoor structure that is not subject to vibration (such as people stepping on it repeatedly, swaying in the winds, etc.) and I am worried about the bolts rusting, I would lubricate the threads and reduce the torque accordingly. This is perfectly fine, because reduced torque when lubricated would provide exactly the same amount of force that pulls the two pieces of material together. So, if you lubricate and reduce the torque on the wheel lug nuts, the force that pulls the wheel to the hub would remain the same, but the friction between the threads and the friction between the bolt sufrace and the wheel would decrease. This would increase the possibility of the wheel coming loose when subject to vibration–such as driving the car. So, I agree with TESTER that lug nuts and studs should not be lubricated.
Another important issue is that the threads on the nut and the stud need to be clean. This is common sense, because any dirt trapped in the threads would increase friction, which would provide less pulling force at a given torque. So, I would clean the threads without lubricating them.
How great is the danger from lubricating the threads and torquing the nut to the dry torque spec? I agree that there is danger, but I am not sure how dangerous it may be. From the automotive engineers point of view, these stuff must be designed to withstand fair amount of abuse. Until 10 or 20 years ago, not many people used torque wrenches to tighten wheel lugs. They just tightened them with impact wrenches. I am hesitant to guess what the possible torque that might be, but greater than 150 ft-lb is not unimaginable, when most cars call for 90 ft-lb to 120 ft-lb for the lug nuts. So, if GEORGESANJOSE lubricates the threads (lightly as he says) and torques them, the pulling force on the studs may be equivalent to dry torquing it to 120ft-lb to 130ft-lb, which would definitely too much according to the manual, but I would guess it probably is within the design spec of the manufacturer. I am not saying I agree with GEORGESANJOE in lubricating the threds. But what I am saying is that it probably is safe. Well, he hasn’t had any trouble so far. I guess the problem is in not knowing all the facts. Car manufacturer will not tell you that 100 ft-lb is the ideal torque for the wheels, but they are perfectly safe to torque to 150 ft-lb. They will only tell you what the specified torque is. So, GEORGESANJOSE is treading unknown territory when he lubricates the threads, then torques it to dry spec.
About rust on the wheel studs. I recently moved from the west coast where rust is unheard of. There, I had never experienced any stubborn lug nuts or rusted nuts. Only when I moved to Boston, I experienced rusted wheel studs. I bought a set of winter tires, so this is my second time taking all the wheels off and putting another set on. Like GEORGESANJOSE said, I torqued all the lug nuts, but when I tried to take them off a few months later, some of them were extremely tight… In fact, one of them broke off.
In conclusion, I agree with GEORGESANJOSE’s method of putting on the lug nuts, except lubricating them. I think the owner’s manual also calls for checking the torque after driving a few miles, especially for aluminum wheels. I recheck the wheel lug nut torque the next day (after a round trip commute). Last fall, a couple out of the 16 lug nuts tightened a little more the next day. So, I think it is extremely important to check the tightness of the lug nuts after the initial installation.