The Car Doctor

Best speed for fuel economy, power steering fluid, copying keys

By John Paul, AAA Car Doctor
May 29, 2008

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Q. I've heard the general rule that traveling on a highway at 55 mph is the speed at which your vehicle runs the most fuel-efficient. I've also heard that a performance engine has a higher speed of efficiency than a base engine model. If so, what would be the best speed to travel to get maximum efficiency from a supercharged or turbocharged engine, in your opinion?

A. The performance from a supercharged engine may be different than a normally aspirated engine - although power and fuel efficiency are not always equal. In general, a speed of 55-65 mph is optimum for fuel economy, for two major reasons. At this speed the engine is usually running at 1,800-2,400 rpm - the most efficient for the engine. The second reason involves aerodynamics. At speeds over 65 mph you are using more energy to push the vehicle through the air. This energy use translates into fuel use.

Q. I installed a new rack and pinion steering gear and power steering pump on my Ford Aerostar. When adding fluid, what type is recommended? I noticed red fluid in the rack and pinion gear, and clear fluid in the steering pump. Do I need to flush the system before I continue with one type of fluid?

A. The Ford Aerostar uses Ford type-F automatic transmission fluid. It wouldn't hurt to flush out the assembly fluid when refilling the system. Once the system is full, start the van and turn the steering wheel all the way to the left, and then, all the way to the right. Repeat this a couple of times: this will bleed any air out of the system. Once completed, re-check the fluid and check for any leaks.

Q. I own a 2002 Subaru Outback wagon that we purchased used from a dealer three years ago. We have the original key and a spare key that were both given to us at the time we purchased the car. I misplaced my set of keys with the original key on it, and tried to get another copy made from the spare key. I tried several hardware stores and even went to a Subaru dealership. Each time they made a copy from my spare key, it would not work in the car. The key would go in, but wouldn't turn. This even happened at the dealership. The hardware stores blamed it on a worn spare key, and said I needed to go to a Subaru dealer. I did, and the dealership also looked up the year and make of my Subaru, and tried to make a key according to some information they had at the dealership--they looked up something in the computer. But they still couldn't make a key that would work. Fortunately, I have since found my set of keys with the original key, but this still puzzles me. What would be the reason for this? I'm just hoping I don't lose my keys again, because everyone seemed to be stumped by this problem. Do you have any suggestions?

A. It is possible the spare key was worn, but I'm not sure why a key made with the factory key code didn't work, unless the ignition was replaced. At this point, I would make at least one copy based on the original key and see how that works.

Q. My father in-law recently had his 45,000 mile check up on his 2003 Camry at the dealership where he purchased his car. All service to the car has been done by the same dealership. On this occasion, he received a call from the Service Manager because he needed a new oil pan. The Service Manager said the drain plug threads had pulled out with the drain plug. He further stated that this is an occasional problem that should be expected since the car was almost five years old even though it has low miles - 45,000. I called the Service Manager and requested the old pan and picked it up. The threads are worn down smooth. Is this the case, as the Service Manager states, or could it be the certified Toyota technician stripped the threads? They billed him for the pan but waived the labor charge. Your thoughts would be greatly appreciated.

A. If the oil drain plug has been properly installed at each oil change, this shouldn't have happened. In almost every case, the oil pan threads become damaged due to over-tightening by the technician performing the service.

Q. I own a 2001 Jeep Wrangler 4.0L, and I bought it new. A recurring problem has been the climate control panel, particularly the fan speed switch. Eventually certain fan speed levels stop working, and before long the fan speed switch stops working altogether. This has happened three times, and each time the dealership's remedy was to replace the control panel and, in one case, rewire the climate control system. Now that this vehicle is far out of warranty, I am not eager to continue treating the symptoms when the cause has clearly gone unaddressed. Right now, only two fan speed levels work in my Jeep, and it's just a matter of time until wires start melting behind the dash, and I'm looking at a four-figure repair bill. What should I do?

A. This is a fairly common problem. Once the connectors start to come loose, they start to heat up and cause this problem. Repairing the wiring and splicing in a better quality connector usually fixes the problem. At the same time, take a look at the resistor for the fan.