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Automania/Repair & Maintenance


by Bob Hagin

Q. I have a '97 Toyota Tacoma and a '99 Toyota 4Runner both with V6 engines. The owner's manual calls for dual electrode non-platinum spark plugs only, while the aftermarket auto parts stores show single electrode plugs in their applications charts. Would there be any risks in using the single electrode plugs or the higher-end platinum plugs?
B.O. Yucaipa, CA

A. My source of Toyota information tells me that during the '80s, Toyota made a small sedan model the had dual-electrode spark plugs as the original equipment and recommended replacement. The company had some troubles with burned pistons and collapsed rings, and the factory engineers laid the problem on the replacement of the dual-tip plugs with single-electrode units. Now many Toyota mechanics use only factory recommended plugs rather than experiment with others. I don't think that Toyota has a vested interest in dual-electrode spark plugs so if the prices are comparable, I'd stick with the factory recommendations.

Q. A local repair shop told me that refiners recently began saving money when they eliminated a certain moisture-preventing additive from their motor oils. Result: In our damp Northwest climate, engines that are not run regularly can build up excessive amounts of sludge, eventually blocking oil passages and causing severe damage. The shop owner had this happen to his Cherokee. Recommended solutions: Change oil and filter every three months regardless of mileage or convert to synthetic oils or use oils that are specified for diesel engines and still contain this additive. Is the shop owner correct? I can imagine a lot of problems for those who are unaware of this and who have cars that are not used more than once or twice a week. I've seen no mention of this in any newspaper or auto publication. To me, this is a major change with wide impact if the asserted consequences are true.
G.G. Bellevue, WA

A. While I have no personal fondness for the oil companies (the one I live next door to has an explosion once or twice a year that rattles my windows and threatens my environment), I can't imagine any of them changing their formula to the extent where is wouldn't conform to Society of Automotive Engineers (SAE) and American Petroleum Institute (API) specifications. Moisture (water) in motor oil gets pretty hot even after an engine runs for a very short time, then turns into water vapor and other byproducts that are sucked into the engine, burned and sent out the tail pipe. How hard an engine is run is more of a determinant of oil-change frequency than how many times its run per week. I'd also want to see more impartial data than a single example. Oil can be tested for contaminants at testing labs usually found close to major airports. Changing to a synthetic motor oil in a high-mileage vehicle runs the risk of having it "wash" contaminant buildup off the interior of an engine and then the loosen residue may clog up the lubrication system.

Q. We have a '98 Dodge Dakota SLT with a V6 engine, automatic transmission and a non-slip rear end. Since new, it's had a whine at 35 to 50 mph. The dealer replaced the ring and pinion once and then the entire rear end. The noise remains. A factory rep drove it and told me that all rear ends have a noise but you don't hear it in a car because of insulation. The dealer says he can't do more without authorization.
D.R. Chesapeake, VA

A. Remember that a factory rep's job is to keep warrenty rates as low as possible. Rear ends don't whine unless they're designed or assembled wrong and it's kind of an exacting art to get them right. My standard response to a problem like yours is to try another truck exactly like yours to see if "...they all do it" which is a common response to nagging problems like yours.


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