Q: I've got a 2005 Honda Accord V-6 with only 78,000 miles on it. I have changed the oil religiously according to the owner's manual from the day I purchased it new. Within this last year it has developed a knocking sound that is fairly loud when the engine is cold but diminishes greatly once the engine has warmed up. I think that it is piston slap. This seems to be fairly common with this type of car. How can this be fixed? Are there any oil additives that are safe and will help? One article I read said that the only sure way to get rid of it is to replace the engine.
B.W., Montgomery, Ill.
A: If the noise is indeed piston slap then this is nothing to be alarmed about. There is certainly no need to replace the engine. The bottoms of the pistons (skirts) strike the sides of the cylinders as the pistons reverse direction. After warm-up, they fit snugly. Additives are neither necessary nor helpful.
Q: In the six years that I've had my 2006 Lexus RX350, the battery/alternator has lost power approximately two to three times per year, resulting in an emergency call and jump-start. The battery has been replaced twice. That's not the answer to this problem. I usually drive locally. However, even in good weather, after driving 45 minutes on the expressway, this car wouldn't start an hour later when I tried to go home. The Lexus service department cannot determine the root cause and suggests that I buy a battery tender for daily plug-in use. That shouldn't be the answer. I haven't taken it elsewhere. Should I? Do you have any suggestions other than selling the car?
P.A., Glen Ellyn, Ill.
A: A battery maintainer, such as a Battery Tender, is a good solution, especially for those who do not regularly fully recharge their batteries by driving. Your frequent short trips keep depleting the battery, which is then left in a low state. If you feel that your Lexus dealer is giving you the brush-off, find another shop and ask for the charging system printout after it performs its tests. Replacing the vehicle will probably result in a similar problem but with a different car.
Q: I have a 2013 GMC Sierra that requires Dexos oil. The truck is new to me, and I have never had vehicles that use oil monitors. In the past, I changed the oil every 3,500 miles, but now the interval is up to nearly 9,000 miles. The GMC manual has no recommendations on what oil filter to use. I have always been a die-hard Purolator One fan and have used them in all my vehicles. Can the medium for these standard filters support the long intervals of the newer synthetic oils?
J.P., Chicago
A: General Motors' latest specification for motor oil has the trademarked name dexos. (Yes, dexos with a lowercase "d.") Most motor oil brands meet this spec and note such on the bottle. Others may meet the spec but refuse to pay the fee to state it on their product. Oil life monitors have been around long enough to prove they are reliable. Your choice of oil filter brand is up to you.
Bob Weber is a writer and mechanic who became an ASE-certified Master Automobile Technician in 1976. He maintains this status by seeking certification every five years. Weber's work appears in professional trade magazines and other consumer publications. His writing also appears in automotive trade publications, Consumer Guide and Consumers Digest. Send automotive questions along with name and town to motormouth.trib@verizon.net.