Q: I have a 2010 Honda Accord with 110,000 miles on it. I am going to replace the spark plugs. The recommended iridium spark plugs, NGK or Denso, are very expensive. Some online prices for the same spark plug are almost half the cost. There are numerous articles on the internet warning of fake spark plugs. Are these cheap spark plugs OK to use, and how can one tell the difference between the fake spark plugs and the real ones?

— W.N., Woodbury, Minn.

A: Cheap auto parts are often counterfeit. Not only may they fail to work properly, buying counterfeit parts harms the true manufacturers’ income and reputation. It is nearly impossible to tell the difference by simply looking at the item or the box so buy your auto parts from a reputable parts store, which you can also do online.

Q: I have a 2009 Toyota Rav4 with 166,000 miles on it. My independent garage of 25+ years closed. I went to a highly recommended shop. They changed the oil but couldn't get the filter off. They said that they would have to break something (housing?) to get it off. They did not have the new parts. They said I could drive it another 5,000 miles with the old filter and when I come back, they will order the new parts ahead of time to repair and replace the filter. I am nervous about driving with the old filter for 5,000 more miles. Should I just go to another shop and start over again?

— N.P., Ramsey, Minn.

A: I am unclear on what part they need, but it is not uncommon for the cap to need replacement. If so, they are readily available from most auto parts stores as well as a Toyota dealer. As for driving another 5,000 miles, you should be fine. But chances are that the shop will locate a new part well before that. You should try another shop as soon as convenient. Maybe they will be able to replace your filter. No need to get another oil change, though.

Q: Recently we were driving our 2010 Hyundai Tucson in stop-and-go traffic. Each time that we stopped, the air coming out the register in the dashboard while cool was not as cool as it usually is. When traffic started moving, at 30 mph the air came out much cooler. I looked through the grill at the condenser and it was heavily caked with dirt and dead bugs. Using a pressure nozzle, I rinsed the condenser thoroughly and the output air temperature came down. Saved a trip to the shop.

— S.B., Las Vegas

A: Good catch and often overlooked by motorists living in dusty areas. Not only is the airflow across the A/C condenser blocked, but the radiator sitting behind it suffers too.

Q: I have a 2011 Ford Focus and I am having a hard time locating the cabin air filter. Does it have one or not? It has never been changed and my A/C doesn't blow very cold. Do you think a bad cabin filter could be the cause?

— G.B., Roseville Minn.

A: If you have normal airflow from the vents when you are not using the air conditioner, the cabin air filter is not causing a restriction. The filter on the 2011-2018 Focus is located on the left side of the passenger foot well. You must first remove a panel below the glove box to access the cover for the filter. It is not a simple job.

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(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.)