Q. I have a Lexus RX 350, and I suspect the sunroof drains are clogged, causing water to back up into the vehicle. I have read about using compressed air (I have a small air compressor) to clean the drains, but I have also read that using too much air pressure could damage them. Any suggestions?

A. When I check sunroof drains, I typically use an aerosol air duster, the type used for cleaning computer keyboards and other electronics. The air pressure is usually sufficient to clear light debris, and the nozzle straw fits nicely into the drain openings without the risk associated with shop air. Another option is to use weed trimmer line. The flexible trimmer line makes an excellent “snake” for gently pushing out debris without risking damage to the drain tubes. Excessive compressed air pressure can sometimes disconnect a drain hose inside the vehicle, creating a leak that is more difficult to repair than the original clog.

Q. I have two vehicles, a 2019 Subaru and a 2020 Toyota RAV4. I do my own oil changes. The Subaru requires 0W-20 oil, and the Toyota is specified for 0W-16 oil. I got a bit confused and used 0W-20 oil in the Toyota. Am I causing any harm to the engine?

A. You are correct that the Subaru requires 0W-20 oil and the Toyota is specified for 0W-16 oil. When I looked up the specifications, I found something interesting. The same engine used in the RAV4 in some markets, including Mexico, is approved for oil viscosities ranging from 0W-16 to 10W-30, provided the oil meets the appropriate SM/SN API (American Petroleum Institute) service classification. Based on that........

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