Q: A blinking check engine light came on while setting a four cylinder misfire code. I suspected a bad ignition coil, which I replaced. I have cleared the codes and the car is running fine. I was able to find an auto parts store open late and luckily the coil was in front of the engine and not in the back. A rear coil will likely fail in the middle of winter and at temperatures below 20 ° C. I would like to replace the rear spools and I can get a better branded spool for less. Is it okay to mix coils from different manufacturers?

JD, Chicago

A: Yes. Each manufacturer must manufacture their parts according to the specifications of the original equipment. Having said that, I prefer to stick with parts from the same company.

Q: My normal gas station (a Sam’s Club) has one-way traffic at its pumping islands. I have noticed that there is always a row with multiple cars for vehicles with gas caps on the left side, but rarely a row for vehicles with gas caps on the right side. Just a rough estimate, but I’d say about 80% of vehicles on the road have gas caps on the left side. Right side versus left side: How is this choice made during the design process? Is there a statistic for the percentage of vehicles on the road with gas caps on the left versus the right?

MM, Springfield, Illinois.

A: It seems there are stats for everything, although baseball seems to have the most. If there are any statistics on gas caps, I haven’t found any. My hunch is that design engineers look for the most convenient location with the shortest distance between the tank and the intake, which is usually indicated on the dashboard with an arrow next to the l icon. ‘gasoline.

Q: I bought a new 2021 Tucson this spring. My first new car in 17 years! I love it but I have a question. We went to two dealerships and both salespeople said the oil change should be done every 3,750 miles. I’ve taken my car twice now, at 3,750 and 7,500. After-sales service tells me I only need to come every 8,000 miles. I have followed the 3,000 mile / 3 month oil change guidelines and tire rotation every six months for over 40 years. I don’t want to void the warranty on my new car. Who do I believe?

Saskatchewan, Minneapolis

A: Trust your owner’s manual, it’s the car’s bible. By reading the maintenance section, you will find the service interval blessed by the automaker. You will change the oil and filter once a year or every 7,500 miles. It seems like a sin to waste money on unnecessarily frequent oil changes.

Q: You recently wrote that using cruise control results in better gas mileage. We have a 2018 RAV 4 and have driven from our old residence in Virginia to Illinois several times. On one of these trips I used cruise control whenever possible, and on another identical trip I only used the pedal, which generated an extra 2 mpg when cruising. I suspect the cause is the extra braking for slower vehicles and unnecessary gear changes on inclines.

JC, Mokena, Ill.

A: Not everyone can fine tune the throttle like you. When you lift your foot to brake, you close the accelerator. Riding to a stop helps, as does smooth acceleration from a standstill instead of coming back to 55 mph as quickly as possible.

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