Clean oil keeps engine flowing, lowers gas mileage

Ask the Auto Doctor

DEAR DOCTOR: My wife drives a 2012 Toyota Highlander with 55,000 miles, and I drive a 2016 Highlander with 35,000 miles. Synthetic oil has been used in both vehicles since they were new, including changing the oil / filter every 10,000 miles. Neither car is subject to unusual climate or road conditions. I expect we’ll keep both Highlanders for another three to four years, or until 100,000 miles. As these cars age and the mileage increases, when is it advisable to step up the oil change frequency? Will the 10,000-mile interval be good enough?

–Leon

DEAR LEON: This is the most frequently asked question at my shop. Most customers say they are trading the car in three to four years, but I find they tend to keep the vehicles for another six-plus years. Oil flows through all of the electronically controlled valves that are computer connected which rely on clean flowing oil. Clean oil also improves gas mileage. The price of an oil change is cheap compared to an engine repair. As your vehicles increase in age and mileage, I would step it up to a semi-annual full-synthetic oil change.

DEAR DOCTOR: I have a question on the automatic stop / start technology. I own a 2016 Chevrolet Malibu. When I put it in low gear and upshift with the (+) it will not shut off. On the dash it will show “L6.” After I turn the key off, or put it in park, I have to do it again but while driving it operates normally. Have you had this experience?

— GT

Dear GT: What you’re doing is also what some other GM owners are doing. Most of the General Motor vehicles do not have a shut off switch for the automatic start / stop feature. Other manufacturer’s do offer an interrupt switch to cancel out the start / stop feature.

DEAR DOCTOR: I cannot increase the volume on my satellite radio and navigation system. My mechanic swapped the speakers, but there’s no improvement. While the radio itself works fine the Sat / Nav volume only goes from low to very low. Now what?

— Jon

DEAR JON: You did not mention the Year / Make / Model of your vehicle. So all I can tell you is that some late model vehicles may experience a fault code in the body control module. And your description sounds like a fault is in the main audio system. This requires sending out the unit to an electronic shop to be repaired.