Q. The speed limit in our retirement area is 25 mph. With the cruise control set or not, my new 2018 Equinox surges back and forth like it's trying to shift to a lower speed. I took it back to the dealer, and they could not find any thing wrong with it. I went for a ride with their tech rep, and he was able to duplicate it the problem. They told me there is no cure for it. I cannot drive the car like this, and I find that this problem is not only mine. The dealer people were great in trying to solve it. How can I get this fixed?
A. I chatted with Mr. G by phone to get a bit more information about his concern. His rather huge retirement facility has lengthy sections of 25 mph roadway and strict speed enforcement, so it's understandable he's bothered by poor drivability at this particular speed. I recommended that he drive the Equinox at the problem speed and try manually selecting a differing gear and observe any changes in symptom. Also, he might try very softly applying his left foot to the brake pedal as he continues to hold speed and check again for a change in symptom. This would cause the transmission's torque converter clutch (TCC) to release, if it were engaged. My hunch is that, to maximize fuel economy, the PCM (powertrain control module) may be engaging the TCC at a painfully low vehicle speed. The effect is similar to driving a stick shift car at too low a speed for the gear selected.
As sharp as his dealer's top gun troubleshooter may be, it would help to call Chevy's customer service folks and request a field engineer come to witness the concern. If the surge seems to be by design and enough folks complain about it, perhaps GM might come up with a flash (software update) that could mitigate the concern. Many moons back I was a dealer tech with an unhappy customer complaining of an occasional engine performance jolt. I was able to capture a scan data movie showing the A/C clutch engaging at unfortunately the same exact time as a transmission TCC engagement. Our customer was thrilled to become the guinea pig for a new calibration attempt that ultimately solved the quirk.
Q. My new 2017 Honda Accord Hybrid is using 5-20W synthetic oil per the manufacturer's recommendation. Same thing with my neighbor's new Camry. I was told using 5-20W synthetic oil is part of the reasons to achieve high gas mileage. If the car is using 5-20W oil, does that mean I better avoid driving to Arizona in hot summer days? I have a 2005 Nissan Titan truck. If I switch over to use 5-20W synthetic oil, would I get a better gas mileage?
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A. This can be a controversial subject! Some oil companies and old timer techs say go up a click to 0W-30 for high ambient temps. Honda recommends 0W-20 oil regardless of the ambient temperature. This makes sense to me as the vehicle's cooling system should maintain about the same operating temperature during either warm or hot weather. Honda recently came out with an even thinner 0W-16 synthetic oil that can be used in the 2017 Accord hybrid for even better efficiency and friction reduction! Maybe skip this one for Arizon. It's important to stick with what the manufacturer recommends because the engine's internal part clearances and oil-fed circuits such as variable valve timing systems require clean oil and the correct oil viscosity. Stick with the recommended 5W-30 for the Titan!
Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose, Calif. Readers may send him email at email@example.com; he cannot make personal replies.
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