Driving an SUV in ECO Mode

Dear Doctor: I recently purchased a 2016 Jeep Grand Cherokee. It has an “economy fuel mode” option, but I’m not certain if it should be used or not. The manual states the following: When the Fuel Economy (ECO) Mode is engaged, the vehicle control systems will change the following: “The transmission will upshift sooner and downshift later; The torque converter clutch may engage at lower engine speeds and remain on longer; and the overall driving performance will be more conservative.” I don’t know if it is wise to use this ECO mode all the time. Does it put too much stress on the transmission?


Dear Sonya: The ECO mode is designed for conservative driving for motorists who are very light on the gas pedal. You do not need to be concerned about operating a vehicle in the ECO mode. My wife keeps her car in the ECO mode all of the time, but when I drive her car I turn it off. It’s just my personal preference not to operate a car in ECO mode.

Dear Doctor: I have a 2005 Chrysler Town & Country minivan with 120,000. Lately my fuel economy has dropped to only 14 miles per gallon. I used to get much better mileage. The minivan runs well, has plenty of pep, there are no leaks and no “check engine” light is on. What’s causing this drop in fuel economy?


Dear Vincent: Gas mileage is impacted by many conditions, including tire air pressure, tire tread design, the transmission shifting into high gear and overdrive, air filter condition, oxygen sensor operation, and the engine reaching full operating temperature. A good technician will connect a professional scan tool and take your minivan for a road test to observe all computer information being fed to the scan tool. The technician will especially look at the 02 sensor speed, engine temperature and transmission shifting. A lazy oxygen sensor and thermostat operation will also effect gas mileage.

Dear Doctor: Our household has two Toyota Camry four-cylinder vehicles that use regular octane gasoline. Would it be a waste of money to occasionally fill the tanks with premium fuel?


Dear Marty: There are mixed professional opinions on this matter, however, I personally use premium unleaded in my vehicles — and under hard acceleration I can feel the difference with the higher octane. Premium gasoline burns hotter, and cleaner, plus it has different additive packages mixed into it. I like the idea of filling the tank with premium before a long trip on the highway. The long drive with premium gas will actually help clean off carbon deposits. And before I store yard equipment for the winter I use the fuel from my local hardware store; it’s expensive but I’ve never had a carburetor problem after the equipment sits for six months.

Dear Doctor: My 2017 Ram 2500 diesel pickup truck has a problem with the automatic lock on the tailgate, which is supposed to automatically lock whenever the transmission is shifted into drive. Generally it does so, but once in a while it does not automatically lock and the tailgate falls open. This problem has already What should I do?


Dear David: My first concern in the tailgate opening by itself. This tells me the tailgate latch did not latch fully, and this will cause the automatic power lock not to lock. I recommend you find a technician who can determine the reason why the latch is not locking the tailgate.

Dear Doctor: I have a follow-up question regarding the owner of a 2013 Lexus RX 350 with only 21,000 miles and the service advisor recommending a brake fluid flush. Brake fluid is hydroscopic and Acura / Honda recommends this service every three years regardless of mileage. Although other automakers don’t recommend this service, most auto technicians I am familiar with do. For a 2013 RDX 350 worth well in excess of $20,000, don’t you think this appears to be a reasonable service expense after five years?


Dear Barnett: Yes, to clarify, at five years of age, regardless of mileage, the brake fluid should be changed. The five-year interval should be the time limit on brake fluid replacement. Brake fluid does attract moisture. It’s advisable to follow the manufacturer requirements for brake fluid changing. This includes never intermixing brake fluid types and checking the owner’s manual for the specific type for the vehicle. Not all brake fluids are the same among carmakers.

Junior Damato is an ASE-certified Master Technician.

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