Monthly Archives: August 2016

Change Your Oil Tips

If you are one of the many people who let a windshield reminder sticker govern when they get an oil change, here’s our advice to you: Drop that habit. Instead, follow the automaker’s recommended service intervals. In many modern cars, your best bet is to rely on the vehicle’s oil life monitoring system to let you know when it’s time for a change.

Let the Manual Guide You
Oil change information is in the maintenance chapter of your owner’s manual. If for some reason you’ve misplaced your owner’s manual, many automakers have put their manuals online. You can also search our Edmunds Maintenance Schedules. We have an extensive maintenance database on vehicles dating back to l980.

In many instances, you’ll find that the owner’s manual lists two service schedules. These are based on “normal” and “severe” or “special” driving conditions. Read the descriptions carefully to see which schedule reflects how you drive. In our experience, the vast majority of people fall into the normal schedule.

Trust Your Oil Life Monitor
In recent years, a number of automakers have installed oil life monitors of varying complexity in their vehicles. The more basic versions are more maintenance minders than actual systems. They’re based on mileage, and switch on a maintenance light when the vehicle hits a predetermined mileage range.

The more advanced oil life monitors, on the other hand, constantly take information from numerous sensors throughout the vehicle and then use a complex algorithm to predict the life of your oil. Based on your driving conditions and habits, the frequency of your oil changes can vary.

These systems take the guesswork out of knowing when your next service is due. Just drive as you normally would and wait until the maintenance light comes on. You’ll be surprised to see how far a vehicle can go between oil changes. The hardest part is not letting your preconceived notions of oil change intervals second-guess the monitor.

It’s also important to note that these systems are calibrated to work with the factory-recommended oil. They aren’t sophisticated enough to recognize that you’ve upgraded to another blend, so save your money and stick to the factory fill.

Use the Time Estimate
If you have a weekend car or put very low miles on your vehicle, you’ll have to change your maintenance strategy a bit. Robert Sutherland, principal scientist at Pennzoil Passenger Car Engine Lubricants, says that over time, oil becomes contaminated by gases that blow by the pistons, and the longer the oil sits with that contamination, the more it degrades.

Monitoring Systems Of Car Oil

Until recently, the question of when to change your oil was usually answered by your local garage, which had a vested interest in servicing your car every 3,000 miles. Your alternative was to crack the owner’s manual to see whether your driving habits fell into the “severe” or “normal” category. And then you’d let the listed interval be your frequency guide.

But increasingly, the change-interval question is being answered by a vehicle’s oil life monitoring system, which signals the driver through the instrument panel. This alert usually arrives anywhere between 5,000 and 8,000 miles.

So how does the system know when it’s time for a change? Electronic sensors throughout the drivetrain send information about engine revolutions, temperature and driving time to the car’s computer. The data is run through a mathematical algorithm that predicts when the oil will begin to degrade. The light comes on well in advance, giving the owner time to get the car serviced.

Oil life monitoring systems have been around for several decades. They were introduced in General Motors vehicles in the late 1980s and have been phased in slowly, said Matt Snider, project engineer in GM’s Fuels and Lubricants Group. “We are very confident in the accuracy of the system,” he said. The average recommendation from the system for GM vehicles is 8,500 miles, Snider said. He said that the longest oil change interval he was personally aware of was 17,000 miles in a colleague’s car. For 2010 vehicles, 14 of 35 manufacturers use oil life monitoring systems.

Real-World Evidence
The oil life monitoring system in a 2007 Honda Fit Sport owned by an Edmunds.com editor signaled for an oil change at 5,500 miles, due to a lot of around-town driving. Later, under highway conditions, the system (which Honda calls a “maintenance minder”) came on at 7,600 miles. Clearly, the system had detected different driving conditions and adjusted accordingly.

When we had the oil changed, we captured a sample and sent it to Blackstone Laboratories. Showing the conservative nature of the oil life sensors, the analysis showed the oil had at least 2,000 miles of life left in it.

A long-term 2008 Pontiac G8 GT driven by Edmunds went 13,000 miles before the monitoring system indicated the need for an oil change. We also sent a sample of that oil to a lab for analysis. The result: The oil could actually have safely delivered at least another 2,000 miles of service. “With an oil life system, we can use the software to tailor an oil drain interval to the behavior of a certain customer,” Snider said.

Freed From the Schedules
Perhaps the best thing about oil life monitoring systems is that they free car owners from the confusing exercise of slotting themselves in the normal or severe driving schedules listed in the owner’s manual. Severe conditions are described differently by various carmakers, but some “severe” conditions that they frequently cite are driving in stop-and-go traffic, towing, excessive idling and driving in the mountains.

In many cases, quick-oil-change outlets and dealerships’ service departments encourage frequent oil changes by claiming that every driver falls in the severe category. This begs the question: Why have a normal category at all? Oil life monitoring systems put an end to the debate by reacting to how you actually drive.

Car Oxygen Sensor Repair Tips

images-53If your car’s “Check Engine” light is glaring at you, it’s probably because the oxygen sensor is malfunctioning. That’s right, the oxygen sensor. It’s a little device that’s a mystery for most drivers but its misbehavior is the problem that most commonly triggers a Check Engine light, according to CarMD.com, which sells an automotive diagnostic tool and provides repair information. The oxygen sensor unseats the formerly most common Check Engine light culprit: a loose gas cap. There are fewer reports of that problem because savvy motorists have learned to fix it themselves and consumers now buy new cars with capless gas tanks.

But don’t despair. Replacing your car oxygen sensor will keep you from wasting money by burning extra gas, and the repair isn’t horribly expensive. We know this firsthand. We had to replace the O2 sensor on our 1996 Lexus ES 300, the subject of our Debt-Free Car project, and it wasn’t as much of a hassle or expense as we had feared.

After the dreaded Check Engine light appeared in our Lexus, we plugged the CarMD device into the car’s computer to read the error code. In our case, the code was P0135, which meant that the oxygen sensor in “bank 1” was malfunctioning. It was surprising to learn that something was wrong with the car, since it still seemed to be running fine.

Even though a car seems to be behaving normally, a faulty oxygen sensor will cause the engine to start “gulping down gas,” says Kristin Brocoff, director of corporate communications for CarMD.com. She says this problem can cause up to a 40 percent reduction in fuel economy. Sure enough, when we checked our fuel record for the driving we did while the Check Engine light was on, our mpg had taken a hit.

The oxygen sensor, developed in the early 1980s, is an essential part of the car’s emissions control system, says John Nielsen, director of engineering and repair for the American Automobile Association (AAA). The sensor is about the size and shape of a spark plug and protrudes into the car engine’s exhaust stream. It determines if there is a lot or a little oxygen in the exhaust, so the engine can make adjustments to the amount of fuel being used in the engine to run at maximum efficiency.

Oxygen sensors in older cars fail for a variety of reasons, according to Bosch, a leading manufacturer of auto components. In some cases, sensors are fouled by gasoline additives or oil from worn engines. Newer oxygen sensors can last 100,000 miles if conditions are right, but often problems occur sooner.

After we plugged CarMD’s diagnostic device into the Lexus’ onboard computer port, we connected it to our desktop computer. It accessed a database of information about this engine code and how to have it repaired. Among other things, the report included an average estimate just to buy a new oxygen sensor: $168.82.

At the first sight of a Check Engine light, most owners of new cars that are still under the factory warranty would simply make a beeline for the dealership’s service bay. But car owners on a budget might want to go the do-it-yourself diagnosis route to save money. By using the CarMD device, or any engine code reader, drivers can learn what the problem is, and the skill level required to fix it, before attempting the task.

Modern cars have two to four oxygen sensors, Nielsen says. A V6 engine, such as the one in our Lexus, has one sensor in each exhaust manifold and one after the catalytic converter. The sensors simply screw into place, but reaching them can be a problem for do-it-yourselfers. Additionally, since the exhaust subjects the sensor to extreme heat, it can “seize” (become frozen in place) and be tough to unscrew. A new sensor comes with anti-seize compound to apply to the threads, but the compound should never be put on the sensor itself.