Business

Engine oil consumption: How much is too much?

February 8, 2011 at 8:20PM

Q My daughter shopped, purchased and financed her first vehicle on her own. It's a 2000 Nissan Pathfinder. She bought a warranty through the dealer. No complaints, except this rig goes through a quart of oil every 500 miles. The warranty folks don't want to spend any money because nothing is broken. Is there any way to resolve this short of just letting the engine run out of oil and seize up? I'm not sure they would honor the warranty in that case anyway, and it would be pretty irresponsible.

A I agree that letting the engine run out of oil and fail is a bad plan, but I do understand the frustration. You didn't mention how many miles are on this 10-plus-year-old vehicle nor the specifics of warranty coverage, but the typical industry standard for oil consumption is about 1,000 miles per quart. Most warranty coverage would require a specific oil consumption test to determine the exact level of oil use. If that level exceeded manufacturer's specifications, warranty coverage for repair would likely apply.

Again, I don't know the specifics of the warranty on this vehicle, so I suggest you have her read the warranty carefully and if necessary ask for legal help from an attorney or the state attorney general's office.

In the meantime, changing to slightly heavier oil (10W rather than 5W), lowering oil operating temperatures by adding an additional oil cooler or switching to synthetic oil. Trying an oil additive or engine flush may improve oil consumption to an acceptable level. Good luck!

Q My 2002 Impala has intermittent electrical problems. The message center indicates "security," "service engine soon" and "battery." During this time, the radio does not work and the air conditioning works only by repeatedly turning it off and on. The battery was replaced last month, but the problem has become more frequent.

A The good news is that an intermittent electrical problem rarely means a component failure. The bad news is that the very nature of most intermittent electrical problems is the difficulty pinpointing the cause. In your case, there might be a specific answer. My Alldata automotive database pulled up GM service bulletin 00-06-04-049B, dated December 2003, that identifies electrical issues similar to yours and directs technicians to check for the "engine wiring harness chafing against the mounting ring on the A/C accumulator."

Q Could you shed some light on a problem with my dad's '03 Chevy Blazer V6 with 125,000 miles? About six months ago, the "service engine soon" light came on steady. The P1153 code (HO2S B2 S1) was the current fault displayed. I replaced the oxygen sensor with an original-equipment part, and the light stayed out for about three months. Now, the "service engine" light is illuminated again, with the same P1153 code displayed. Is there a service bulletin on that vehicle for this problem?

A No, but this situation provides a good opportunity for all of us to understand a bit more about modern on-board diagnostic systems. The diagnostic trouble code P1153 indicates that this heated oxygen sensor's rich-lean-rich transitions are less than the calibrated value. It does not necessarily mean the sensor is faulty. The engine may be operating too rich or too lean, or the sensor may have become contaminated from excess oil, fuel or coolant. The fault code could also indicate a harness or connector issue for the sensor.

Having replaced the sensor once, the next step is to connect a scan tool to monitor engine operating temperature and performance and test the sensor's dynamic performance.

ones that have come into our shop during the past decade) have had a tendency to burn oil. Their engines burn through more oil between oil changes than we're comfortable with. And for that reason, we're going to suggest that you change the synthetic oil every 5,000 miles in this particular car. Tom: It might not ultimately prevent your engine from burning oil, since we don't know exactly what's causing the oil burning. But it might help. It certainly can't hurt. Ray: And it doesn't have to screw up your "free scheduled maintenance" agreement. You simply tell the dealer that you're willing to pay for an extra oil change in between the scheduled oil changes. You pay for an extra, unscheduled one now, at 6,500 miles, and then they'll change it again for you for free at 10,000 miles. Tom: It's true that if you do this, it'll cost you 80 bucks once a year or so. But it's cheap insurance for your engine. You can think of it as honoring your late husband's wishes. And helping your poor VW dealer make his boat payments. Have a good trip, Bonnie. Q I love your show and column, and am a longtime listener and reader. After all these years, I finally have a question for you. I know you guys recommend having a used car inspected by a trusted mechanic prior to buying it. But what about buying one from a dealer? I'm considering the purchase of a 2008 Audi TT under one of those certified used car programs where the cars have low mileage and the dealer does a 123-point inspection. Do you think it's wise to have another mechanic check out the car first? -- BARRY Ray: We do. Because it may be the 124th point that ends up costing you money later on. Tom: Buying a car that's part of a manufacturer's certified pre-owned program definitely increases your chances of getting a nice used car. Presumably, they screen for mileage, accidents and major problems. And that's all great. Ray: But even if they do a thorough screening, the dealer's primary interest is in selling you the car and getting the maximum possible price for it. In our opinion, it's good to have someone who is entirely on your side in this transaction. That would be a mechanic you hire to inspect the car and report to you about what he finds. Tom: Even if he doesn't find evidence of an accident or a major mechanical problem, your own mechanic often can give you some items to negotiate over. For instance, he may tell you that the tires are fine, but they're only good for another 10,000 miles. In that case, maybe you can get the dealer to throw in a new set of tires. Ray: If your mechanic tells you that the brake discs are starting to warp, you can ask the dealer to replace those before you buy the car, rather than coming back in six months and paying for them yourself. Tom: And even if your mechanic finds nothing wrong, and says, "This is the finest 2008 Audi TT I've ever seen in my life," you'll be able to make the purchase with peace of mind, knowing that the car is exactly as represented when you drive off the dealer's lot. Ray: And when you're spending tens of thousands of dollars on a car, we think $100, even if it's only for peace of mind, is always money well spent. Enjoy your TT, Barry. E-mail Click and Clack (Tom and Ray Magliozzi) from the Car Talk website at www.cartalk.com.