Can he do right by his '96 Buick with 5W-30?

  • Article by: PAUL BRAND , Star Tribune
  • Updated: November 17, 2010 - 4:16 PM

Q I am a stickler for following owner's manuals and scheduled maintenance. My '98 Sable recommends 5W-30 oil. I just inherited a beautiful '96 Park Avenue, and it calls for 10W-30. Should I stick with the recommendations, or can I use 5W-30 in both cars?

A 5W-30 is approved for the Buick if ambient temperatures are below 60 degrees, but 10W-30 is recommended for ambient temperatures above zero degrees. Depending on where you live, 10W-30 for summer and 5W-30 for winter might be the right answer.

Q My 2002 Saturn L200 with 69,000 miles developed a loud rattling noise only at idle. When I accelerated slightly, the rattling would stop. It sounded like it was coming from the exhaust system. I suspected a piece of ceramic had broken off the catalytic converter. After several weeks, the noise went away.

Two weeks ago, the engine began to race going up inclines and seemed to lack power. The shop just phoned to say that the transmission failed because it overheated due to heat transfer from the overheated catalytic converter. Should I be looking for the root cause of the catalytic failure?

A First off, remember that the federally mandated emissions warranty specifically covers the catalytic converter for eight years or 80,000 miles. Depending on the original date of service, your car might still be covered by this warranty. Most catalytic converters fail because of excessively rich fuel-air mixtures causing the catalyst/oxidizing process to generate extremely high temperatures in the converter. Make sure the engine is reaching full operating temperature with normal air-fuel mixtures.

If the catalytic converter overheated from exhaust restriction, you'd have noticed a loss of power while driving, but not necessarily some type of slippage. It's possible the higher rpm occurred as the transmission downshifted due to the lack of engine power.

Second, since you could hear the rattle at idle, I suspect it was coming from a heat shield protecting the converter or exhaust system rather than the converter itself. Did your mechanic check to see if all heat shields are still in place?

Did the converter failure lead to the transmission failure? That's harder to say. I would have thought that you would have noticed symptoms of power loss long before any transmission damage would have occurred.

Q After many years of wishing and 19 years of working on my first car, a '54 Mercury Monterey, I've finally got it back to original condition. Could you bring us all up to date on putting a car away for the winter?

A After our wet, white and rude introduction to winter last weekend, I suppose it's time to park our favorite motorized toys for the season. In the past 30 years I've refined my winterizing efforts down to bare essentials.

• Park the vehicle with a full tank of nonoxygenated fuel with a fuel stabilizer such as SeaFoam.

• Charge and disconnect the battery. Or leave an automatic charger connected to battery, or connect a charger once per month.

• Toss dryer sheets into the cabin, trunk and engine compartment.

• Leave windows open a fraction.

If you so desire, you could also:

• Change oil and filter and make sure all maintenance is up to date.

• Lightly spray brake rotors/drums with Deep Creep to prevent rust.

• Fill tires with air about 5 pounds per square inch above normal to compensate for slight leaks.

• Cover, block and plug the air intake and exhaust to keep critters out.

• Clean, wax and cover vehicle with breathable cover.

These steps should ensure your vehicle is ready to run come spring.

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