Question: It seems like there are a lot of conflicting opinions on when to change the oil in a Corvette. I've been changing the oil in my '09 convertible every 3,000 miles; is this too often? Should I just follow the car computer? Do I need to change the filter on every oil change?
David
Via the Internet

Answer: This seems like it should be a simple question to answer, but sometimes things aren't as simple as they seem. Let's start by covering the basics. You need to change your oil on a regular basis, because all motor oils break down over time. Once that breakdown has occurred, the oil loses its ability to protect your engine.

Besides lubricating an engine's moving parts, motor oils are designed to carry combustion byproducts away from the pistons and cylinders. Oil is also formulated to collect dirt and dust that enter the engine through the intake and condensation that forms due to heat cycling. Engine oil must also contend with any coolant or fuel that gets in the crankcase, as well as any acids that may form from the reaction between water and other contaminants.

This all means that the more you drive your car, the more the oil will become contaminated. Oil additives are used up over time, and the oil itself can oxidize or thicken, preventing it from doing its job. While knowing this may make you want to change your oil every time you start your engine, today's oils are remarkably resilient and long-lasting. That said, how often you change your oil should depend on several factors.

To determine the rate at which contamination and additive depletion occurs, we need to consider climate, driving conditions, fuel-injection or carburetion adjustments, and the general mechanical condition of the engine. In a perfect, climate-controlled world, with ideal driving conditions and an optimally tuned car, you could easily go 7,000 to 10,000 miles between oil changes. But since none of our vehicles operate under such conditions, I think you're doing the right thing by changing your oil every 3,000 to 3,500 miles.

In some circumstances you'll need to change your oil more frequently than you normally would. These include a misfiring engine or extremely cold operating conditions, which can cause raw fuel to be introduced into the crankcase. Driving the vehicle hard-as you would at a road-course event or during a night at the dragstrip-will also require more-frequent oil changes. It's also a good idea to change the oil if you're getting ready to store your Corvette for the winter. This will remove any contamination and acids from the crankcase, so no bearing damage can occur during storage.

Every time you change your oil, you should change the oil filter as well. Most areas have oil-recycling centers that will take your used oil and filters. You can also check with your local parts store to see if they have a similar disposal program. Finally, always check your owner's manual for the type of oil you should use and the frequency with which you change it.

Question: I have an '04 Z06 with an in-tank fuel-pump/fuel-filter assembly. How often does the filter need changing?
Mike in Tennessee

Answer: We've had several questions on this topic, Mike. Fuel filters located inside a fuel-pump module are generally considered lifetime units and should only be replaced if the pump fails. In fact, you could create a lot of problems by trying to replace the filter as part of your regular maintenance regime. Since there have been very few instances of in-tank filters becoming clogged, the old maxim of "If ain't broke, don't fix it" definitely applies in this case.

Question: This isn't really a tech question, but here goes. I was at a local Corvette show, and a few of the guys I know were talking about the first Corvette. One of them stated that it used an American flag for its emblem. Is this true, and how did the Corvette emblem originate?
Lance from Florida

Answer: Wonderful question, Lance. History has always been a favorite subject of mine, and the history of the Corvette emblem is quite entertaining. In the case of the original "Waldorf" Corvette, a man named Robert Bartholomew designed the emblems that adorned the hood and the center of the steering wheel. But his first design-which featured a checkered flag on the right side crossed with an American flag on the left-was never seen by the public. At the last minute, someone on the legal staff at GM halted the unveiling, stating, "You can't use the American flag on a commercial product."

This decision created an urgent need to create a new emblem design in a matter of hours, since the car it was going on was already in New York. Bartholomew tried to contact the Chevrolet family, to obtain a copy of the family crest, but he was unsuccessful. Then he had an epiphany. "Chevrolet is a French name," he thought, "and the fleur-de-lis seems very French to me." He then created a flag that combined a blue Chevrolet Bow Tie and a fleur-de-lis crossing staffs with a checkered flag. With the aid of a plastics shop in Detroit, he created the emblems and had them sent to New York, where they were installed just in time for the unveiling of Chevy's new sports car. One of the original emblems was saved and is currently on display at the National Corvette Museum in Bowling Green, Kentucky.

Question: I own a '64 Corvette that has a modern drivetrain but retains the factory body appearance. After the car was last painted, in 1990, the seams where the panels were bonded together became visible. About five years later, small cracks appeared where the seams are. Now I'm planning to have the car painted again. The body shop I'm using said they would apply some body filler to these locations, but that with time, the car would crack again. Is this true, or can I repair this problem before the paint is sprayed?
Mark
Via the Internet

Answer: First off, find a different body shop! You need one whose techs are accustomed to dealing with Corvettes and their unique problems.

Let's run through the steps for permanently filling the bonding seams. Note that this is a messy job that can cause skin irritation. Remember to wear safety goggles and gloves any time you work with fiberglass or resins.

The surface should be clean of all waxes and grease. You can use a pre-cleaner for this purpose.

The areas to be repaired should be dish-ground (concave) with a 24- or 36-grit sanding disc until deep enough to allow for the application of three layers of fiberglass mat. Fiberglass cloth should not be used, since the woven texture has a tendency to show in the finished product.

After grinding, blow away any residue with clean, dry (oil-free) compressed air. Solvents should not be used, since they can soak into the raw fiberglass and affect bonding or cause a solvent "pop" in the paint at a later time.

Cut your fiberglass mat into three different widths. You'll be applying these to the dished area, starting with the widest one on the bottom. After cutting the mat, pull some of the material off of the cut edges to fray them. This will allow for better bonding and prevent sharp edges.

When mixing the fiberglass resin, only mix the amount you'll use in a 10-minute span. After that, the resin will begin to harden. Note that the working time will vary with ambient temperature and amount of hardener you mix in. Follow the guidelines below, and remember to work only one panel at a time.

Brush the prepared area with resin.

Lay the fiberglass mat in the prepared area and thoroughly brush the resin into the mat.

Use a fiberglass roller to apply the resin-mat mixture to your Corvette. The roller will help force any air bubbles and excess resin out of the material, allowing for greater strength.

Once you've finished applying the first layer of fiberglass, immediately apply the second layer.

After you've finished applying the second layer of fiberglass, immediately apply the third layer.

Got a question for our Tech Corner expert? Just jot it down on a paper towel or a lightly soiled shop rag and send it to us at VETTE Magazine, Attn: Tech Corner, 9036 Brittany Way, Tampa, FL 33619. Alternatively, you can submit your question via the Web, by emailing it to us at vette@sorc.com. Be sure to put "Tech Corner" in the subject line.

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