Do you have a question about automotive maintenance, repair or ownership? E-mail us! We’ll take the time to explain the technical aspect of your situation, as well as how it affects you.

Q: My “Service Engine Soon” light is on. Someone told me it’s probably just a glitch. Is this true?

Most likely your light isn’t on because of a “glitch.” The vehicle monitoring system is extremely reliable and stable. Before your vehicle’s Engine Control Module (ECM a.k.a. primary computer) triggers the light, it monitors the suspect circuit for a set number of vehicle starts and stops to protect against false alarms.In some cases, the light may seem to turn on and off at random. This is because the suspect component is performing up to standards at times and then falling below on other occasions. Just as your ECM watches a component before triggering the light, it turns off the light if the suspect part performs as intended for a length of time. Once a faulty part degrades completely, your light will stay on until the part is replaced.

Q: I’ve heard that a loose gas cap can trigger the “Service Engine Soon” light. Is this true?

Yes, it is. If you have a loose or missing gas cap, fumes from your gas tank are escaping into the atmosphere and your computer detects a leak and increased emissions. On some vehicles, you can properly install the gas cap and the light will turn off. (This may take some time, depending on your driving habits. A service technician can confirm the light is on due to a gas cap issue and reset the system at minimal cost.) Other vehicles require the assistance of a service technician to reset the light.

Q: Is synthetic oil better for my vehicle than conventional motor oil?

If you change your oil regularly and your vehicle is designed for conventional oil, you gain no value in using synthetic oil. However, if you extend your oil change intervals to 5,000 miles or more, or if you use your vehicle for towing or plowing, using a synthetic oil will help protect the engine from excessive wear. This is because synthetic motor oil doesn’t break down as fast as conventional oil and is more tolerant of heat.

Some newer luxury and performance vehicles require the use of synthetic oil. If you own one of these vehicles, be sure to always use synthetic oil. Failing to do so is likely to jeopardize your new car warranty and will most likely lead to premature engine wear.

Q: If I go anywhere but the dealer while my vehicle is still under warranty, will it void my warranty?

Absolutely not. By law, you may have your vehicle serviced at any repair facility of your choice. As long as the services are performed properly, the manufacturer cannot void your warranty. This is why it’s important to maintain a history file.

The only time you are required to return to the dealer is for warranty repairs and recalls. Even then, you may have those repairs done at any repair facility, but the vehicle manufacturer will not cover the cost.

If you have your vehicle serviced at an independent repair facility while under warranty, the service advisors and technicians will make you aware of any needed warranty work so that you may return to the dealer and have the repair covered at no charge to you. At C&M, we take this a step further: We’ll identify the warranty work and take the car to the dealer for you!

Q: If a dashboard warning light comes on, should I pull over and call a tow truck?

It depends on the color of the light. A red light means you need to seek service immediately. There are two courses of action to take here. If it’s a warning light related to your engine, such as an oil pressure or engine temperature warning, pull over as soon as it’s safe, turn off your engine and call your auto service provider. This can be the difference between an inconvenient tow and catastrophic engine failure.

On the other hand, if you see a red battery or alternator light, your best bet is to drive directly to a repair facility. Your vehicle is detecting a problem with the charging system and may not start again if the engine is turned off.

An amber light, such as the “Service Engine Soon” message, means you need to seek service, but this can be done at your earliest convenience. Unless the engine is hesitating or bucking severely, you can bide your time—a bit.

Two other notes on your dashboard warning lights:

  • Do you know what each of the lights on your dash means? If not, your owner’s manual can provide a basic explanation.
  • All of your warning lights are designed to illuminate momentarily when you turn the key in the ignition. This is a test cycle for the bulbs. Occasionally watch to be sure all of yours are working properly.

Q: Would you recommend purchasing an extended warranty?

Yes, if you are planning to keep your vehicle well beyond the factory warranty period. While you don’t have to buy the warranty the day you drive your car home, you do want to purchase the policy before your new car warranty expires, typically around 3 years or 36,000 miles. Vehicles meeting this criteria qualify for a “new car policy,” which offers more extensive coverage at a better price than “used car coverage.” Click here to read more on our Extended Warranty page.

Q: Is it better for my engine to splurge on premium fuel?

Only if your vehicle is specifically designed for it. In most such vehicles, there will be a “Use Only Premium Fuel” note on or near your gas gauge. If you’re not sure, refer to your owner’s manual for the recommended grade of fuel.

If your vehicle is like most, it won’t benefit from 89- or 91- or even 93-octane fuel, and you’re simply throwing your money away. In fact, using premium fuel in a vehicle designed for 87 octane can actually cause starting problems in extreme cold temperatures. High-octane fuel burns slower and cooler, essentially making it harder to light the fire.

Conversely, running 87-octane fuel in an engine designed for premium grade can cause severe engine damage because the fuel will ignite before the engine is ready. At the very least, engine performance is likely to suffer.

Q: My tire sidewall calls for 35 psi of air, but my owner’s manual recommends 32 psi. Which is correct?

Always defer to your owner’s manual for the correct tire pressure. A quicker reference may be a sticker or silver placard, which you’ll find in your door jamb, glove compartment or fuel door. The psi on the tire sidewall is actually the maximum inflation for the tire. It doesn’t take your vehicle into account.

Here are two more tire tidbits for you:

  • Overinflated tires affect ride quality and often lead to premature suspension and tire wear.
  • Remember to check your spare tire pressure periodically—especially before a long trip. You never know when you’re going to need it, and even though it’s not being used, it will lose air through the years.

Q: Do anti-lock brakes help me stop faster?

No, but they will help you stop straighter. ABS is designed to prevent a loss of steering control during severe braking and manuevering conditions. Without ABS, you lose the ability to steer when the tires lock up. ABS pulses the brakes so the tires continue to grip the pavement. Because ABS releases braking pressure, it can actually take longer to stop the vehicle.

If your ABS dashboard warning light is on, it means the system’s computer has sensed a problem and has disabled your ABS. Although your ABS will not function while the light is on, you will still have regular braking. (The same is true of your airbag system. If your “SRS” warning light is on, it’s because the computer has sensed a problem with your airbag system. If the vehicle is involved in a collision, the airbags might not deploy.

Do you have a question about automotive maintenance, repair or ownership? E-mail us! We’ll take the time to explain the technical aspect of your situation as well as how it affects you.

Hours Of Operation

Monday7:00AM - 6:00PM
Tuesday7:00AM - 6:00PM
Wednesday7:00AM - 6:00PM
Thursday7:00AM - 6:00PM
Friday7:00AM - 6:00PM
Saturday CLOSED
Sunday CLOSED
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C & M Auto Service Inc. – (847) 724-6311
1830 Pickwick Ave , Glenview, IL 60026