Posts Tagged ‘automotive care’

Car Quiz – Octane Rating

Tuesday, March 10th, 2015

What does the octane rating (e.g. 87, 89, 93) for gasoline quantify?

a) the ratio of higher quality fuel to oxygenates present
b) the ability to resist engine knocking or pre-ignition
c) the amount of engine-cleaning detergents added
d) the capacity to improve combustion efficiency and increase performance

The correct answer is (b) the ability to resist engine knocking. Engine knock, also called pinging or pre-ignition, occurs when the fuel-air mixture ignites prematurely by compression rather than normally by spark. This abnormal combustion, which may be caused by several factors, decreases horsepower and can damage the engine over time. The octane rating represents how much the fuel can be compressed before it spontaneously ignites. It does not mean that the gas is a higher quality, or will improve performance, or clean the engine better. Although high-performance cars tend to have higher engine compression ratios and therefore may need a high-octane gas, the majority of cars require no more than 87 octane. Save yourself some money at the gas tank by using the lowest octane rating recommended for your vehicle. You can find this information in your owner’s manual. If your engine and other components are operating properly, and you are using the recommended octane level for your car, you should not experience any knocking or pinging. If your engine is knocking, you can try a higher-octane gas to alleviate the symptoms, but it is best to have the true underlying problem diagnosed and repaired.

Car Quiz – Tire Pressure

Friday, August 26th, 2011

Q: What is the correct amount of air pressure for your tires?
a. it is listed on the inside frame of the driver’s door
b. it is imprinted on the sidewall of the tire
c. 32 pounds per square inch (psi)
d. 30 psi in winter, 34 psi in summer

A: Many people believe the number shown on the outside of the tire to be the correct answer, but that is actually the maximum pressure allowed. In other words, you really don’t want your tires quite that full of air! 32 psi may be the answer for many tires, but certainly not all of them, so don’t just assume it to be applicable to your car. And although (d) raises an important point about the difference in air pressure when hot vs. cold, this one-size-fits-all kind of answer for tire pressure still doesn’t work. (Incidentally, the most accurate way to measure tire pressure is in the morning when the tires are cold, before having been driven.) The correct answer is (a) – you should be able to find the recommended tire pressure for both front and rear tires listed on the driver’s door jamb. (If it’s not there, check your glove compartment door or owner’s manual.) This pressure has been determined to provide the optimal combination of performance, handling, and gas mileage for your vehicle.


  • A/C Systems
  • Alignments
  • Batteries
  • Belts and Hoses
  • Brakes
  • Computer Diagnosis
  • Cooling Systems
  • CV Axles
  • Electrical Repairs
  • Emission Repairs
  • Engine Performance
  • Engine Repair
  • Exhaust Systems
  • Fuel Systems
  • Oil changes
  • Pre-Purchase Inspections
  • Road-Trip Inspections
  • Scheduled Maintenance
  • Steering/Suspension
  • Timing Belts
  • Tires
  • Transmissions
  • Tune-Ups
  • Warning Light Diagnosis

Catherine's Mission Statement

To provide high quality auto repair with integrity, honesty, and excellent customer service, all at a fair price and with a personal touch!