Is it OK to use regular grade gas or do I need to use super in my car?
The primary reason to use a gasoline that is formulated to provide the minimum octane specified by the manufacturer is to prevent pre-ignition. Pre-ignition results in the knock sound that people hear when a car’s engine is under load either accelerating or going up a hill while using gasoline with an octane rating too low for the engine in current operating conditions.
Pre-ignition is caused by gasoline that ignites prematurely in the cylinder. This causes the knock sound. The sound is actually the pistons banging against the cylinder walls and/or bearings out of sync with the engine’s compression and explosion phases. These forces apply extra stress upon engine bearings and other engine moving parts. Severe knocking can lead to premature engine problems involving expensive repairs of pistons and bearings.
Most car engines produced in the last 10 years have knock sensors. These devices actually listen for the knock sound and adjust — via a computer — the engine’s timing. The knock sensor reports to the computer and the computer de-tunes the engine to reduce knock as well as making it run at a less than optimal efficiency and output.
Therefore, even though the driver does not hear a knock — because it was prevented by the engine de-tuning itself and preventing a knock — the engine is running less efficiently than it could.
Pre-ignition indicates that the engine is not getting the maximum energy out of the gasoline’s ignition. Proper ignition is nearly knock-free and will yield the most horsepower that the engine is capable of producing.
If the reason to use a lower gasoline grade is to save money, you may cause the engine to run less efficiently and therefore the vehicle may operate at a somewhat lower mile per gallon rate. It would require controlled testing, but it can safely be assumed that lower octane gasoline will cause an engine to produce less power and therefore the vehicle will get fewer miles per gallon.
There is a trade off relationship between mpg and octane. Trying to save a few pennies at the pump can result in the need to buy more gasoline more often at the pump.
Wise economy and optimal engine performance will be achieved by using the octane level recommended by the manufacturer for the specific engine in your vehicle.