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What Grade of Gasoline Do Auto Mechanics Recommend?

auto mechanics

Gasoline is something most of us take for granted. It is a little like buying milk. One brand is similar to the next, with price pretty much being what makes up our minds for us. Thing is, this really shouldn’t be the case. Surely, if the grades really didn’t matter, gas stations would stop selling three different kinds, right? You betcha. So, let’s take a closer look at what gasoline your favorite auto mechanics recommends.

Choosing the Right Gas for Your Car: It’s All About Timing

We first need to have a small discussion about internal combustion theory. We like to think of engines as giant air pumps. The more air they can move in a given time, without wasting energy, the better they are. All this relies on timing. An engine expects the fuel to ignite at a specific time. i.e., When it provides the spark. What it doesn’t realize is that some fuels are like teenagers. Unpredictable. So, what happens when the fuel decides to ignite before the spark? Sudden pre-ignition while still on the compression stroke causes damage to the piston, connecting rod and crank.

What Do The Grade Numbers Mean?

Engine damage isn’t cool. So, modern cars got clever. The computer senses a knock and retards the spark timing so that the ignition occurs later. Critical engine wear is avoided at the cost of efficiency. So, you’re telling us that our engines don’t run at their best all the time? Not quite.

There is another way to prevent ‘knocking’ (other than installing a doorbell). Make. Stable. Gas. Certain chemicals naturally occurring in gas have been found to make it very predictable, more specifically 2,2,4-Trimethylpentane. (No, that’s not the stuff Elvis was on.) It has 8 carbon atoms in its structure, hence the name octane.

The octane rating of a fuel (in the U.S.) is the average amount of octane it contains based off two tests. These are called the Research Octane Number (RON) and the Motor Octane Rating (MOR). We’re auto mechanics (not nerds) so we won’t discuss them here. The higher the octane number, the more stable the fuel is. So, in theory your engine should be more efficient running higher-octane fuel.

Does It Really Matter?

If cheaper gas is so bad, then why do they sell it? Hold your horses. Stochiometric combustion depends heavily on atmospheric pressure and at lower altitudes engines are more prone to knocking than higher up. It also depends very much on your vehicle. Read the manual carefully. If your auto recommends premium gas, the manufacturer most likely has a high compression engine. You could run mid or regular spec but see some loss of performance or possibly slight damage from long term use. However, if the book requires premium, then avoid it at your peril as you may damage your engine.

Help! Premium Isn’t Available

Most manufacturers have knock compensation as part of their electronic engine management. So don’t stress if you can’t get premium gas on that road trip. Just put enough in the tank to get you to another gas station and don’t drive like Jason Statham.

Auto Mechanics in Pompano Beach

If you have questions about your car, our auto mechanics can help! Stop over to our Pompano Beach Auto Repair Shop or give us a call at (954) 746-0488. There’s a lot riding on your tires, let us take care of it.

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