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Premium Gas in Acura - is it really necessary?

I “inherited” a 1998 Acura and on the instrument panel it states “use premium gas only”. Is it really necessary to use premium gas? What impact will there be to the engine if I use regular gas?

Premium is just a higher octane rated fuel. There is no harm in running regular 87 octane unlead in your vehicle just like there is no problem running premium in an unleaded vehicle. But gas prices these days i dont know who would be foolish enough to put premium in their unleaded vehicle. But unleaded will work fine in your car.

Hmmm…premium is unleaded. But you’re right, many cars that in the manual say ‘premium recommended’ run fine on regular. However, if the manual says ‘premium required’, I’d pay the extra $.20-.30/gallon

You only need to use premium if you plan on running the engine.

Seriously, the instructions are pretty clear: use premium only. The engine control system is designed for it and probably CANNOT compensate for lower octane fuel. The result will be preignition. Let this go on long enough and you will damage the engine. At best, horsepower and fuel economy will be reduced, and fuel cost will probably be higher than if you use premium.

It’s telling you that premium is required, so that’s what you have to use. Use of lower octane fuel will severely impact performance and fuel mileage, enough that anything you might save at the pump disappears in a hurry. The potential for engine damage from pre-ignition is another possible side effect. The engine was designed for a certain octane level, and you would do well to give it what it needs.

You can try regular gas and see how it runs. Pretty much any car made since the early 90s has ‘knock sensors’ that will retard the ignition timing to protect the engine if preignition (spark knock) is detected. If you notice performance dropping or hear spark knock, then I’m afraid you’re stuck with using higher octane gas. At this point the savings of 10?/gal. are offset by lower mileage you’ll get if the computer retards the spark, and possibly by harm you’re doing to the engine by continually experiencing spark knock if the engine management system isn’t coping perfectly. Also keep in mind that some gas stations’ version of regular or premium seem to be worse than others. My car calls for 89 octane, but I can usually get away with filling up with 87 every other tank as long as I don’t let it get too low before filling.

What part of “use premium only” is unclear to you? If that is what the car’s manufacturer specified, then that is what you need to do, unless you want to risk damage to valves and pistons. Additionally, if you do use regular gas, it is likely that your fuel economy (and your performance) will be degraded sufficiently to negate the cost savings of regular gas.

So, I would suggest that you “do the math” involved in the issue of paying a couple of dollars less at the pump vs. probable lower gas mileage and reduced engine performance + a serious risk of damaging the engine.

If the car’s manufacturer specified premium gas only, using regular gas would be a very good illustration of being “penny wise and dollar foolish”, at least IMHO.

Let me add that using regular when premium is “required” will result in less power lower mileage and, in time, a damaged engine. Since you will end up paying more anyway due to the lower mileage, why not protect your engine and get better performance and use what is required.

NOTE: when the owner’s manual says premium only or required, it means just that. When it says recommended, then it means the car will adjust for the lower octane and prevent damage to the engine, causing reduced performance and mileage as well. Most cars fit in the “recommended” class, but there are those that do “require.”

To add to what’s been said:

  1. While I’ve never designed an automotive engine, I’ve designed enough other things to respect the automotive designers when they say “use premium fuel only”. They are saying it deliberately. They are the ones who ran the engine through many hour of simulation, followed by actual testing and measurement. They are the ones who know the ranges of the anti-knock sensors and the air/fuel/timing maps. And they know exactly what happens when the octane is too low (under all operating conditions). I would be foolish to assume I know better than they do just because I read a few web sites or because my buddy did and his engine is still running, or whatever reason I had.

  2. The difference between regular and premium seems to be about 6% less (eg: 25 cents less @ $4.25/gal). If your vehicle gets 25 miles/gallon, then any drop in mileage greater than 1.5 miles/gallon means you’ll be wasting money by using regular. It’s not hard to loose 6% in mileage when dropping to regular for a vehicle requiring premium.

The difference between 87 octane and 92 octane is not enough to change the course of history or destroy your engine. Try a tank of regular and see what happens…If you can not detect any problems with your ears, there are no problems worth worrying about…

I don’t agree. The damage may not show up for some time, regardless of what sounds you do or do not hear.