Runs better on premium

My 08 Elantra runs noticably better on premium. ( just turned 5000 mi )On the recommended regular I don’t notice knocking or pinging but it is a little quieter on premium. Is it possible that the knock sensor or the computer is out of range?

Placebo. Have someone fill it and not tell you what is in it.

An Elantra should run the same regardless of whether you use premium or regular. You should never hear any knock or ping; it’s the knock sensor’s job to eliminate them. If the knock sensor was out of range the check engine light would come on.

You can fill your car’s tank with whatever grade you prefer, but I think you’re wasting your money putting premium in this car.

I also think this is a placebo effect. Perhaps you could confirm your hypothesis with a decibal meter?

When you use reg gas on a car that calls for premium knock sensor retards timing so you never her pinging.
This motor is not running at peak so yes there could be noise or down on power.
It will be more apperent on 4cly and 6cyl than v8s

To help learn if premium is really better, calculate your mpg too.
on my old 92 I can hear the pinging on a long grade with regular ( which the premium eliminates ), but I also get noticeably better mpg with the premium as well.

Does a 2008 Hyundai Elantra call for premium fuel?

How do you know the motor isn’t “running at peak?”

The fuel controls on a 92 and a 08 are comparable on a very low level basis. We are really getting into apples and oranges with that one.

Do you just get your gas from ONE station?? If so it could be the station.

Thanks for your thoughtfull replys/suggestions. I’m convinced of the difference–yes I get my gas from basically 1 source. Also I’ve done some research on line and there’s a ton of info out there but I don’t have the “horsepower” to boil it all down–so it’s still not clear what the answer is. Even Click and Clack’s reference to: " use premium if you have to drive your mother-in-law in hot weather or driving up mountains with a load" tells me that they don’t think it is a placebo effect–it is different! So thanks. I’ll press on and if I find out anything I’ll report back. D A form PA

What is the source of that Tom and Ray quote? Something tells me the quote is being taken out of context and that it refers to a vehicle other than your Hyundai Elantra. Were Tom and Ray talking about another 2008 Hyundai Elantra? If not, don’t apply their advice to your car.

Perhaps I should approach this from another angle. If your car runs better on premium fuel, but was designed and built for cheap fuel, there may be something wrong with your engine. If that is the case, using expensive fuel instead of fixing the problem is the expensive way out. The problem may get to the point where the expensive fuel won’t treat the symptoms anymore. You would be better off getting your vehicle repaired so it can use the fuel for which it was designed. Specifically, you should get the knock sensor and EGR valve checked if your engine has them.

If there is a problem with your engine, high octane fuel will only treat the symptoms, not the underlying problem. So if you don’t mind wasting money in the long run, and you like helping line the pockets of Big Oil, keep doing what you are doing. Money does grow in trees, after all, doesn’t it?

Does your owner’s manual say something to effect that “Premium is recommended for improved performance”? Premium is recommended for my wife’s 2006 Sienna, but it runs fine on regular.

For comparison I used Premium and Regular for about 1200 miles each in the Sienna during the same time of year. It may have run a little better on Premium (placebo effect?), but there was no measurable difference in mpg. We continue to use regular with no problems.

Ed B.

The quote is taken from their questions and answers on the debate over premium and regular on this web site. The discussion is actually about using regular instead of premium – read it. I’m drawing my own conclusion from the short, loose answers ( right or wrong}.They seem to say using premium will not increase your car’s performance --only reduce knock, but it seems to me that if you have any pre -ignition you also must decrease the efficiency of the engine. And pre-ignition will occur if the octane is too low for the engine design or ambient conditions. Now, I don’t hav any desire to make oil compannies rich and don’t plan on long term premium usage. I won’t comment on how the premium got into my tank–it is the first time this car has seen it. I had not even noted that it was there- until I noticed the better smoother sounding engine and wondered about it. Could there be a small error in the computer mix–or any other small error which improves with the higher octane? I’m not ruling out placebo ,either.

I think I found your quote. It is at

The main point Tom and Ray are trying to make is:

Does your owner’s manual say “Premium Unleaded Only”? No? Then don’t ever use premium fuel. There. We just saved you 40 cents a gallon… or $8 on a 20-gallon fill up. If your engine is designed to run on regular gas, there’s absolutely no benefit to putting in “high test.” It pollutes more, it costs more, and doesn’t give you any benefit in performance or fuel system cleanliness.

It is clear you have made up your mind though, so I am only posting this information for other readers who might benefit from the information.

“They seem to say using premium will not increase your car’s performance --only reduce knock, but it seems to me that if you have any pre -ignition you also must decrease the efficiency of the engine. And pre-ignition will occur if the octane is too low for the engine design or ambient conditions.”

Let's look at three cars.  Car A designed for regular and likely will have instructions to use regular fuel.  Car B designed for high octane but has knock sensor to retard the timing if needed, it will usually come with instructions recommending high octane fuel but will stop short of requiring it and Car C that is designed for high octane only and it should come with a warning in the owner's manual to use ONLY high octane

Today I don't believe there are many if any Car C types on the new car showroom. However using regular in it can damage the car and will likely knock.

There are lots of Car A types and many people use premium in them thinking it is better for the engine, will give them better mileage and the engine feels and sounds better/stronger, all of which is not true unless the engine has a lot of carbon build up. 

Type B cars are usually where the confusion comes in.  They will run best on high test, but if the engine detects knock (an indication of low octane) it will retard the spark to prevent engine damage and it will usually loose power and mileage.  It will not be damaged however.  It is unlikely that you would be able to hear that knock before the computer adjust the timing. 

The effect of octane varies depending on the design of the engine.

You also may have been confused with a reference to high altitudes that changes a car’s octane requirements.

I have no doubt that you’re really having the experience described. But I think a better approach would be to look into the reason it’s knocking and/or pinging.

Knocking and pinging are preignition symptoms. They could be caused by an engine running too lean or a spark too advanced. In short, something is causing excessive cylinder temps or advanced spark. The knocking sound is actually the shock wave from the explosion hitting the piston while it’s still trying to compress the gas in the cylinder. That shock travels right through the piston, the rods, and into the crank, and is extremely hard on bearings. Preignition uncorrected can even result in holes burned right through the pistons.

Even though you’d normally suspect a CEL light, you may have stored fault codes in the computer. And even it you do not, I’d still recommend a good engine diagnostic. Not properly addressing this now could cost you your entire engine.

No, I haven’t made up my mind. It seems to sound better to me and run smoother.You are telling me that it is impossible, under amy circumstance, unequivocally, to run better. Could the regular gas I was buying from a single source be sub par? You seem to be sure it is not. You have also ruled out any engine shortcoming. Seems to me, you have made up your mind. However, I agree with your math–regular is cheaper.

I guess I misunderstood. I agree it is plausible it does run better on premium. If it does, though, it is a sign there might be something wrong with the engine.