Cars that say premium gas only, what happens if you don't use premium gas?


I am looking for my wife a newer car and have considered some that clearly say only use Premium gas. Will the low grade gas damage anything in the car? I have just always considered the higher grade gas a waste of money. Is there any proof that the car runs better on the premium or will get damaged on the lower grade gas? I always wondered if the gas companies and the car companies were in bed together to promote their products. I’ve been looking at several different models by Lexus. They all seem to require premium gas. Thanks in advance.


because you mention Lexus

Can I use a lower octane fuel in my vehicle than what is recommended to save money?

We do not recommend using a lower octane fuel than what is recommended for your particular vehicle. Use of gasoline with an octane rating lower than what is recommended may result in engine knocking. Persistent knocking can lead to engine damage.

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The premium gas has a higher octane level than regular gas. This higher octane level prevents pre-ignition or pinging/knocking of the engine under power.

Some engines have knock sensors that detect pinging/knocking so the computer adjusts the engine to prevent that from occurring. Which causes the engine to lose performance.

The reason why knocking/pinging should be avoided is, it can damage the engine.



A car that requires high octane fuel is the one time it is not a waste of money.

If you’re not going to pay for high octane fuel, you shouldn’t buy a car that requires it.

Buy a car that uses cheap fuel if you’re too cheap to buy anything else based on the car’s needs.

Now, if an owner’s manual only recommends high octane fuel, there is room for debate, but if it’s required, the choice is much simpler.


Why do people who don’t want to use the fuel required ( Premium ) even look at those vehicles .
And no there is not evil plot between the manufactures and oil companies .


So you’ll spend a lot of money on a Lexus, but balk at spending a lousy hundred fifty bucks a year on the fuel that the manufacturer says is required? I figured that at 15000 miles per year, 25 mpg = 600 gallons at an extra 25 cents per gallon. I’ll not get into the technical details of octane levels, compression ratios, detonation, etc, because if you believe premium gas is a conspiracy you won’t listen anyway.


Unfortunately, in recent years, it seems that everyone who disagrees with established scientific principles dismisses reality by calling it “a conspiracy”. I guess that type of “head in the sand” behavior is easier (in the short term) than reading widely, and educating one’s self.

Alternatively, those of small minds will label anything that conflicts with their preconceived–and baseless—notions as “fake news”. I guess that is also easier (in the short term) than dealing with reality.


This is probably rude but I looked at your profile and you have a lot of threads where you had problems with older vehicles. Things like used Lexus and other luxury vehicles are not cheap . None of my business but I would look at something new in your price range . Advantages are : 1. Warranty 2. Lower finance rates 3. Some even give free service for oil changes and road side service ( our 2018 Ford has 5 year roadside service ) 4. You don’t have to worry if the required maintenance was done.


When the vehicle calls for premium gas only, it means in order for the engine to operate normally and not detonate, premium gas should be used. Premium gas has a higher octane rating, which is less prone to detonate.

The engine likely calls for premium fuel because it running with a higher compression ratio for more power. Higher compression engines are prone to detonating, hence the premium fuel.

However, as of the last 23+ years, engines have a “knock sensor” to detect if detonation is happening in your engine, which would likely happen if you used regular fuel. When that sensor detects denotation, it will retard your engine spark timing to prevent the damaging denotation from happening.

While the above spark retarding may sound good, it results in lower engine power, often poorer drive-ability, and usually a drop in gas mileage. There’s also a risk that if the knock sensor ever becomes defective and doesn’t retard the timing when it should, engine damage may occur.

Some people do run regular gas in cars that require premium, and they aren’t bothered with the negative effects mentioned above. It’s not something I would do.


Good info above. I’ll add that when an engine “knocks” from using too low octane, it means the gasoline is exploding before it should, before the spark plug fires, earlier on the piston’s upstroke. This causes the piston to be forced down by the gasoline exploding at the same time it is moving upward, and this immovable object vs unstoppable force situation eventually will damage something inside the engine. I expect your engine has a knock sensor to prevent that from happening, but the knock sensor can fail. Also if the way the computer handles a low octane fuel situation is by retarding the ignition, that can cause the engine to overheat. Some engine designs are more sensitive to all of this than others, and that’s why some will say high octane recommended, and others will say high octane required. Best to follow the manufacturer’s recommendations, as they have engineers studying that sort of thing.


2011 and newer Lexus ES350 and the CT200h use regular unleaded gasoline, most other models use premium gasoline.

When a vehicle is certified with the EPA for emissions and fuel economy using premium gasoline the owners manual must state that premium gasoline is required. Not everyone uses the correct fuel in their vehicles, do they notice that there is less than 300 horsepower when using regular gasoline?


I can’t help but wonder if these problems might be brought on or exaserbated by using the wrong fuel, or using cheaper oil than the manufacturer recommends.


The delta between regular and premium has been growing steadily for the past decade. It’s way above 25 cents a gallon these days. The places I use tend to sell Premium for 40 cents a gallon more than regular (my daily driver takes premium, so I that’s why I go to those particular stations), but there are plenty of places that charge 60-80 cents a gallon more for premium.


Trying to win friends are you ? OK fine.


Not trying to win friends, trying to keep people from gettin ripped off. Think about it pragmatically, preignition is a hoax to get you to pay more. It’s ok though buddy!!!




I have had a number of cars that required premium gasoline and there was a marked difference in the way the car ran if regular was used. Granted, these were carbureted, points-ignition cars and the technology did not exist to keep them from knocking and pinging and dieseling like a modern day car, but the fact remains that the engine will not run as well as designed if a lower octane is used.

Do the math and figure out exactly how many dollars a week you can save by using regular. I’d be surprised if it’s as much as one stop at Starbucks.


That rattling knocking sound I heard before the valves deformed to the shape of a tulip is a hoax? Fixing it was no joke.


If you say so.

But what does that have to do with the price of tea in China?

If a car can be run on E85, that’s just a capability it has, the owner is free to use straight gasoline or lower ethanol blends (E10,E20) if they want to. Some enthusiasts will tune their engines to run on E85 as it’s a very high octane fuel. However it has fewer BTU’s than gasoline so you have to burn more of it. It’s usually cheaper just to use gasoline .

On older vehicles perhaps, but any car made in the last two decades or so will run on E10 without issue.

So you just go around spreading your sage advice to people who likely know just as much, if not more about the subject than you do? Whatever helps you get through day I suppose.


If you think pre-ignition is a hoax, then I think you are a putz.