Why does 91 octane feel faster than 87?

Question

My 2015 Chrysler 200S 3.6 Pentastar V6 recommends 87 unleaded fuel, however for a long while I began using 91 octane in belief that my car will run a bit better. I got into a debate with a few friends and i said 91 does improve performance, but i researched and got mixed answers mainly that i should use the factory recommended fuel which is 87 for my car. I did notice performance gain just by a bit. I was told its in my head but my proof is this: I had driven my car with probably two tanks of 91 didn t notice anything, however i lent my car to my mom and she filled up with 87, after getting my car back i noticed it drove sluggish and i felt as if the motor had more vibration. Almost thought my engine had an issue, so i pondered until i realized there was more gas, so i asked my mom and she said yea she put 87 in not 91. After that i put 91 in and i could feel the car run smoother and just right in my opinion. What do you guys think?

Answer 1

All the folks who are saying that it isn't possible - it's your imagination - learned everything they know before cars had computers. Even reputable "authorities" are still saying to use the cheapest gas that doesn't make your engine "knock and ping" !!!!!!!!!! Guess what folks: cars don't knock and ping any more unless there's something major wrong in there !



The first car I owned with a more sophisticated engine computer was also a Chrysler V6. The Owners Manual listed the maximum horsepower developed with various octane fuels. YES - it wouldn't have detonation or pre-ignition on 87 octane because the computer would adjust timing and fuel mixture to match . . . . . but it could develop more horsepower with higher octane. In actual driving, I didn't notice much difference between 87 and 92 octane while puttering around town. But a big difference in power driving in mountains - and a big difference in mpg.



The Owners Manuals of cars I've had since that Chrysler don't give the same info - but all cars use advanced engine control systems now.



The folk who refuse to believe that are out-of-date. Have you ever wondered: lots of new American hi-performance cars have compression ratios of 10 to 1, or even much higher......but run on regular gas. But buy a BMW, Porsche, Benz or other imported "exotic" and they specify high-octane - for good reason.

Answer 2

Yes your car will probably run smoother when you use the higher octane, and it will also have slightly more power and get better gas milage too. You need to decide if it is worth it for you, as the higher octane does cost a bit more. I always use 98 octane in all my high performance cars

Answer 3

Hi go ahead and waste your money if you must as no one is ever going to convince you with your mind set on this idea. hight compression engines are the only one which benefit from using a high octane fuel such as a compression ratio over 10 :1.

Answer 4

From page 531 of your owner's manual



"All engines are designed to meet all emissions

regulations and provide excellent

fuel economy and performance when using

high-quality unleaded “regular” gasoline

having an octane rating of 87. The use

of premium gasoline is not recommended, as it will not

provide any benefit over regular gasoline in these

engines."



" What do you guys think?"



Assuming your car doesn't have anything wrong with it; any perceived difference is all in your head.

Answer 5

It's all in your head. Octane is an inhibitor to stop pre-ignition in a motor caused by heat and pressure. 87 octane gasoline actually burns better than 89,91 or 93 octane gasoline because it has fewer inhibitor chemicals in it.

Answer 6

The only possible way high octane could help a car that doesn't call for it is if it had severe carbon buildup in the cylinders, causing too high compression, which was causing severe detonation.

Answer 7

changing Octane does NOT make a car Go Faster



in the UK we had 5 star petrol with 101 being the Highest i used 93 octane in my 1954 220 mercedes and i tried once using 101 the only difference was the Price

Answer 8

This is 100% undeniably in your head. The only reason some cars require premium is because they have a high compression engine (aka if they use regular their engine would knock and ping). I could put premium fuel in a Civic and nothing would happen, it wouldn't gain any horsepower and no the engine wouldnt run smoother. I might imagine it did though.

Answer 9

I can remember when we had 98 octane at the pumps back in the 50's here in the US.

Tree hugger's made it all change!



I hear that it is still available in Australia.

Answer 10

There are some modern engines that can use either fuel, but DO run better on the higher Octane. The newer Toyota Direct Injection V6s are one of them. They can run OK on 87, but they basically "detune" themselves slightly to make it safe. Difference is about 7hp, which is barely noticeable, but it can be measured on a dyno.



There is also the chance you got some poor quality 87, maybe with more alcohol compared to the 91? Alcohol contains less chemical energy than gasoline, but has a higher octane rating. So it can be added to a poor grade gas to boost the octane, at the expense of power.



So there are some possible reasons for what you have noticed, even if on paper there should be no difference,



My earlier model Toyota V6 has no difference in performance between our regular and premium gas. But that doesn't mean your engine and your gas is the same.

Answer 11

if your car is designed to run on 87, that means it is not tuned and will not properly adjust to 91, meaning whatever differences you "feel" switching to this fuel type is ********. if your car is designed to run on 91, then there would be a difference in torque



dont waste your money.

Answer 12

It is your imagination and nothing more. If you engine was designed to run on Regular then Premium will not add power, nor better mileage. It is scientifically impossible.

Answer 13

You're not Crazy. That engine has a 10.5 : 1 compression ratio and the pcm uses active knock sensors that continuously monitor the engine as the pcm runs timing up. Better gas will feel more responsive. Old tech guys don't understand how this works and probably never will.

Answer 14

I retired from a Chrysler dealership after 23 years. Our class instructors always said that 87 octane was recommended for their cars. And the additives in gas of higher octane, in some cases, build up deposits on certain types of their injectors back then in the 80's. I don't know if that applies to any Chrysler cars now.

Answer 15

It's purely psychological. Like when you clean and wax your car it feels like it's driving better.

Answer 16

Octane number is simply a rating that indicates how well the fuel resists detonation, it has nothing to do with the energy content of the fuel. 91 Octane fuel has no more energy than 87 Octane fuel does. You need more compression and more aggressive timing to extract more power from it. In fact, adding Ethanol to fuel raises Octane while lowering the fuel's energy. If your engine is not tuned for the higher Octane fuel you will see zero performance increase and may actually see a slight decrease if the Ethanol content is high. Any performance increase you think you see is all in your head.

Answer 17

Using a higher octane fuel than what the manufacture recommends is unnecessary and a waste of money.