I have been hearing rumors and talks about higher octane pros and cons. I talked with mechanics and they say that it can give a better performance, better gas mileage, cleaner for engine, etc and others say that it can be bad for your engine also because its stressing it out by requiring a higher temperature to burn the fuel leaving unburned fuel in your systems.

I want to hear what other people have to say about pros and cons because I have been running 91 octane in my tC ever since I got the car (with the exception of the gas tank it comes with when you purchase it).

I also have this problem with my car and I'm wondering if maybe running higher octane might cause the problem. Basically, when the car was still brand new, the engine would rev at 2900 RPMs when I'm going 80mph on the freeway, now it's revving at 3200 RPMs. Another problem I'm hearing is that when I'm going 30-35mph I hear a strange rattling noise (sounds like a rig truck on idle). It kinda sounds like the engine is knocking but only in the 30-35mph range.

Anyone know what might be causing this problem? I have 27,000 miles on it and it's on a fresh oil change. No mods and automatic transmission.

 

There's a sticky about running regular fuel in the 2az-fe. Good place to start.

Edited to add link to sticky that's linked above this post.

https://www.scionlife.com/forums/viewtopic.php?t=253510

 

Unfortunately that's normal. I'd say mine sounds like a bag of marbles.

Stop throwing money away, switch to 87 octane, it won't be any slower.

 

NO higher octane is not bad for an engine, but DONT USE IT because you are only hurting your pocket the car runs better on 87 octane trust me and others will tell you,.



the highway rpms u might just not remember that it was always at 3200, our gearing really sucks so yea 3200 sounds about right,



the rig truck sound your hearing is normal the 2az-fe is known to have loud valvetrain chatter and the injectors are loud....this is normal only thing u can do to quite this down is to shim the head but why pay so much money to fix a normal thing

 

higher octane is better however if your boosted. . if your not, i wouldnt waste the money.

 

i ran 89 for a while then went back to 87... my car ran better and i saved more money. just like steve said, if ur NA dont bother.

 

the gas out of the pump has the exact same cleaners in every grade,so unless you are boosted you do not need to run higher than 87........car was designed to run on it.......no need to give the rich oil companies your money........heck you can give me your extra .40c a gallon if you want .......87 is all you need till you boost.

 

While it's often the same cleaning agents, the premium fuels usually have higher concentrations of them. As an example, Chevron adds their Techron cleaner to all grades of gas they sell, but the premium has more Techron in it. Regardless, the tC only needs 87 octane.

 

Posting And You...

it's a STICKY..
(you dumba$$)