Scion tC Forums banner
1 - 16 of 16 Posts

· Registered
Joined
·
583 Posts
Discussion Starter · #1 ·
The recommended octane is 87 for the tC, from what I've read (dont have the tC yet). Yesterday I noticed that the octane levels here (texas) go from 86 (regular) to 89 (plus) but no 87.

Is it better to stick with 89 or will 86 cause a lot more wear on the engine? Does one level make a big difference?
 

· Former '05er
Joined
·
12,590 Posts
Originally posted by pinky25@May 9 2005, 12:14 PM
The recommended octane is 87 for the tC, from what I've read (dont have the tC yet). Yesterday I noticed that the octane levels here (texas) go from 86 (regular) to 89 (plus) but no 87.

Is it better to stick with 89 or will 86 cause a lot more wear on the engine? Does one level make a big difference?
What's your elevation?
 

· Registered
Joined
·
583 Posts
Discussion Starter · #4 ·
QUOTE
you could fill up half with 86 and half with 89 and get 87.5  . just get 89 if you cant find 87.[/b]
Its actually 88, my bad! But still no 87 to be found. I just went to fill up yesterday and checked again. No 87. I guess Ill have to go with 88.


QUOTE
What's your elevation?[/b]
I dont know, I'm in the el paso area if it helps. What does elevation have to do with gas octane levels?
 

· Registered
Joined
·
1,412 Posts
87,89,93 here Im usualy hitting up the 89
 

· Former '05er
Joined
·
12,590 Posts
Originally posted by pinky25@May 13 2005, 08:19 AM
I dont know, I'm in the el paso area if it helps.  What does elevation have to do with gas octane levels?
Your elevation has a lot to do with octane. The higher the elevation, the lower the octane requirements because the absolute amount of air getting in the engine is less. Less molecules, less temperature rise on compression, lower compressed temperature of the a/f mixture, lower probability of autoignition=fewer problems with detonation, therefore, you can run lower octane than you would need at sea level. El Paso is nearly 4000 feet in elevation (the airport is at 3958 ft), so you can run lower octane fuels without worries. 86 will be fine for your tC.

You will be down on power compared to sea level though. There's no escaping that, ever, even with FI. You are always starting from an input pressure and adding boost at a ratio of pressures, not to an absolute pressure (unless your compressor is so big it is always running in excess of the engine's needs, but that's a different discussion).

So, high altitudes get lower octane fuels than lower altitudes because they don't need higher octane. You are in a place where 86, 88, and 91 are the equivalents of 87, 89, and 92 at sea level. The gasoline companies know this, and formulate fuels to work well at your location. It's also cheaper for them to produce lower octane fuels, but again, that's a different post.

If you are interested in gasoline and would like to read a bit, check out the gasoline FAQ at this site. It's getting a little old now, but the basics are all there, and you have to start with the basics anyway. After you've read this whole thing, I also have a few links for detonation that are helpful to understand what it is, why it happens, and what it means to you as the engine owner/operator.
 

· Registered
Joined
·
112 Posts
again lances provides everyone with sound info!!!
 

· Registered
Joined
·
6,498 Posts
We'll have to wait on Lance to tell us why, but I've been told by someone who would know that using premium gasoline in an engine not designed for it will actually give you worse performance...
 

· Registered
Joined
·
662 Posts
When i bought my car I was filling her with 93 then the gas went up high in the sky so i started to fill her up with 89 and few days ago i filled her up with 87 and the car started running like ####. I'm serious i know it won't make any difference, but it did it was very noticeable. It would choke in low rps ( no chokes wiht 89 when leaving her running by herself ). Even acc felt different. I don't know it might have been cuz of the 90 degree days we had in Chi-town and the next day we had 60 degree. Or maybe, cuz i had my oil changed. But it really felt different maybe Lance can help here.
 

· Former '05er
Joined
·
12,590 Posts
Or maybe because you should have reset the ECM after changing the fuel. The ECM learns by monitoring the engine and makes adjustments. First rule, after any significant change, reset the ECM. Otherwise it's just using the old calibration to figure out what to run. Not usually a good thing.
 
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top