Car Forums  

Go Back   Car Forums > Technical Discussions > Repairs & Maintenance
FAQ Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 08-20-2007, 11:18 PM   #1
whicky1978
CF Newbie
 
Join Date: Nov 2005
Posts: 56
compression ratio vs. octane rating

If I have a 10.3:1 compression ratio, then what is the maximum octane fuel my car could handle? Does anybody know of a website with a chart?
whicky1978 is offline   Reply With Quote
Old 08-20-2007, 11:24 PM   #2
67Coronet383
CF Riff Master
 
67Coronet383's Avatar
 
Join Date: Nov 2005
Location: Under a hood, Georgia
Posts: 628
Quote:
Originally Posted by whicky1978
If I have a 10.3:1 compression ratio, then what is the maximum octane fuel my car could handle? Does anybody know of a website with a chart?
That highly depends on the motor...
__________________
67Coronet383 is offline   Reply With Quote
Old 08-20-2007, 11:29 PM   #3
whicky1978
CF Newbie
 
Join Date: Nov 2005
Posts: 56
Quote:
Originally Posted by 67Coronet383
That highly depends on the motor...

What if it's a DOHC engine?
whicky1978 is offline   Reply With Quote
Old 08-21-2007, 12:33 AM   #4
rudypoochris
CF Enthusiast
 
Join Date: Aug 2007
Posts: 114
I think you mean minimum. That depends on alot more than just static compression. What motor? It could be anywhere from 87 to 93. Is the head alluminum?
rudypoochris is offline   Reply With Quote
Old 08-21-2007, 02:15 AM   #5
whicky1978
CF Newbie
 
Join Date: Nov 2005
Posts: 56
I know the minimum is 87 AKI (R+M/2 method). Is it possible to have too much octane in gasoline for a car? I drive a 2005 Hyundai Elantra GSL.

Edit: I drive a 2001. My wife drives a 2005 PT cruiser, premium gas only gave her car 2 more miles per gallon.

Last edited by whicky1978 : 08-22-2007 at 02:40 AM.
whicky1978 is offline   Reply With Quote
Old 08-21-2007, 04:00 AM   #6
rudypoochris
CF Enthusiast
 
Join Date: Aug 2007
Posts: 114
Quote:
Originally Posted by whicky1978
Is it possible to have too much octane in gasoline for a car?

Yes sir. If you adjust timing to a certain extent you can harness the benefits of higher octane fuel, but pretty much only if you adjust for it. If you put 91 in a car meant to run 87 you won't be doing too much harm, maybe clogging some cats, foulding the chambers, and losing power, but ti wouldn't be catastrophic. Alot of engines are quite high strung though, especially modern ones. If you put 87 in a 91 modern car typically it will pull the timing which reduces power. If it doesn't have a knock sensor though, or if it is broken, then it won't notice and you will have detonation. Depending on severity of the detonation you can junk the motor, and you will be running alot less power.

Last edited by rudypoochris : 08-21-2007 at 04:02 AM.
rudypoochris is offline   Reply With Quote
Old 08-22-2007, 12:41 AM   #7
whicky1978
CF Newbie
 
Join Date: Nov 2005
Posts: 56
That sounds goood. I mostly use premium because of the extra fuel economy it gives me. I average 34-37 mpg. I'm do for a new timing belt, if they adjust the belt for higher octane, will I see better fuel economy or more power or both, or would it be the same because the car adjust according to the knock sensor?
whicky1978 is offline   Reply With Quote
Old 08-22-2007, 01:45 AM   #8
vwhobo
CF's Anal Orifice
 
vwhobo's Avatar
 
Join Date: Feb 2003
Location: Redneck Hell
Posts: 8,630
Quote:
Originally Posted by whicky1978
That sounds goood. I mostly use premium because of the extra fuel economy it gives me. I average 34-37 mpg. I'm do for a new timing belt, if they adjust the belt for higher octane, will I see better fuel economy or more power or both, or would it be the same because the car adjust according to the knock sensor?
What the f*ck is wrong with you you simple minded moron? We have already played this silly ass game with you. No matter what you think, running gasoline with a higher octane rating than your car requires WILL NOT INCREASE FUEL ECONOMY! Your Hyundai is optimized to run on 87 octane. Using higher octane gas is at best a waste of money and at worst can actually cause you to lower your fuel mileage and cause damage to your catalytic convertor.

I don't care what you think. This has been tested over and over ad infinitum by manufacturers, oil companies, private research firms, car magazines, etc. Unless you want us to believe the you are the one and only person on the face of the earth that sees decreased consumption when increasing octane in an engine that isn't designed for it, then just STFU... Moron.
__________________
Thanks for the pic, jedimario.

"Everybody believes in something and everybody, by virtue of the fact that they believe in something, use that something to support their own existence."
Frank Vincent Zappa, 1940-1993

vwhobo is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Forum Jump



All times are GMT +1. The time now is 04:02 AM.

Powered by vBulletin Version 3.5.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright 2002 - 2011 Car Forums. All rights reserved.