Gas octane facts - Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum
Ford Focus Forum
HomeContact UsAbout UsGalleryDiscussion ForumsMarketplace

Go Back   Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum > Ford Focus Tech Discussions > General Technical Chat

General Technical Chat This section is for technical discussions relating to general maintenance, electrical issues, engine trouble, and recalls.

Search This Forum | Image Search | Advanced Search    

Closed Thread
LinkBack Thread Tools Display Modes
Old 04-21-2005, 10:07 AM   #1
FF #1 Most Wanted
microtonal's Avatar
Join Date: Sep 2003
Fan#: 470
Location: Seattle, WA
What I Drive: 2012 GTI, 2014 Forester XT

Posts: 6,890
FF Reputation: 12 microtonal Great Standing Member
Buy-Sell-Trade Rating: (7)
Post Gas octane facts

Before You Buy Gasoline or Petrol

Origin of the 'Higher Octane is Better' Concept
Higher octane gasoline did reduce engine knock in older engines that used carburetors to regulate the air/gas mix. The older engines could not regulate the air/fuel mix going into the engine as efficiently as a computerized fuel injector. A carburetor in need of adjustment could cause too much fuel to be mixed with the air, which meant the gasoline would not burn completely. The excess gas soaked into carbon deposits and caused a premature ignition of the gasoline from the heat of the engine cylinder. The premature ignition made a sound that came to be known as 'engine knock.' When this happened, people would change to the higher octane/slower burning gasoline to resist the premature burn, thus minimizing the knock. Upping the octane was beneficial then, but engines and gasoline formulations changed.

Since the mid-1980s engines use fuel injectors with computers to accurately control the air/fuel mix over all temperature and environment ranges. The accuracy of the fuel injectors and computers is based on using the recommended gasoline for that engine. Most cars are designed to burn regular unleaded gas with an octane rating of 87. If the vehicle needs a higher octane rating this requirement is noted in the owner’s manual and usually under the fuel gauge and by the gas tank.

Gasoline Factors That Matter
The quality of gasoline and the additive package usually affect the rate of engine wear more than the octane rating. Basically what this means is that it matters more where you buy your gas than which grade you purchase.

Regular Unleaded Gasoline
The recommended gasoline for most cars is regular 87 octane. One common misconception is that higher octane gasoline contains more cleaning additives than lower octane gas. All octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against engine deposit build-up. In fact, using a gasoline with too high of an octane rating may cause damage to the emissions system.

Gasoline and Octane Ratings - This article defines octane ratings and provides an overview of how gasoline in made.

Mid-Grade Gasoline
The octane ratings 'regular', 'mid-grade', and 'premium' are not consistent. In the United States, for example, one state may require a minimum octane rating of 92 for premium gasoline, while another may allow an octane rating of 90 to be premium. Check the octane rating on the yellow sticker on the gas pump rather than relying on descriptive labels.

The Low-Down on High Octane Gasoline - Includes information about the inconsistency of ratings across the US.

Premium Gasoline
Certain high performance engines benefit from use of high octane fuel. For other engines, using a fuel with a higher octane rating than the vehicle requires sends unburned fuel into the emissions system and catalytic converter. This puts unecessary stress on the emissions system. For some vehicles, a rotten egg smell coming from the tailpipe signals use of too-high octane gas.

What Octane Rating of Gasoline Should I Use? - A good general reference.

Leaded Gasoline
Many countries continue to use leaded gasoline, even though lead exposure has significant health and environmental consequences and the cost of switching to unleaded gasoline is relatively low. Although greatly improved, research indicates significant health and environmental effects from use of leaded gasoline remain even in countries that have switched to unleaded fuel.

Synthetic and Reformulated Fuels
Some major cities with air pollution problems require the use of reformulated gasoline. Reformulated gasoline is an oxygenated fuel that burns cleanly but can lower fuel economy and engine performance slightly. Reformulated gasoline may cause pinging or premature burn in engines with excessive carbon deposits. Older/dirtier engines may benefit from stepping up to the next grade of gasoline.



Just reading.....
microtonal is offline  
    Quick reply to this message
Closed Thread

Bookmarks & Social Networks

Quick Reply

Register Now

In order to be able to post messages on the Ford Focus Forum, Ford Focus ST Forum, Ford Focus RS Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
What I Drive
Year, color, and model of your car. Example: 2003 Focus Centennial Edition Sedan
Your real name.
Please select your insurance company (Optional)


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools
Display Modes

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

All times are GMT -5. The time now is 06:57 PM.

Copyright 2002-2015 All Rights Reserved : Privacy Policy : Advertise Information

Focus Fanatics Ford Focus Forum offers many fun ways for you to engage with other Ford Focus Owners from across the world. Whether it be about the aftermarket performance modifications, technical how-to's, European tuned suspension or awesome fuel economy similar to the Mazda CX-3, Audi S3, Mazda MX-5 Miata and Acura TLX. You can find all Ford Focus, Focus ST and Focus RS related information here. Join our Ford Focus discussion forums and chat with local Focus enthusiasts in your area. If you own other makes have a look at Challenger Hellcat Forum, Charger Hellcat Forum, Cadillac ATS-V Forum, Cadillac CTS-V Forum, Lexus RC-F Forum, Lexus GS-F Forum, Mercedes GLA Forum, Mercedes GLE Forum and Volvo XC90 Forum.


Search Engine Optimization by vBSEO 3.6.1