If your car runs well on lower octane, don't worry about it

  • Article by: PAUL BRAND
  • Updated: March 23, 2012 - 3:37 PM
Q The owner's manual for my new vehicle recommends gasoline with 87 octane or greater. On a recent trip in Montana, I noticed their regular is 85.5 octane and their next level up is 88 octane with 10 percent ethanol. I used a half-tank of 85.5 and noticed no difference, but after reading the owners manual about 87 or better I used the 88 octane for as long as I was in Montana. Why does Montana rate theirs at 85.5, and would it have made a difference in the long run if I used that rating?

A As I said in my response to a previous question [March 3] about octane, a key measure of octane is the fuel's resistance to pre-ignition or detonation. In other words, higher-octane fuels require more heat and pressure to ignite. At higher elevations, air is less dense, meaning fewer air molecules per cubic foot of air that is drawn into an engine. Less dense air effectively lowers the compression ratio of the engine, meaning the cylinder will develop less heat and pressure during the compression cycle. That means a lower-octane fuel can be used without pre-ignition and/or detonation.

The Montana Weights and Measures Bureau has this to say: "While the minimum antiknock rating in Montana is 85.5 for regular unleaded fuel, that is not necessarily what is found. Due primarily to competition and/or multiple suppliers of refined products, regular unleaded gasoline found in western and northeastern Montana usually has an octane rating of around 87.0. Central and southern Montana's fuel octane rating is generally found to be between 85.5 and 86.0."

Since your vehicle apparently operated well on the lower-octane fuel at those altitudes -- no worries. Today's computer-controlled engine management systems can and will adjust fuel-air mixture and ignition timing to safely operate on a variety of octane ratings.

And remember this axiom: Operate your vehicle on the lowest-octane fuel that provides good performance, driveability and fuel economy. Any additional octane is unnecessary and a waste of money.

Q I have a 2009 Ford Focus with 50,000 miles on it. Yesterday, the interior dome light came on while I was driving, and now it does not turn off. It does not turn off with the headlights or with the manual on/off switch, and it does not dim after a few seconds upon leaving the car. It finally turns off after about 10 minutes of leaving the car parked. What could be wrong?

A The body control module (BCM) has extensive self-diagnostic capability that a scan tool can read as fault codes. Check for codes from the door-ajar switches or the smart junction box. Right now, the interior lights are finally being turned off by the battery-saver function.

Q I have a 1998 Honda Civic with 47,600 miles. When I straighten the steering wheel after making a left-hand turn I occasionally hear a "ping." Is this a cable in the steering column? What is the problem, and how much would it cost to have repaired? I'm now unemployed, so I've put off having this checked out.

A The most likely cause of a "ping" or "clunk" in the steering/suspension is a worn component such as a strut bushing, control arm bushing, ball joint, steering rod end or upper strut bearing. A loose steering rack or a worn U-joint in the steering column might cause noise when straightening the steering wheel. There are no structural cables in the steering system.

There's no way to know what's causing the noise or the potential cost of repair without having the steering and suspension checked by a professional. I'd suggest making an appointment at a reputable tire shop or a dealer for an inspection and estimate. This could be a safety problem, so don't put this off.

  • get related content delivered to your inbox

  • manage my email subscriptions

ADVERTISEMENT

Kansas City - J. Vargas 7:07 PM
San Francisco - R. Vogelsong
Detroit 10/26/14 8:30 AM
Atlanta
Buffalo 10/26/14 12:00 PM
NY Jets
St. Louis 10/26/14 12:00 PM
Kansas City
Houston 10/26/14 12:00 PM
Tennessee
Minnesota 10/26/14 12:00 PM
Tampa Bay
Seattle 10/26/14 12:00 PM
Carolina
Baltimore 10/26/14 12:00 PM
Cincinnati
Miami 10/26/14 12:00 PM
Jacksonville
Chicago 10/26/14 12:00 PM
New England
Philadelphia 10/26/14 3:05 PM
Arizona
Oakland 10/26/14 3:25 PM
Cleveland
Indianapolis 10/26/14 3:25 PM
Pittsburgh
Green Bay 10/26/14 7:30 PM
New Orleans
Washington 10/27/14 7:30 PM
Dallas
New Orleans 10/30/14 7:25 PM
Carolina
Buffalo 2 FINAL
San Jose 1
Boston 6:00 PM
Toronto
NY Rangers 6:00 PM
Montreal
New Jersey 6:00 PM
Ottawa
Dallas 6:00 PM
NY Islanders
Detroit 6:00 PM
Philadelphia
Chicago 7:00 PM
St. Louis
Pittsburgh 7:00 PM
Nashville
Tampa Bay 7:00 PM
Minnesota
Florida 8:00 PM
Arizona
Washington 9:00 PM
Calgary
So Florida 17 FINAL
Cincinnati 34
Troy 13 FINAL
South Alabama 27
BYU 30 FINAL
Boise State 55
(6) Oregon 59 FINAL
California 41
North Texas 21 FINAL
Rice 41
UAB 17 FINAL
Arkansas 45
Rutgers 24 FINAL
(16) Nebraska 42
Maryland 7 FINAL
Wisconsin 52
Texas 0 FINAL
(11) Kansas State 23
Minnesota 24 FINAL
Illinois 28
Memphis 48 FINAL
SMU 10
North Carolina 28 FINAL
Virginia 27
San Jose St 31 FINAL
Navy 41
Northern Ill 28 FINAL
Eastern Mich 17
(25) UCLA 40 FINAL
Colorado 37
Akron 21 FINAL
Ball State 35
Massachusetts 35 FINAL
Toledo 42
Ohio U 21 FINAL
Western Mich 42
Ga Southern 69 FINAL
Georgia State 31
Kent State 3 FINAL
Miami-Ohio 10
Oregon State 14 FINAL
Stanford 38
Boston College 23 FINAL
Wake Forest 17
Central Mich 20 FINAL
Buffalo 14
Fla Atlantic 16 4th Qtr 1:20
(23) Marshall 28
Louisiana Tech 31 4th Qtr 2:53
Southern Miss 20
(1) Miss State 38 4th Qtr 9:26
Kentucky 24
Georgia Tech 56 4th Qtr 3:37
Pittsburgh 28
(22) West Virginia 27 4th Qtr 3:21
Oklahoma State 10
Texas Tech 27 3rd Qtr 0:39
(10) TCU 68
Michigan 3 4th Qtr 4:43
(8) Michigan State 28
Vanderbilt 7 4th Qtr 9:39
Missouri 17
Old Dominion 51 4th Qtr 13:30
Western Ky 56
UNLV 13 4th Qtr
Utah State 27
Temple 14 2nd Qtr 0:12
UCF 24
(15) Arizona 24 1st Qtr 1:11
Washington St 0
Texas-El Paso 6:00 PM
TX-San Antonio
Wyoming 6:00 PM
Colorado State
Syracuse 6:00 PM
(21) Clemson
Texas State 6:00 PM
ULM
(3) Ole Miss 6:15 PM
(24) LSU
(4) Alabama 6:30 PM
Tennessee
So Carolina 6:30 PM
(5) Auburn
(13) Ohio State 7:00 PM
Penn State
(20) USC 9:00 PM
(19) Utah
(14) Arizona State 9:45 PM
Washington
Nevada 10:59 PM
Hawaii
(2) Florida State 10/30/14 6:30 PM
Louisville
Troy 10/30/14 6:30 PM
Ga Southern
Cincinnati 10/31/14 7:00 PM
Tulane
Tulsa 10/31/14 7:00 PM
Memphis
Purdue 11/1/14 2:00 AM
(16) Nebraska
(17) Oklahoma 11/1/14 2:00 AM
Iowa State
Oklahoma State 11/1/14 2:00 AM
(11) Kansas State
(10) TCU 11/1/14 2:00 AM
(22) West Virginia
Texas 11/1/14 2:00 AM
Texas Tech
Northwestern 11/1/14 2:00 AM
Iowa
Maryland 11/1/14 2:00 AM
Penn State
Air Force 11/1/14 10:30 AM
Army
ULM 11/1/14 11:00 AM
Texas A&M
Duke 11/1/14 11:00 AM
Pittsburgh
Wisconsin 11/1/14 11:00 AM
Rutgers
Rice 11/1/14 11:00 AM
FIU
(18) East Carolina 11/1/14 11:00 AM
Temple
UCF 11/1/14 11:00 AM
Connecticut
Boston College 11/1/14 11:30 AM
Virginia Tech
North Carolina 11/1/14 11:30 AM
Miami-Florida
Washington 11/1/14 12:00 PM
Colorado
Central Mich 11/1/14 12:00 PM
Eastern Mich
Western Mich 11/1/14 1:30 PM
Miami-Ohio
Western Ky 11/1/14 2:00 PM
Louisiana Tech
NC State 11/1/14 2:00 PM
Syracuse
Texas State 11/1/14 2:00 PM
New Mexico St
Virginia 11/1/14 2:30 PM
Georgia Tech
BYU 11/1/14 2:30 PM
Middle Tennessee
Indiana 11/1/14 2:30 PM
Michigan
Florida 11/1/14 2:30 PM
(9) Georgia
Georgia State 11/1/14 2:30 PM
Appalachian St
Kentucky 11/1/14 3:00 PM
Missouri
Kansas 11/1/14 3:00 PM
(12) Baylor
Houston 11/1/14 3:00 PM
So Florida
(20) USC 11/1/14 3:30 PM
Washington St
Arkansas State 11/1/14 4:00 PM
Idaho
South Alabama 11/1/14 4:00 PM
Louisiana
New Mexico 11/1/14 4:30 PM
UNLV
UAB 11/1/14 6:00 PM
Fla Atlantic
(5) Auburn 11/1/14 6:00 PM
(3) Ole Miss
Arkansas 11/1/14 6:00 PM
(1) Miss State
Old Dominion 11/1/14 6:00 PM
Vanderbilt
Colorado State 11/1/14 6:00 PM
San Jose St
Stanford 11/1/14 6:30 PM
(6) Oregon
Tennessee 11/1/14 6:30 PM
So Carolina
Southern Miss 11/1/14 7:00 PM
Texas-El Paso
(7) Notre Dame 11/1/14 7:00 PM
Navy
Illinois 11/1/14 7:00 PM
(13) Ohio State
(15) Arizona 11/1/14 9:30 PM
(25) UCLA
California 11/1/14 9:30 PM
Oregon State
San Diego St 11/1/14 9:30 PM
Nevada
Wyoming 11/1/14 9:45 PM
Fresno State
(19) Utah 11/1/14 10:00 PM
(14) Arizona State
Utah State 11/1/14 10:00 PM
Hawaii
Los Angeles 0 FINAL
Seattle 2
D.C. 1 FINAL
Montreal 1
Toronto FC 6:30 PM
New England
Portland 7:30 PM
FC Dallas
Colorado 9:00 PM
Vancouver FC
Montreal 23 FINAL
Ottawa 17
Saskatchewan 27 FINAL
Calgary 40
Hamilton 21 3:00
Toronto 25
Brt Columbia 6:00 PM
Winnipeg
Hamilton 10/31/14 6:30 PM
Ottawa
Winnipeg 11/1/14 3:00 PM
Calgary
Brt Columbia 11/1/14 6:00 PM
Edmonton
Toronto 11/2/14 11:00 AM
Montreal
Connect with twitterConnect with facebookConnect with Google+Connect with PinterestConnect with PinterestConnect with RssfeedConnect with email newsletters

ADVERTISEMENT

ADVERTISEMENT

ADVERTISEMENT

 
Close