What octane to use on the HHR
Thread Starter
New Member
Joined: 08-16-2007
Posts: 17
From: Hamilton
What octane to use on the HHR
Hi . Just got my HHR a couple of days ago. I was reading the owners manual and to my surprize GM suggests 91 octane fuel. My question is 
o any of you out there experience pinging or any significant performance problems running 87-89 octane fuel in your HHR's ? Keep in mind my HHR is all stock with no performance mods done at all. Your input would be really appreciated. Thanks .Paul
o any of you out there experience pinging or any significant performance problems running 87-89 octane fuel in your HHR's ? Keep in mind my HHR is all stock with no performance mods done at all. Your input would be really appreciated. Thanks .Paul
Senior Member
Joined: 04-19-2006
Posts: 457
From: Phoenix, AZ
Hola, and Welcome -
I've had my HHR with the 2.4 engine right at two years: While I wasn't surprised that Chevy suggested a 91 fuel, I've only done so 2-3 times, all closer to when I first purchased the vehicle. Since then, 87 has been all that goes in, and I have had absolutely no problems or pinging at all. Also, I did not see any noticeable difference in the MPG when I filled up with 87/89/91 octanes, either.
Hope that helps -
I've had my HHR with the 2.4 engine right at two years: While I wasn't surprised that Chevy suggested a 91 fuel, I've only done so 2-3 times, all closer to when I first purchased the vehicle. Since then, 87 has been all that goes in, and I have had absolutely no problems or pinging at all. Also, I did not see any noticeable difference in the MPG when I filled up with 87/89/91 octanes, either.
Hope that helps -
..........(knocking on wood now
Senior Member
Joined: 05-01-2006
Posts: 2,507
From: New London, CT USA
We seem to get higher PG on the highway with the 93 octane. The difference in MPG vs the 20 cent price difference comes into play here.
Still I usually go with the premium, but have not heard any pinging with regular . I figure Chevy may know what it is saying by recommending premium, but it is not in stone as it were.
Still I usually go with the premium, but have not heard any pinging with regular . I figure Chevy may know what it is saying by recommending premium, but it is not in stone as it were.
New Member
Joined: 04-23-2007
Posts: 26
From: nagera
For all you guys and gals that are using 87-89, just run about 3 tank fulls of 93 or higher and then see if you are getting the same mileage. I easily get 3 or more miles per gallon with 93 than with the other and the majority of my driving is city. I also tried ethanol for a few weeks, with no more success than regular 89. With all the electronics controlling these engines I doubt if you could get it to "ping". They just reduce the performance to the point the engine doesn't hurt itself.
Senior Member
Joined: 05-03-2006
Posts: 882
From: Newfoundland, Canada
To better undestand octane and how it may or may not affect fuel economy (as do sooooooooooo many things), here is some information.
http://www.api.org/aboutoilgas/gasol...ine-octane.cfm
I highlight this paragraph...
Gasoline with a higher heating value (energy content) provides better fuel economy. Traditionally, premium gasoline has had a slightly higher heating value than regular, and, thus, provides slightly better fuel economy, but it is difficult to detect in normal driving. There can be even larger differences in heating value between batches of gasoline from the same refinery, between summer and winter volatility classes, or between brands of gasoline from different refineries because of compositional differences. The differences are small and there is no practical way for the consumer to identify gasoline with a higher-than-average heating value.
http://www.api.org/aboutoilgas/gasol...ine-octane.cfm
I highlight this paragraph...
Gasoline with a higher heating value (energy content) provides better fuel economy. Traditionally, premium gasoline has had a slightly higher heating value than regular, and, thus, provides slightly better fuel economy, but it is difficult to detect in normal driving. There can be even larger differences in heating value between batches of gasoline from the same refinery, between summer and winter volatility classes, or between brands of gasoline from different refineries because of compositional differences. The differences are small and there is no practical way for the consumer to identify gasoline with a higher-than-average heating value.
Senior Member
Joined: 01-13-2006
Posts: 3,000
From: Superior, WI - Over the Hill Warranty Club member
I use 87 for my everyday driving and will use 97 on trips. This trip to the dells I used 87 and averaged 31.4 mpg, then compare it to one of my last trips with 91 that averaged 32.9.
The old saying goes that the mileage you get directly relates to what your pocket book can endure.
The old saying goes that the mileage you get directly relates to what your pocket book can endure.
Senior Member
Joined: 08-29-2007
Posts: 256
From: CenCoast California
There seems to be some misunderstanding about the 2.4 Ecotec in HHRs and octane.
GM recommends 91 because that is the octane which gives best performance. For about 20 years GM engines have used feedback control of spark advance. A "knock sensor" (KS) detects detonation and when the ECM "sees" a KS input, it retards the spark a degree or so. If the detonation goes away, the spark advance is held there momentarily then advances back to the base timing. If that level of "knock retard" (KR) doesn't stop the detonation, the EMC dials back the spark a little bit more, then "listens" again. This process goes on continuously whenever the engine is running.
Knock retard allows the HHR's engine to run on 87-octane with a spark advance curve optimized for 91 without detonation.
What's the tradeoff? Retarded spark under high load when running 87 octane.
The mileage difference? In a practical sense, this bit about high octane giving more fuel economy than low octane is B.S. Sure, there might be a very slight difference but to measure it would take some very precise driving and very accurate measurement of fuel flow, both of which are beyond the common method of reading the mileage traveled divided by fuel used base on gallons listed on the gas pump at fill-ups.
Also, the savings in mileage are probably negated by the increased cost of premium gas.
I only put 91-octane in mine when I know I'm going to run it real hard in warm or hot weather. Otherwise, I run 87 in cool weather and 89 in hot weather.
GM recommends 91 because that is the octane which gives best performance. For about 20 years GM engines have used feedback control of spark advance. A "knock sensor" (KS) detects detonation and when the ECM "sees" a KS input, it retards the spark a degree or so. If the detonation goes away, the spark advance is held there momentarily then advances back to the base timing. If that level of "knock retard" (KR) doesn't stop the detonation, the EMC dials back the spark a little bit more, then "listens" again. This process goes on continuously whenever the engine is running.
Knock retard allows the HHR's engine to run on 87-octane with a spark advance curve optimized for 91 without detonation.
What's the tradeoff? Retarded spark under high load when running 87 octane.
The mileage difference? In a practical sense, this bit about high octane giving more fuel economy than low octane is B.S. Sure, there might be a very slight difference but to measure it would take some very precise driving and very accurate measurement of fuel flow, both of which are beyond the common method of reading the mileage traveled divided by fuel used base on gallons listed on the gas pump at fill-ups.
Also, the savings in mileage are probably negated by the increased cost of premium gas.
I only put 91-octane in mine when I know I'm going to run it real hard in warm or hot weather. Otherwise, I run 87 in cool weather and 89 in hot weather.