Mileage vs Octane Level - Road Testing

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01-26-2009, 06:18 AM

#41

pitbull76

Senior Member

Join Date: 11-20-2006

Location: Peoria, IL

Posts: 931

Quote:

Originally Posted by The Curly 1

Your 2.4 does not need the higher octane and probably would not benifit at all with it. The 2.0 Turbo on the other hand is designed to run on the higher octane and it does need it. The higher octane helps prevent knocking and the spark retard that hurts mileage and peformance.

The 2.4 DOES recommend using premium for optimal performance. Check the owners manual. In my old 2LT, I could notice a slight perf increase with premium, but never noticed any mileage bump. The 2.2 is the only HHR motor not designed to take advantage of premium fuel.

01-27-2009, 06:00 AM

#42

The Curly 1

Senior Member

Join Date: 03-08-2008

Location: United States of Texas

Posts: 505

I think my 2.2 does not require premium

I think my 2.2 does not require premium. If the 2.4 is designed to use it then your best mileage and performance will be with the gas it is designed for.

01-27-2009, 08:34 AM

#43

catdaddy137

Senior Member

Join Date: 12-20-2008

Location: durham north carolina

Posts: 835

28.69 mpg today

Quote:

Originally Posted by catdaddy137

i found absolutely no increase in mpg at 72 mph average . correction - the fuel i added was 93 octane - 20 cents more per gal. i think i will continue testing for about a week. from watching my dash i think there may be a 1 mpg increase at 55 - 66 mph , but it did not show in the overall average. if i could get 2 more mpg without slowing , i may break even on the extra cost. it doesn't look good so far. the temp was 50 deg. the humidity was a little high. i may even add some octane booster just to see if i get any effect. also i had 39 psi -warm- in the stock 17 firestones with 42000 miles. 26.73 mpg today. as i stated i have the stock ho 08 2.4 panel. others may have different results. let us know.

my dash dic thingy says 28.1. $3.11 more than reg gas would have costed for 15.575 gals. i will continue testing. if i cannot get more than 2mpg increase , i will not break even on the cost. also i did up the psi in my tires 39-40. the temp was 40 deg, and i did some 55mph where i ussually do 66 , at least 25miles. also found that 73mph is better than 72.

02-05-2009, 12:35 PM

#44

Canuck

Senior Member

Thread Starter

Join Date: 04-19-2008

Location: Ontario Cdn

Posts: 563

Quote:

Originally Posted by monster5601

It would be interesting to know the association of air temperature an fuel octane during your tests. It has been my experience that in colder temperatures, lower MPG are obtained. For example, I always use 93 octane fuel from the same brand. When temperatures reach down in to the 20's I loose about 3 MPG compared to air temperatures in the 60's and on up.

Hmmm my impression is exactly the opposite, excluding the huge loss when driving in snow. I had attributed it to the condensed gas and particularly the condense air (a.k.a Mother Nature's inter-cooler) for the improvement in cold weather. Again only when the roads are bare and the car warm (long trips) otherwise I agree, my winter mileage is absolutely terrible.

That said most of these reports were taken in the low 70 to high 60's (plus or minus a few degrees variance, day to day) - which to us poor Canadians is like summer.

02-06-2009, 05:22 PM

#45

jerSSey HHR

Senior Member

Join Date: 07-03-2008

Location: jerSSey, exit 5

Posts: 1,664

I can't seem to get any sustained increase in MPG going from 87 to 93 octane. But there are so many variables with this crappy winter weather.

04-06-2009, 07:51 PM

#46

hhrsscanuck

Member

Join Date: 01-30-2008

Location: Canada

Posts: 59

Quote:

Originally Posted by esmarkey

Thanks Catdaddy, I am also interstested in seeing Cannucks results.

Howdy,

As a previous owner of a 2007 2.4L HHR LT (5 spd), the best gas mileage I ever achieved was during a trip to NYC/NJ/DC in Sept 2008.
7.2L / 100kms! Average speed was 105kmph roughly 65 mph. This was running 91 octane. On average, if I ran 91 octane, I got an extra 50-100 kms out of a tank depending on speed, and acceleration was not compromised. 87 or 89 just lagged under the gas pedal. I think that record trip on one tank came to 800kms+... somewhere in that number.

I picked up a GM Exec 2008 HHR SS (5spd) a couple of weeks ago (came from Michigan). I drove that home from Ottawa, averaging anywhere from 100-110kmph (roughly the same as the US trip) and achieved 8.1L / 100kms.
Now.. this being said, I did get stuck in traffic in Toronto and did enjoy throttling on to the highway over and over again, so I skewed my results.

During the trip, the HHR was reporting 7.x / 100 in the 'immediate' mileage menu option, so I do believe it's possible to get it down to 7.x if averaging 80-110kmph during the whole trip.

As to why the dealers kept telling people to run 87 / 89 in their tanks when the manuals said to use 91 only boils down to gas cost fear.
The guy who took my LT away looked a little nervous. I told him he'd get his savings back in more mileage and better power. I tell folks who use the 87/89 gas about my mileage record and they rethink their choice pretty quick.

Rob
Kitchener, ON, Canada