I have just purchased my second HHR and got the 2.4 this time up from the 2.2 and wanted to know if i have to use premium unleaded or just regular and if it doesnt matter if i use premium or for that matter the E-85 will i get more spunk???? Also can i add E-85 to a half a tank of regular unleaded will it hurt the car?????

 

You don't need to use premium fuel in your HHR, it is just recommended mostly for performance I think. Using regular fuel won't hurt the engine or anything; you just might notice a decrease in acceleration. I have the 2.4L engine in my 2007 HHR, and I go back and forth between premium and regular fuel, but I don't really notice much of a difference between fuel types. I think the only time you'd really notice a difference is if you drive your HHR like a racecar. As far as your E-85 question, I don't know the answer. My HHR isn't Flex-Fuel, so I don't have any experience or knowledge about that.

 

Mine's not Flex-Fuel either but if your car can take E-85 there's no problem mixing that and standard unleaded.

On the octane question.... I use premium by choice (It's recommended or optional on my '07) and it runs much better and gets better mileage too...... Yes, I drive it like a "racecar" up to speed limit then cruse.

The engine is designed to adjust to the fuel octane so with regular it turns the timing back along with other adjustments so it doesn't knock and damage the motor, (The 2.4L is a very high compression ratio motor so would be prone to knock without the computer controls) premium it cranks the timing up for more horsepower. If you were running in the range where you use the extra horsepower the engine is very efficient so it can actually get better mileage. In my case I think the cost difference is compensated by the extra MPG, doesn't hurt that it's a blast to drive with the premium either.

 

I have a 2007 and so I can't use E85. E85 has higher octane and gives lower mileage. I have always used regular unleaded in my 2.4 with no problems and plenty of acceleration with the manual transmission.

 

i did a bit of testing with my 08 with some premium this spring. I really didn't notice any gains in mpg and if any in performance they were quite small. I had been running regular since I bought it and switched back after a few tanks of premium.

I know weather, temp, everything has a lot to do with it, but if I remember correctly I even had the premium in when i went to see my parents, which is a 6 hour drive. After checking the mpg when the tank was done, it wasn't higher then any other time, and lower then some of my drives. I have gotten a 31-32 mpg avg on that drive before on reg. I record my mpg on every tank of gas that pretty much has been in the hhr since i bought it, even designed my own gas book.

 

You can use whatever you want; it's up to you. Going with premium fuel can't hurt anything, but it just costs extra $$. But you get more power with premium too, so it just depends on what you want. When gas prices are higher, I usually stick with the cheapest gas possible. But when gas goes down, I start using premium more often. Either way is fine.

 

I don't think you would see a MPG difference with mostly highway driving unless it were hilly, needing the added power.......

 

I do alot of driving 50 k plus a year and love my hhr a lot of the driving is in Colorados Mountains up and over the passes of I-70 etc. I actually just purchased the new HHR after a trip to the other side of the state and was terribly disappointed with my old HHR (2.2) so i decided that since i just about had the other one paid off i would get the 2.4 and i am really hoping that i have better power.

 

carmanrick-

What year is this HHR w/2.4 ?

My 2.4 is in my '08 panel, so I can't (or wouldn't even want to use E85).. I like getting 100% gas..
That in my ride runs the Best & gets the best mileage also..

And mine is certainly no slug..

 

I thought I was bad putting on 25,000-30,000 miles a year. I felt like I was putting on excessive miles. Now I don't feel so bad.