I have an '08 2LT 2.4 and have been getting on the DIC 30.2 70/30 hwy/city, and its got 25K miles on it now. I dropped in a K&N filter and removed the flex hose and now it has gone to 33.4 same 44 mile round trip. I got rid of my 07 Dodge Caliber, it was a nice car but only averaged 26 on that same daily trip. I'm very happy with my HHR, better mileage, more people room, more luggage room, what's not to like..

 

So, what exactly RPM should I be seeing in a 2.2 going 70mph? It runs around 2500, and that just seems high to me, but then again, I've never had a 4 cylinder car...so I don't know.

 

I can honestly say my mileage is going up. Took my family of six to Sun Valley Idaho today averaged 36.4 mpg on trip. I have a 09 LT2 with 4600 miles on it now...

 

How did you get six in a HHR?

 

i find that i get better mpg when it rains or the air is moist....some people claim increase mpg with diy hho ...i don't think moist air is the same thing , but i am really not sure....i believe that when people modify their vehicles for mpg , some probably drive a little differently , trying to fool theirself into believing that they have done some good....but as long as they are not trying to sell something , i believe some of the claims...is moisture in the air and hho the same or kinda simular ?

 

moisture in the intake is the same as the cooling spray tents at the parks,,,, it cools the incoming air making it denser....also since water does not compress it acts like a compression increase...which makes for a good top eng cleaner as it acts like little soft marbles and knocks the carbon loose,,ever see a cylinder with a blown head gasket? Spotless...

 

There are two bolts in back for the latch system, I bolted in a seat belt there and my children fight over who gets to ride back there, we also have a pillow to help with confort, will post pics soon....

 

water injection and hho are 2 different things ?....i know a mechanic that had a home made water injector 20 years ago , long bafore i heard of all this hho hydrogen stuff.....if i remeber right , it was just a mayonase jar with some water in it , and a small tube going into some part of the intake air...i didn't totally understand it then , and i still don't....but i do believe there maybe some benefit from it.

 

Hey, neat idea.

 

Those are not designed to hold it's own seat. But how did you secure the other two corners of the seat?

And you let your kids ride back there?