ugh now what fun is that hehe

 

I used a Fram air cleaner filter, Bosch Platinum Plus 2 spark plugs, Mobil 1 5-30 synthetic oil with a Fram CH9018 oil filter, fuel system cleaners in each tank of gas, 40 psi in my tires, and I put it in nuetral when I am going down hill, I get about 33 mpg. My car has 25,000 miles on it. Trust me, these changes needed to be made to improve the gas mileage and the performance.

 

Fram filters aren't exactly known for any quality these days. Well documented.

The Bosch multiple electrode plugs aren't the best either and are inferior to the newer Iridium plugs, such as the OEMs.

GM does NOT recommend fuel additives. The mandated additives today are fine.

40 PSI may lower rolling resistance slightly but expect a harsher ride and more wear in the center of the tread as a result.

Putting the car into neutral going downhill is useless, in fact will result in LOWER mileage. When in neutral, the ECM is still providing fuel to prevent a stall. These newer cars have a programmed "feature" called DFCO (Decelleration Fuel Cut Off) that will cut off all fuel during most coast down conditions. It is done for both fuel mileage and emissions.

 

Then why does the mpg's go up on the DIC?

 

Some thoughts to ponder....

1. Put car into neutral: Gas is fed to prevent stall. (not much though)

2. Leave in gear: NO gas during DFCO, where NO gas is fed.

Now which do you think uses more??

 

But if no gas was fed, wouldn't it stall?

 

Yes it would. However below a certain RPM or speed in gear, the fuel will resume to prevent a stall during coastdown.