What exactly does that tell us? You fill up every 200 miles, but how much fuel are you putting in after 200 miles? What is your average mpg?

I get about 23 mpg on a 98 5-speed with 100k on the 3.8L motor.

 

my 3.4 only gets about 18 mpg in the city and 22 or so highway. what can i do to increase this. i already have new plugs and wires, air filter, o2 sensors, and cat. any other suggestions?

 

96 auto, Drive 104 miles round trip to work. 90% freeway. 65 to 70 on the cc.Fill up after 3 trips, 26 to 28 for the last year. Seafoamed 2 weeks ago and last tank was 29.6. 160k on the clock. Best ever on a trip to Fontana 2 years ago, cruise set at 80 on I5, 33.6mpg.Gonna get headers, new high flow cat and Magnaflo CB see if I can get 30.

O2 sensors replaced last year. Maybe its just a fluke or it was built on Wednesday?

 

Ok, tried a tank of mid grade on the way home and averaged another 27.9 mpg tankful, wife drove a bit and but while I was driving, CC was set @ 75 mph with the air on.

Only mods to the car is an Amsoil multi-layer foam air filter, Flowmaster cat back exhaust and a home made restrictor plate for the EGR valve.

 

i fill up at 300 miles and it 10-11 gallons. thats 28-30 mpg, 114k on the car

 

i got a 97 v-6 3.8 min. mods with about 117k and i get about 350-400 miles fill up...gas here in va is round 2.71 so about 35 buxs to fill up

 

So what is the function of the home-made EGR valve restrictor plate? Have a picture?

 

Get a CAI... But there is some other problem -- try Lucas injector cleaner...

 

2x^^

 

As we all know, the EGR valve reduces NOx emissions by introducing some exhaust gas into the air/fuel mix. On the '01 Emission system, the EGR also acts as a throttle positioner during deceleration reducing HC and CO emissions.

As I understand, the EGR valve needs to be caliberated if it's been replaced. I could be wrong, but that's what I heard. After replacing my EGR valve I was experiencing a lean surge at 45mph indicating the valve was opening too far. I used my scanner to determine how far the valve was open when the surge accured. I wasn't about to pay Chevy to recalibrate the emission system. So the purpose of the restrictor plate.

I used a gasket for the EGR valve as a template and made the plate from 3/16 stainless steel. I drilled the hole for the exhaust at1/4" and the intake side hole at 5/16". Consideribly smaller then the 12mm or so mainfold opening. The plate goes between the manifold and valve with a gasket on each side. No, I didn't take a pic of it.

I tried blocking off the valve totally, but every time I decelerated the computer would throw a code (forgot the number) 'EGR Valve Not Opening'. Now, no code on decel and no surge at steady light throttle. And as we know, too lean is just as bad for mileage as too rich.