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Right now I'm about 270-odd miles into a...sit down for this...32.0mpg tank. What's worse? That's at least 80% highway mileage, and the last tank (a short-ish fill in anticipation of extended driving) was short of 35mpg range and also 85+% easy highway mileage. WTH? Under these conditions I should very easily be in the 36-38mpg range like I was in March or April. The instant ScanGauge readings agree with tank calculations, indicating that the car is working much harder than it normally would under given conditions. (It doesn't exceed the 40mpg barrier at a flat 65mph cruise, which is unheard of. Things are also much worse under high load, such as hills that I climb frequently.)

Coast-down seems about right, so I can't find any real indication of a dragging caliper or other source of unusual drag. So either the engine is screwed up, or else it's the gas: these last two tanks have been Citgo, which I have not used since I started recording mileage. I figured I would give it a shot since they have the best prices in town, if not the state. I have never really bought in to the hype about brand of fuel mattering, but this kind of thing makes me wonder.

Could a faulty or clogged EGR valve cause this kind of thing with out tripping the CEL?

My first guess would be the fuel. I found on Citgo's website that they do add alcohol to thier fuels in certain markets. This, coupled with the cooler temps(in my part of the country anyway), and your numbers look believable. Looks like it will be a long winter.:(

I say it every time, but have you checked your tire pressure?

As for the EGR. When I replaced mine no code was shown. It helped by about 5mpg.

I would really think that the problem is just that we are getting in to winter. BTW, I won't use Citgo anymore since all the money goes to that nut down in South America.

I double checked the tire pressures, which were at 42psi all around and have been bumped back up to 45. Not too low. Double checked for codes with the ScanGauge and couldn't find any. That leaves a "quiet" engine malfunction and the gas. Like I said, the 32mpg number is believeable but not consistent with my records. At the end of march and beginning of April I was pulling in 36 and 38mpg tanks with dayime highs in the 40s and 50s F, which is perhaps a bit cooler than what I'm seeing now.

Unless someone has a better idea, I guess I'll run this tank down to the bottom and fill it up at the Shell station that was working for me before I discovered the cheaper stations in the other part of town. If that doesn't give some improvement I'll start looking for electronic or mechanical faults.

hm when i traded my car he said my car was ROUGH.... i guess all that fasing really murdered it hehe.... glad I traded it immediately!

hm remember temperatures kill! have you blocked your grille yet? cardboard is free!

Hi Brick

Take a look at my post regarding resetting KAM in the FEH. Second paragraph I speak about Citgo gas before you posted. I will not go near a Citgo station, even before the Hitler of Venezuela sided with the axes of evil.

http://www.cleanmpg.com/forums/showthread.php?t=2463

GaryG

Hi Brick:

___Citgo or not (Tom and I are stuck with Winter RFG based E10 in Chicago too), I have 3 tanks still to upload since the Insight Marathon attempt and none are even close to 50 in the Accord. My latest SG-II commutes are down in the 45 - 48 mpg range and yes, the colder temps are killing us! I had one day last week where it briefly touched 60 degrees F on the way home. She allowed me a 54.7 for that 90 mile segment! You can almost see the increase in FE during steady state cruise, longer glide distances, and acceleration rate FE increases as you pass through 45, then 55, and the up near 60 degrees F … These high 20 to high 30 degree temp mornings and nights are truly FE killers :(

___Good Luck

___Wayne

:cry: :(

Gary, good post! I must have missed that one. I was wondering how the ECU comes into play and you have explained it quite nicely. It might be worth a reset after my next fill. I was under the impression that all gasoline in CT contains a fair amount of ethanol so I didn't think brand would make much of a difference. (I'm aware of the politics, but let's face it: the vast majority of gasoline purchases help finance somebody who hates us.) Anyway, I'll add a KAM reset to my next fillup.

Phil, when did you get a Prius? Congrats! I doubt the Civic would be "rough" due to FASing. Maybe a little carbon buildup from constant low-load, low RPM driving? Nothing a little "Italian tuneup" can't fix.

I'm working on bringing it back...slowly. I'm about 300 miles into this tank now and have brought the average up to 32.3mpg after a couple of OK commutes and one really, really bad one. Today I switched over to the "current" function of the ScanGauge to watch how the average changes as each trip progresses.

The warmup penalty is obvious, as I didn't even reach double digits until 1/4 mile into my drive this morning (35 or 40 degrees F). Don't even ask how long it took to break the 20, 25, and 30mpg barriers. I'm not sure how I feel about implementing a warmup P&G to get her loose but I certainly see how it would come into play.

Another thing I noticed is that the benefit from coasting is about the same as it always has been, but the penalty during acceleration is just unreal. Even after 15+ miles of driving. You're probably thinking "Well, duh! That's when the engine is burning the fuel!" But it helps to have seen it on the instrumentation because this justifies and quantifies the feeling that car is extremely sensitive to operator error...it is. A set of scew-ups that would have brought dropped the milage from 40mpg to 38mpg for the trip in warm weather is now worth a drop from 36mpg all the way to 31 or 32mpg. Setting the cruise at 60mph doesn't work anymore!

But this is good, because understanding the dynamics a little better should help re-claim some lost ground. I'm trying to dig a little deeper in order to minimize the behaviors that weren't so bad before but really hurt now. I still believe that the gas thing is a contributing factor, and hope that the FE:Effort ratio will swing back just a bit on the next tank.

Ahh, driving is so much simpler before you start paying attention to this stuff!