: MPG's slipping



jwall09
02-06-10, 12:07 PM
So i used to average 17.5-18.2 with balanced 50/50 highway/city. I have pretty much been 70/30 highway/city the last few months and im down to 15.1 mpgs.... Stock tune. Any ideas?

PGA2B
02-06-10, 06:57 PM
Part of it is Midwest (KC) Winter gas. They change the formula for less emissions becasue oil companies know you will let your car sit and warm up. It is the EPA that mandates it. It costs a few mpgs but not as much as what you are seeing. I typically see 2-3 less in the winter. Have it checked to see if the plugs may need to be changed and run some injector cleaner through it.

PGA2B
02-06-10, 08:59 PM
Also check the air filter. I would say check for gum up in the throttle body but since we can get to it.......

jwall09
02-07-10, 03:06 PM
Also check the air filter. I would say check for gum up in the throttle body but since we can get to it.......

Thanks and Thanks.

CIWS
02-08-10, 08:56 AM
Then try pulling your battery cable for 10 minutes and unlearn the car. :)

jwall09
02-09-10, 11:29 PM
Then try pulling your battery cable for 10 minutes and unlearn the car. :)

I just got a new ECM, so that shouldnt be needed, right? and the MPGs started slipping way before the ECM. I didnt need the ECM, but they were trying to figure out why my remote start locked me out of the car! hah.

PGA2B
02-10-10, 10:03 AM
I just got a new ECM, so that shouldnt be needed, right? and the MPGs started slipping way before the ECM. I didnt need the ECM, but they were trying to figure out why my remote start locked me out of the car! hah.

I don't think the new ECM is the issue. How many miles you have on her?

torched10
02-11-10, 04:01 PM
im getting 12mpg on car I bought in Nov.Its a 2008,no mods,18000 miles.Thats about what I was expecting--virtually all local drives,and the SC wants to come on in all gears at very little throttle movement.my 540HP Shelby gets the same,and it weighs alot less--so i figured its about right--are you guys getting alot better than 12

nlharter
02-11-10, 05:25 PM
I seem to get about 17.5 with normal driving, 50-50 hwy-city. On a long trip on the highway, I get 24-25. I like these numbers since my Avalanche gets about 13 no matter where I am driving.

torched10
02-12-10, 09:53 AM
I checked the MPG for a 2009 supplied by the govt for gas guzzler purposes and the STS V is rated 13/17---On my car, a 2008, if i scroll to the mpg spot on the info button, it says 12.2 for the life of the car--and your gettng 17--WOW!!

PGA2B
02-12-10, 10:25 AM
That sucks!! I get 22-23 hwy and 13-15 city. Of course that is without right foot extreme pressure!!

torched10
02-13-10, 08:33 PM
im new to STS V world---are the 206 and 2008 the same hp ad rear gears

BMBSALES
02-21-10, 11:44 AM
also don't forget the cold will run the engine leaner, and the ecm is going to compensate for that with trims...ie more fuel added. check it again in july...