Instant MPG less than normal?

[DARTHSHO]

Im getting 19 combined highway and city if im doing 75 cruise control i can get about 25mpg
last tank im getting about 18 combined and im not driving any differently. so i just pulled the data its on my computer at home but the short term fuel trim was like 11.7% so its running lean and i think that has something to do with the increase in fuel usage. im running 87 octance and when i go on long trips or decide to do some racing i use 93 octane

 

[Yoder116]

Im getting 19 combined highway and city if im doing 75 cruise control i can get about 25mpg
last tank im getting about 18 combined and im not driving any differently. so i just pulled the data its on my computer at home but the short term fuel trim was like 11.7% so its running lean and i think that has something to do with the increase in fuel usage. im running 87 octance and when i go on long trips or decide to do some racing i use 93 octane

Interesting that you run 87 octane. I only get 91 where I live and run that all the time. I've also been sure to pay a little extra for no ethnol content from Signal, I've heard that help mpg's. What are you using to data log, and what type of tune do you have?

 

[DARTHSHO]

Forscan and its stock tune but it has the police calibration for transmission and pursuit mode. i think due to my last two tanks being 93 and then back to 87 i think the ecu is trying to compensate thats why its just dumping more fuel into it.

 

[b4black]

Im getting 19 combined highway and city if im doing 75 cruise control i can get about 25mpg
last tank im getting about 18 combined and im not driving any differently. so i just pulled the data its on my computer at home but the short term fuel trim was like 11.7% so its running lean and i think that has something to do with the increase in fuel usage.

It's not running lean. That's not how fuel trims work. It's holding the injectors open 11.7% more to keep the air/fuel ratio correct. Regardless of the fuel trims (within reason), it's running at proper (stoichiometric) air fuel ratio. It's not dumping in more fuel.

 

[FiveLeeter918]

It's not running lean. That's not how fuel trims work. It's holding the injectors open 11.7% more to keep the air/fuel ratio correct. Regardless of the fuel trims (within reason), it's running at proper (stoichiometric) air fuel ratio. It's not dumping in more fuel.

Yea it's not running lean until your AFR starts suffering beyond commanded. Fuel trims are just the correct factor needed to maintain commanded afr.

 

[skyshadow07]

I will chime in and say this is the first car I've owned where the window sticker numbers for city/hwy are no where near what I get. I have never gotten above 22mpg instant hwy and my combined is around 16mpg.

 

[High on Ethanol]

I get around 16 in city on e30+ nothing but Sheetz year-round. Usually get 23 or so on highway. I can't find a better gas around here. Never any pulled timing or any issues.

Sheetz e85 and Sheetz 93 FTW! I don't even mix accurately lol usually 6-7 gallons of e85 and the rest 93.

 

[skyshadow07]

Wish I was hip enough to know what sheetz means...

 

[High on Ethanol]

Wish I was hip enough to know what sheetz means...

An extremely popular gas station chain in a few areas.

 

[SM105K]

Normal driving on 91 octane 20/27 mpg.

E30 driving 13.5/20 mpg.

 

[luigisho]

Wish I was hip enough to know what sheetz means...

Like Wawa, but you don't have those either. Think big 7-11 but less crappy.

 

[yaycandy]

I caught up to low mpg