Surferd15

iTrader: (20)

Read some posts about gas mileage but nothing seemed to fit. I drive my car daily and drive to work about 12-15 miles most on the highway couple miles city. So an average day maybe 40 miles. I drive conservitive and don't floor the car at all and I am getting like 210 miles on a full tank of gas. I am using 93 octane, I tried 89 octane and nothing seems to work better or worse. I replaced my plugs like 1000 miles ago, new fuel filter like 200 miles ago, air filter is clean, tires are about 36 psi...what gives?? I have no check engine light, I did have to replace one O2 sensor about 2k ago, drivers side front. I have a wait4metune to delete the rear o2s. Gas mileage before the tune seemed maybe a lil better but not much maybe 230 on a tank..I even have 2.73s.. Any suggestions? My car now has about 34k on it.

Tried Fuel injector cleaner and octane boost to maybe clean something but not much benefit at all.

RevGTO

iTrader: (12)

How many gallons at fill-up? I get the same number of miles on a 14 gal. fill-up - 15mpg.

shdybrady1988

iTrader: (3)

try seafoam first.

kenp

iTrader: (9)

That's about what I get. What makes you think there's a problem? Ah, you've read the posts from people getting 28-30 mpg in their modded ls1/ls6. If you want that kind of mileage you'd better buy a Mini Cooper S or Honda Civic.

JScamaro

iTrader: (6)

With mostly highway miles you should be getting over 20 mpg for sure. I average about 23 mpg with the mods in my sig.

ChocoTaco369

210 miles per tank is awful. There's something seriously wrong there. Stockish F-body's should get 100 miles per tank more than that.

Try Seafoaming your car. Also, go to Autozone and get a $7 can of MAF cleaner. Your MAF may be dirty, which could cause problems. You may want to consider changing the other O2 sensor, also. Usually, if one goes bad, the other going bad is right around the corner. You may not be throwing a code, but it may be on its way out, causing you bad mileage.

Also, a real dynotune would seriously help your situation, especially if you're running longtubes untuned. Since you never floor it, you're probably running pig rich, causing poor mileage.

bryan04h

iTrader: (2)

that is bad, how did the tune go on the dyno? could be sitting with a bad air/fuel ratio

jmm98LS1

iTrader: (28)

I wouldn't get too dramatic there choco.
While 210 miles per tank isn't great, it's unlikely you've got anything "seriously wrong" with your car. You've removed EGR and have bigger (heavier) 18" rolling stock, both of which can reduce mileage some. I've had my Z since it was basically new (6k miles), and bone stock with 3.23's I never got better than 20 mpg. Usually averaged ~17-19. Seafoaming & maf cleaning is a good suggestion. I'd also make sure you have fresh o2's, they don't last near as long when you've got longtubes. Lastly, with your intake/exhaust mods have most definitely thrown your tune a off. A correct tune for your mods will net you the biggest improvement IMO.

litle88

iTrader: (20)

I only have 35?k miles on my car and I have never gotten more than 220 miles per tank! STOCK
Then I got my cam in and the supporting mods in my SIG.
I still only get 210 220 miles per tank! Go figure.
My AFR is flat and steady at 13.

ArcticZ28

iTrader: (14)

Lucky! I get 12mpg

R1LS1

iTrader: (1)

I only get about 200 with the blower and other stuff on it. Of course I tend to have a little more "fun" then I used to

Daryn

iTrader: (19)

wish i got 200 miles to a tank.... hell even 150.. thrbo 350 with 4.10's and a big stall this car sucks gass..... when it was just a bolt on car it got about 300 to a tank

KyleLs1

i get between 320-370 KM to a tank (whatever that is in miles) with mostly city driving and the occasional hard run through the gears.

Highway driving Is much better cruising in 6th

cookba

iTrader: (10)

i get about 300 miles to a tank. after my headers, y pipe, Ported TB and tune where done i hot rodded and got 230 miles to a tank.

TX RED

iTrader: (19)

wow i get 265 270 every week with mods in sig and i do about 90 on the freway on my way to work every day

matt3383

iTrader: (3)

Well with the low miles you have i doubt the sea foam would do anything. I tried it on my car with 35k on it and i got a little smoke but nothing major.

Are you running synthetic fluids?
Im guessing the tune is hurting you A/F ratio some.

What is you cars RPM when your cruising?

Now I cant give you a very good answer since mine is a 2 spd car so i hope some auto guys can chime in here. I know my car with the 4.10s at 70 is under 2k RPM in 6th gear.

Around down im getting roughly what you are 210-220 per tank usually 13-14 gallons when filling up. But if i get on the freeway or highways at all it can shoot up to 20 mpg plus no problem.

ChocoTaco369

When a car should be getting 300 miles per tank and is getting 200 miles per tank, there's a big, big problem. He should be getting 50% better fuel economy. That is HUGE.

It's not a big problem to those who don't care about fuel economy. However, for most of us where fuel economy is important, it is a huge problem. If these cars got 50% less fuel economy, most people on this site would not own them. I know I wouldn't own a 13 mpg car. My car gets 22 mpg in the summer, 19 mpg in the winter with 50/50 driving all the time.

CAMAROZ28AQUINO

welcome to the club

Ericbigmac83

iTrader: (19)

lol, gotta love the gas sucking 408

I find that people really enjoy being around my car as i sit in rush hour traffic on the beltway...

ArcticZ28

iTrader: (14)

I feel sorry for anyone behind me in traffic. Hell, I actually feel more sorry for myself, to be honest. The consequence of my need for power is an acute loss of brain cells at stop lights. If they hadn't been destroyed already, I might have thought to do something about it.