hooker2007

Low mile (90k) 2002 SS falling short of the advertised MPG.

19 city 28 city is what is advertised, but Im only getting 15MPG with mixed city/highway driving.

It has always ran 93octane.

I drive conservatively (never over 2500rpm, try to stay under 2000rpm), and only occasionally give more than half throttle.

SS FI hoodscoop
SLP Lid
Kooks longtube headers
Offroad Y-pipe
3" Cutout in Y-pipe
(Stock muffler, No cats)

Its literally the cleanest LS1 ive ever seen. The engine bay is showroom quality, and it looks like the block has been regularly cleaned and polished.

I need troubleshooting help on the low MPGs...

LS-ONE_DAY

A) 90,000 isn't technically *low* miles

B) Any engine lights/codes?

C) First place to consider would be bad Oxygen Sensor(s), start there. And check the plugs too. If one/more aren't helping to fire it'll just dump fuel without burning it, but that doesn't sound like your issue to me.

hooker2007

No codes... Wouldnt O2 voltage or misfires throw a code tho?

DANOZ28

iTrader: (1)

dont believe the 30 mpg people. 18-20 is average in the city & 25 highway. i've never driven in winter but if is cold i could see 15 mpg. check your plugs, wires, & tune. anything less than 13:1 A/F ratio could be hard on your milage. just my one cent.

hooker2007

How does one change fuel/air ratio?

jimmyblue

iTrader: (11)

Pretty much like my mixed driving gas logs. The MPG
did drop with mods. Long tubes mess up your low
RPM closed loop fueling and will tend to burn more
gas at idle especially. This can happen before you pop
codes, but with long tubes you (or somebody) ought
to have already been through heater, switching and
similar codes and "fixed" the reporting if not the
performance.

And then you can go merrily on your way never seeing
how annoyed or misled the PCM is about things.

hooker2007

Uh oh... A bunch of that went over my head...

Will a Diablo tuner help me do all of that?

DANOZ28

iTrader: (1)

i just have someone tune mine but you can try & use a tuner. i wanted to clarify that stock A/F is around 14.5:1 , i lost maybe 1-1.5 mpg after tune but i added rwhp. if A/F is 12.5:1 you'd be running too rich and losing significant gas milage imo. bone stock my A4 (auto trans) milage was 21.5 city & 24-25 hwy. now im 19-20 city - 24 hwy w 2:73 gears.

LS-ONE_DAY

I would get a "real" tune rather than a boxed handheld but that is my personal preference.

Mods will decrease fuel economy, if not themselves, but also because you tend to enjoy them while you're driving. Headers did lower my fuel economy a little bit, it was running rich, my tune helped with that. On the highway with my A4 2.73's I see 21-24mpg, but with the converter unlocked around town thrown in, mixed is like 18-21mpg.

You should see engine lights for misfires but just because you should doesn't mean you will. I had a bad coil on my DD and I could feel the effects of it several days before a light actually came on and started flashing.

O2 would scan it to see if there are any hidden codes, also, inspect the MAF, see if it is dirty/clogged

hooker2007

Best place to find a real tune?

Ill check the MAF screen asap!

demonspeed

iTrader: (7)

In my opinion, you tossed away anything regarding factory specifications when you began to modify it. That's not to say you can't have "good" mileage, but you can't be comparing your instance to factory-rated MPG. This is especially pertinent when you messed with the manifolds/converters/tune.

With that said, I do not, whatsoever, keep track of my mileage with my current car ('02 SS). It's purely for pleasure, so fuel mileage is of no concern to me (I also have long tubes, no cats/AIR, tune, etc.). On the other hand, my '01 Z28 (just a lid/catback - 90k miles) hit 30mpg on a fall highway trip through PA/NJ (this was back in 2003). I remember this because no one believed me that a LS1 could do that -- so I kept the gas receipts and mileage log.

DANOZ28

iTrader: (1)

i'll just add one thing i have road tripped in a 2002 bone stock 35th ann SS m6 from mpls down to racine wisc for the hot rod power tour and we calculated the gas milage at 25.5 mpg. the car maybe had 20k miles on it. cheers!

KissMyTushZ28

iTrader: (4)

I got 30 MPGs on the interstate cruising at 80 MPH in my Camaro Z28 6 speed with a tune! I get about 26 MPGs in my Trans Am now without a tune.

z28SSilvest

Dyno tune! And let whoever you have tuning it know that you want it slightly lean since you're worried about MPG.

BTW, to make power you have to sacrifice some MPGs but it's all worth it, especially when you can only see headlights never tail lights

14k

With longtubes dumped duals 3600 stall I managed to squeeze out 11mpg but im all city driving and I let my car idle til the gauge is about 130* every morning.

99z28monster

iTrader: (3)

No.

You would need an actual street tune not just a dyno tune for optimal results. Dyno tuning is great for the basics but to nail something down you need to log how the car performs normally and how it will be driven. Than you tune from that information.

garygnu

frost on this forum dose great mail order tunes .if you can find some local that dose street tunes ,check it out .

z28SSilvest

Street tuning and dyno tuning are basically the same thing except dyno is more accurate because the conditions are constant where on the street you have different types of ground (asphalt, concrete, etc) as well as wind conditions. I would never want a street tune only for that reason.

ss performance

iTrader: (17)

Several questions is it a M6 or an A4? I don't know the codes so I can't tell from the pic of you options.

If A4 is the converter locking up? And if it is it slipping?

How long does it take for the engine to get to temp? If the thermostat is stuck open the engine will take longer to come to temp. This will cause the computer to dump more fuel.

I would find someone with a scanner that can read all your sensors and make sure thay are reading properly. If could be something very simple. Start with the easiest cheapest first. Don't panic or assume that it's something major before you eliminate the simple things.

Good luck.

SSGunn

Mid teens in the city is normal for this car. Running 93 is better for the car but it does burn a little bit quicker than regular. I would be happy with 15mpg... I got around that when i first got the car but now with a few upgrades im getting about 12-13 at BEST