I know the LS1 can get 30+ mpg, but for some reason im only getting an avg of 23mpg at 65mph

i have I/H/C/ and full exhaust, that stuff isint supposed to reduce MPG.... so what should i look at?

filter is clean...

 

o2 sensors, plugs + wires, fuel filter... is your car running ok?

You're saying that if you reset your avg fuel economy and cruise at 65 on a level road, you will average 23 MPG?

 

I find that if I think about getting good mileage, I will get good mileage, and if I drive like the car makes me want to drive, then I get 25mpg max. I have averaged over 31mpg combined when really trying, and as little as 10mpg combined when I drive hard and forget about sixth gear.

 

I see that you've had your car "tuned." That could be the problem-----not all tunes are created equal.

If you can reflash to stock, you might want to try that.

 

it wouldnt run right if i reflashed to stock, ill swap out my o2's but im not running rich or lean... right between 12.5 and 13 all the way up the power band

and yes i reset and cruise at 65... and never get better than 23mpg

 

I've been averaging around 23-25 on day to day driving and then 30-31 on long trips. This is calculated manually when I fill up, not relying on the readout.

What is your average when manually calculating it? You may just have to have new tune done from scratch. I would think it should be better than what you're getting. My C4 gets better mileage than you're seeing.

 

How are you measuring A/F? A/F could be good on the dyno at WOT but off at part throttle and cruising. You would need to either to data log while cruising on the street or run it on a load dyno.

 

yeah im not happy about the MPG

I havent done the Manual calculations since i had the digital readout... ill do it on this coming tank

the A/F is coming from a tube stuck in my exhaust sitting on the dyno

 

I can easily get over 30 mpg on the highway.

 

what's your differential gear ratio?

 

What cam. They can hurt fuel effiency a bunch


with the current mods in my sig I have gotten as much as 33.2 on a 170 mile trip!


Clean your MAF and everything else!

 

ill get some intake cleaner and hit it all up, what speed were you sitting at when you got 33.2mpg?

im running a 226/228 Doug rippie cam

 

There are a lot of factors that go into average mpg - traffic conditions, terrain, throttle position, gearing, headwinds, etc.

When I drive all freeway and keep it in sixth on level ground, and most importantly maintain a steady speed - I average in the high twenties almost thirty mpg. When I drove the car home from Chicago when I bought it - my 2000 mile average was 29.7 mpg. But a mix of highway and city driving, with traffic etc, realistically I average in the low twenties.

It still gets better mileage than our other car - and when I factor in the fun per mile and smiles per mile, I figure I'm doing just fine.

Check your tune and all that - but you need to look closer at the conditions over which you have little control as contributing factors.

 

i got the 23 on a level 350 mile trip, very slight hills every now and again

what speeds are you guys at?

oh, and stock gearing

 

Best way to measure highway mileage is on a long trip, one that takes several tanks of gas. That will remove any varables.

On my '04 conv auto, pure stock, I got 30.5 on a trip from central Texas to Las Vegas and back, total of about 2500 miles. And that was cruising at 75-80 mph under cruise control.

tom...

 

^^^Your car looks prefect bone stock



I get 19-21 with 50% city 50% highway.

 

Most report their highest mpg at or above 70mph. This is probably due to the tall gearing of the MN6 and aerodynamics.

My highest long-trip mark was 32mpg and it was with the cruise set at 75mph.

Good luck on finding your problem

 

I average 32 mpg with my stock 02 coupe with automatic. I must add that I drive 5 under the limit on highways. That is the average that I have gotten over the past several years.

 

my 6 spd used to get 30.5 on long road trips, now it gets 26 with the mods

 

I've only had my 04', C5, Auto, Vert, grocery getter since the middle of December but my daily commute to and from work is about 30 miles each way on US-95 north from Vegas. It's a long, strait, relatively flat road with a 70MPH speed limit and lots of cops who love pulling over speeding GI's and writing tickets. I normally set the cruise at 75mph and flip the DIC to instant MPG so I can watch what the car is doing. On perfectly flat level road the average is about 28-29MPG but every time I hit any kind of slight uphill in the road it drops to 23-24MPG and on any slight downhill it goes up to 32-34MPG. With about 70% highway and 30% around town driving the best I've gotten on the DIC's average MPG readout for single tank of gas is 22.8MPG. On a long highway drive of a few hundred miles over several tanks of gas I could easily believe a 32MPG average per the DIC.

Do my numbers sound about right compared to what everyone else is getting? I've been toying with the idea of taking everything apart and cleaning the heck out of it just because I don't know how well the previous owner maintained it. I figure it wouldn't hurt to do but I'm a bit paranoid about ripping such a beautiful machine apart and not being able to get it back together. Heck I about had a brain hemorage trying to instal a K&N filter How the heck do you get the assembly out to put clean it and install the gasket without breaking the tie down straps?

Even if the best I ever average is 22.8MPG it still beating the heck out of the milage I was getting out of the 06' Quad Cab 4x4 Tacoma I traded in on it. The absolute best that thing ever got was 24MPG from L.A. to Las Vegas.