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Well, here's the sum total. On my trip last Saturday with real math, not the DIC, I got 18 MPG over 250 miles. Now that included about 8 hard charging laps on a 2.15 mile race course. The rest was highway miles, about 250 of 'em. On my way there I probably averaged between 75-80 MPH, on the way home probably averaged around 75. In my mind, that just seems like a pretty low average for the whole trip even keeping the "racing" portion and my modest mods in mind especially given I've been able to pull down 30mpg in the past with a not drastically different version of the car.

Anyway, the tuner will be able to tell me if the cruise values in the tune are out of whack a bit. If not, it just is what it is.
i always got worse mileage on my 05 than i do on my 04, by a 2-3 mpg.

to boot, you'll get better if you drive a tad bit slower. i find 55-65 tends to yield the best gas mileage.

honestly, i don't think you should get much different than stock. you might just have the foot down more with all of your new found all moda powa. (sorry i felt like cheeese.)
 

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IIRC, and this goes back to 05, I vaguely remember anything over 65mph would hurt MPG’s.
 
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Discussion Starter #23
So, we went to Omaha to have dinner and ****tails with friends. About 80-85 miles round trip. About 90-95% highway. Drove about 1/3 of the route at 75 and the rest at 65 or slower other than the little bit of city driving. Started on a full tank and reset all the calculators when I filled up. The DIC says barely into the 19s and past experience has told me that it is always optimistic so I'll bet I got 18 or worse. No hot rodding at ALL since the wife was in the car and she hates that stuff. Right or wrong, something is dramatically different from before the professional tune to after the professional tune. A trip like we took tonight in the past would have had me in the 23-24 range easy (on the DIC at least).

Fuel is the same fuel from the same place, 91 octane no alcohol, top tier.
 

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I'm surprised to hear people got more than 25MPG with the LS2. I've never seen over 26 with highway cruising over 60 or 65MPH.

As was stated before, Lean Cruise is only available in 04 LS1 ECUs and isn't enabled on North American "Monaros" because of emissions (too much NOx). Lean Cruise doesn't have tables in the LS2 ECU.
 
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My '87 Camaro had lean cruise (as well as DFCO and a rev limiter) but they all had the values set so high that they were never enabled. I used and tweaked all of them to my liking, and I could knock out 24-25 mph on the highway with a 385 (224/230 cam, TFS heads, StealthRam intake), A4, and 3.42 gears. I think I had the lean cruise set to 15.7:1 A/F ratio.
 

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I'm surprised to hear people got more than 25MPG with the LS2. I've never seen over 26 with highway cruising over 60 or 65MPH.

As was stated before, Lean Cruise is only available in 04 LS1 ECUs and isn't enabled on North American "Monaros" because of emissions (too much NOx). Lean Cruise doesn't have tables in the LS2 ECU.
id bet if i slowed down to 60-65 i could easily pull 26 on the highway. i get 24 doing 75-80 over a 4hr highway drive
 

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LS2's just didn't get the MPG that the LS1 got. Best I got in mine was 33mpg way back in '05. That was with lean cruise enabled. Best I could get after doing mods was 29-30mpg. Combined usually stayed around 23-25mpg. '04's are nice that we can do lean cruise :)
 

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I got 24 mpg at 75 mph highway when I bought my 06 M6 in 2008, and I still get that 12 years later. I can't comment on track mpg for this car, but my 77 Ferrari and my 89 Porsche both got 7 mpg on the track. The Ferrari got 17 highway, and the Porsche got 30 highway, but both got 7 on the track; both weighed about the same and had about the same horsepower - ~ 240. The GTO weighs 800 lb more and has a lot more hp; I'd be amazed if it got over 5 mpg on the track.
 

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Discussion Starter #30
So, I visited the tuner yesterday. He bumped up the timing a bit and set the cruise table cut off to be around 2500. Before it was set so low I was getting out of the cruise table at RPMs equal to anything over about 65-70 on the highway. It started raining today and is supposed to keep up through Sunday so I don't know when I'll get a chance to test the MPGs. Driveability and power are the same. The DIC MPG reading bumped up from 18.8 to 19.4 on the 10 mile drive home, it didn't move a bit on the drive there, FWTW. I'm also thinking I'm going to change back to getting gas at my old station. It kind of dawned on my that my mileage on the GTO and the daily went down somewhere about the time I started using a new station (both were tuned about the same time so who knows) and I have to wonder if the new station is selling their 91 as straight gas even though it might really be E10. I know tinfoil hat thinking, but it easy enough to switch back to the old station and see what happens.

The tuner did mention that a lot of stations still have Winter blend gas in their tanks since folks have been driving less due to CV-19 and that 91 octane gas typically sells even slower than the 87s and 89s so there may be some truth to that. Winter gas could definitely explain some of the drop off in mileage.
 

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i've always wondered if the seasonal blends truly affected mileage. winter should be more volatile... maybe you're just loosing it to vapor, lol.
 

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Discussion Starter #33
At this point it is all academic, the tuner wants to know what comes of it all. Didn't even charge me for the update. Said he'd change it right back if I notice any problems.
 

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So, I visited the tuner yesterday. He bumped up the timing a bit and set the cruise table cut off to be around 2500. Before it was set so low I was getting out of the cruise table at RPMs equal to anything over about 65-70 on the highway. It started raining today and is supposed to keep up through Sunday so I don't know when I'll get a chance to test the MPGs. Driveability and power are the same. The DIC MPG reading bumped up from 18.8 to 19.4 on the 10 mile drive home, it didn't move a bit on the drive there, FWTW. I'm also thinking I'm going to change back to getting gas at my old station. It kind of dawned on my that my mileage on the GTO and the daily went down somewhere about the time I started using a new station (both were tuned about the same time so who knows) and I have to wonder if the new station is selling their 91 as straight gas even though it might really be E10. I know tinfoil hat thinking, but it easy enough to switch back to the old station and see what happens.

The tuner did mention that a lot of stations still have Winter blend gas in their tanks since folks have been driving less due to CV-19 and that 91 octane gas typically sells even slower than the 87s and 89s so there may be some truth to that. Winter gas could definitely explain some of the drop off in mileage.
All stations, unless the pump is labeled as ethanol free, sell E10. Label on the pump will even say contains up to 10% ethanol.
I got the local Arco station in trouble. Filled up and the ethanol content gauge in my car showed 15%... contacted the state and they did a check, right out of the pump was 21%... my 1/4 tank diluted it to 15 for my gauge. They were fined and were closed for almost 2 weeks after that
 
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All stations, unless the pump is labeled as ethanol free, sell E10. Label on the pump will even say contains up to 10% ethanol.
I got the local Arco station in trouble. Filled up and the ethanol content gauge in my car showed 15%... contacted the state and they did a check, right out of the pump was 21%... my 1/4 tank diluted it to 15 for my gauge. They were fined and were closed for almost 2 weeks after that
yikes.
 

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Discussion Starter #36
All stations, unless the pump is labeled as ethanol free, sell E10. Label on the pump will even say contains up to 10% ethanol.
I got the local Arco station in trouble. Filled up and the ethanol content gauge in my car showed 15%... contacted the state and they did a check, right out of the pump was 21%... my 1/4 tank diluted it to 15 for my gauge. They were fined and were closed for almost 2 weeks after that
All the pumps that are not 91 are labeled E10, the 91 pumps are not labeled as such. I just suspect they may have some version of E10 in their 91 pump. I think there is an easy way to test at home, I'll have to look into it.
 

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All the pumps that are not 91 are labeled E10, the 91 pumps are not labeled as such. I just suspect they may have some version of E10 in their 91 pump. I think there is an easy way to test at home, I'll have to look into it.
all our pumps are labeled e10 except ones specifically labeled zero for 91 fortunately. i also heard winter blends were going to be around a while longer than usual
 

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Discussion Starter #38
Tried to get a sample of gas out of the GTO and the daily and couldn't get a hose far enough down the filler tube to suck out a sample with my Mityvac.
 
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