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LS4 vs 3800 blower mpg


KnightOwl
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I'm curious how many here have the LS4 and what kind of real world mpg do you get. Do you have DoD disabled? And for those with M90 3800s, especially if you've done mods for the power, how much has your mpg suffered if at all?

 

Just curious....

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I have one of each and my LS4 get's better gas mileage on the highway. I get like 25 on the highway with the GXP on premium gasoline and like 20 with E85. I have an overkill tune and an ethanol content sensor so I can run the E85.

 

my 2001 GTP runs E85 only and it get's about 18 on the highway. this car is not my daily and has an xp cam, ported heads, gen 5, headers and methanol injection

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With a mostly stock L67, I would average 26-28 MPG on the highway. I "hypermiled" my old GTP out to Toledo once and I averaged over 32.

 

My Regal runs E85 so it's much worse obviously.

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I've always been more intrigued by "Miles per Dollar" Even before I had an L67 I ran 93 octane because it was literally cheaper to run when I did the math. The Regal (then L36) and my truck both got better economy with 93.

 

A lot has changed in fuel pricing since then but it was .30 / gallon more at a time when gas was at nearly $4.00/gallon.

 

Way back when gas was $1/gallon the additional .20 or .30 cents was significant enough that 87 was cheaper.

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My LQ1 was like that, too, and got it's best mileage with 93.  Interestingly enough, the L98 in the IROC gets it's best mileage with 93 octane, but the few times I've spent extra for 100% gas (no ethanol), I didn't see any change at all. 

 

I actually get about the same mileage with the IROC as I did my LQ1 Cutlass--which I would never have expected.  Both average between 20-21.5 on my daily commute.

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All of our fuels in this part of VA are 10% ethanol, and its funny how my EcoBoost Escape calls for at least 91, but I've run 89 and 93 and cant tell the difference. I thought maybe the 93 would deliver better mileage but it hasn't. I've also been told winter blend fuels don't deliver great mpg numbers anyway.

 

 

If I got a LS4, I'd definitely disable DoD, because my Magnum had a similar system on the Hemi and the exhaust note in 4cyl mode was horrible. That car averaged 16-18 combined and about 22-23hwy. I would be plenty happy with those numbers out of an LS4 (or a stout 3800 for that matter.)

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Getting rid of my 35PSI Coopers and putting the 47PSI Yokos on made something like a 2 MPG difference. And it handled so much better too with less sidewall roll and a wider section width.

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I usually average 22 day to day, right now though im below 20 be that my driving or winter fuels. Ive done daytrips and gotten around 24 cruising 75 with all the windows half down

 

Sent from my SM-N900T using Tapatalk

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With 3.69's my GXP was getting about 21-22 highway at 70~ on pump 92+.  Granted it was turning a lot more at cruise than an OEM gear.

 

Ethanol killed that, lol.  I think it was averaging about 15~ or so at that point.

 

My built motor/heads/cam GTP with 3.29's was pulling 30's on the highway; pump gas. 

 

Both street tuned; no dyno business.  Only tossed the GXP on the dyno to grab numbers.

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