30MPG LSx?

CincinnatiFiero · Post by **CincinnatiFiero** » Mon May 12, 2008 2:41 pm

I've heard rumblings on this site as well as others about 30mpg on the highway with 6speed F-bodies and GTO's. Is this true?

Something about re-tuning the rich 87 octane factory tunes to run 93 or something. And the natural bolt ons, intake, headers, and cat-back.

Is this true, that you can see 30mpg?

THE PUNISHER · Post by **THE PUNISHER** » Mon May 12, 2008 2:46 pm

My dad (mileage obsessed) recorded 29mpg on the highway in my moms 03 Vette with the Auto. Highway trip , kingston to niagara falls , 5hr trip.calculated in US gallons. He averaged 70mph car is dead nuts stock

He got 27mpg in his 87 on the way to alberta

Honest Don · Post by **Honest Don** » Mon May 12, 2008 3:11 pm

before I swapped cams, my 2000 Firebird would get as high as 32 on the highway, if I behaved myself. Even with the big cam, I still get in the high 20's

Kohburn · Post by **Kohburn** » Mon May 12, 2008 3:38 pm

a v8 can get good milage because it has enough toque to idle down the highway if it has tall enough gears..

no FWD tranny has the right gearing for those engines.

THE PUNISHER · Post by **THE PUNISHER** » Mon May 12, 2008 3:42 pm

Kohburn wrote:a v8 can get good milage because it has enough toque to idle down the highway if it has tall enough gears..

no FWD tranny has the right gearing for those engines.

The ones V8Archie uses have proper gearing.

Aaron · Post by **Aaron** » Mon May 12, 2008 4:16 pm

I got 34mpg on my drive to OK in the 2002 Camaro 6-speed, premium fuel, cruise control at the speed limit the entire trip.

On the way back to Colorado that fell to 28mpg. Something about climbing 6,000ft :scratch:

Still, averages to 31, not half bad. The aerodynamics, extremely tall 6th gear, and plenty of power without ever needing 5th all play a part.

CincinnatiFiero · Post by **CincinnatiFiero** » Tue May 13, 2008 2:40 pm

So the answer is yes, sweet. I assume a leaner fuel tune for premium fuel (providing its true the factory tune is pig rich so 87 will run in them), intake, header, and exhaust would also help?

Aaron · Post by **Aaron** » Tue May 13, 2008 2:52 pm

CincinnatiFiero wrote:So the answer is yes, sweet. I assume a leaner fuel tune for premium fuel (providing its true the factory tune is pig rich so 87 will run in them), intake, header, and exhaust would also help?

The headers and exhaust will help your economy, but not the intake. Not to mention the SLP lid is as good as any aftermarket one anyways. If you don't have a SLP lid, then get an aftermarket one. But if you do, there's no point.

Also, the tune isn't pig rich on premium, it's damn near perfect. If you run 87 it will run fine, except will start knocking at higher RPM/throttle positions. But the PCM will pull timing pretty quickly in that event, and will switch to maps with retarded timing curves.

Unsafe At Any Speed · Post by **Unsafe At Any Speed** » Tue May 13, 2008 3:14 pm

The most I've ever got in my V was like 20 mpg. But part of that was through the LA, so I wasn't in 6th the whole time.

Aaron · Post by **Aaron** » Tue May 13, 2008 3:19 pm

Unsafe At Any Speed wrote:The most I've ever got in my V was like 20 mpg. But part of that was through the LA, so I wasn't in 6th the whole time.

The V also is a little different. First, it is a 405hp variant, so the cam and heads are a bit more aggressive. Next, it weighs a lot more than the Camaro. Still, 20 is pretty low.

The Dark Side of Will · Tue May 13, 2008 4:04 pm

CTS-V: 3900#
GTO: 3600#
F-body: 3400#
Vette: 3200#

Expect gas mileage to drop as curb weight goes up.

Unsafe At Any Speed · Post by **Unsafe At Any Speed** » Tue May 13, 2008 4:28 pm

I understand all that. I know that my mpg is lower than other LSx vehicles. I just thought I would throw that in. I still think that is decent considering there were a few 4th gear pulls to manage traffic as well as a 'decent' pace the whole way. I am curious to see what I would get on an actual highway trip (no CA freeways). Supposedly one guy on the V forums got 27 mpg.

S8n · Post by **S8n** » Tue May 13, 2008 8:31 pm

In my '02 Z28, I could get high 20s, sometimes 30 just cruising around 70 mph. In my '06 GTO with long tubes, high flow cats, cat back, tune and CAI, I can only squeeze out 24 mpg. Around the same before it was modded.

The Dark Side of Will · Tue May 13, 2008 9:27 pm

I rented a brand new CTS a couple of days last week.

Admittedly I drove it like a rental...

The 3.6 V6 returned 21 mpg with the 6 speed automatic. I can't imagine how much fuel the V8 version of that car is going to flush.

Aaron · Post by **Aaron** » Tue May 13, 2008 9:49 pm

The brand new CTS? 300hp in the new body style? That car brings sex to an entire new level. It is drop dead gorgeous. I can't think of another sedan in its class that I'd even test drive to compare. The CTS could have a Fiero interior and I'd still buy it. I can't wait to see the V, though I'm not sure how GM could make this car look any more badass.

Unsafe At Any Speed · Post by **Unsafe At Any Speed** » Tue May 13, 2008 9:52 pm

I think the '09 V is only supposed to get like 14 city. I would deal with it though. That car is badass. It makes mine look like a 4 door Civic.

Aaron · Post by **Aaron** » Tue May 13, 2008 10:13 pm

With a 6.2l supercharged LSX pushing 550hp, I too would deal with it :thumbleft:

The Dark Side of Will · Tue May 13, 2008 10:46 pm

It's SOOO HEAVY, though. It does a good job of hiding its weight (even slides nicely), but the next day I spent about 7 hours (through LA traffic no less) in a 4 cyl/auto G6 that felt more nimble just because it was lighter. If the G6 had the CTS's level of suspension development, it would kill, despite being WWD.

crzyone · Post by **crzyone** » Tue May 13, 2008 11:40 pm

Aaron wrote:I can't wait to see the V, though I'm not sure how GM could make this car look any more badass.

By making it a 2 door :thumbleft:

My CTS gets about 25-28mpg cruising at 70-75mph. I don't have the advantage of direct injection like the new CTS either.

Aaron · Post by **Aaron** » Wed May 14, 2008 12:17 am

The 2 door looks sexy, up until the back end. Past the doors, it's ugly as fuck. It looks too tall.