V6 gas mileage

[Spicoli]

Originally Posted by TooCool5

Always re set the ECU after a mod or sensor change.
I did and get 30 - 33 avg on my highway trips to the Beach.
I expect it to drop soon as Oct 1st in New England they start dishing out the Winter gas formula.

Now that you posted that, it makes perfect sense. Going too fast and totally forgot about it. I think we've been in the winter formula in Michigan for a few weeks now. Thanks.

[JoshBobGuptaMarley]

18.4 avg.

[efpardo]

Originally Posted by Spicoli

OK, well over 600 posts to this thread and a quick review didn't find anything that explained my situation (sorry, I didn't look post by post).

My story.
2010 1LT A6.

Took a 1000 mile trip in Feb on mostly interstate toll roads. Average speed of about 67-68mph. Got 30.8 mpg on the DIC. Manual calculating was about the same. I am happy. Mileage was about 10,000 at that time. Combined city/highway, back and forth to work (10 miles each way), I was averaging 20 mpg. Still happy.

A couple of months ago, I installed a Roto-Fab cai and a DynoMax VT axle back exhaust. Been driving back and forth to work and getting about the same, maybe about 1mpg less. It sounds awesome, especially at full throttle, high RPM. I haven't had a chance to take any long trips, so I just assumed I would get the 30+ or higher mpg.

We left Saturday morning for the in-laws. 125 miles each way. Fresh fill up on the way out of town. Got on the highway, reset the DIC and drove 100miles at exactly 70mph. I had made this same trip before my mods, at 70 mph and gotten 29mpg pretty consistently. Saturday, I was at 23.5 mpg. I was like, WTF? No heavy acceleration, no stop and go driving, just a steady 70mph for those 100 miles. Towards the end of the trip, about the last 25 miles or so, the speed limit is 55 mph. Reset the DIC again and drove exactly 55 mph. Mileage increased to 28.5 mph when I am used to getting 31 on that stretch (before mods).

So I'm sitting up at my in-laws stewing over what is happening. The car seems to have developed a small stumble from time to time. I couldn't pin point anything specific so I just figured it was my imagination. Got to thinking maybe I picked up some bad fuel. My mods couldn't be causing this could they? Hadn't read anything about it here, so I don't think so. I begin to wonder about the ECU maybe picking up some bad habits (probably from my bad driving habits, hehe), and had adjusted the A/F ratio, timing, cam timing, something. So I decided to try to reset it. Disconnected the battery for 30 minutes and reconnected. Took off this morning for the drive back home. Same route, same weather, same everything. Drove the 55mph for the first 25 miles and got about 32mpg on the DIC. Hit the 70mph zone and reset the DIC again, drove the 100 and ended up at 30.5 mpg. A 7mpg gain by disconnecting the battery for 30 minutes. I guess it really shouldn't be called a gain, but more of a recovery. OK, I recovered 7mpg. Spicoli is happy again.

OK gals and guys, anyone ever heard of anything like this?

Thanks in advance for the feedback.

I think a #20 fuse pull may have helped too.

[Spiker]

Ok so I just bought a brand new 2015 2LT RS 6SPD and well my first tank was bad like 15 and I didn't think much well over time I've been driving just hit 3k miles last night and my mileage is horrible like my DIC shows 14.4 and manual math shows anywhere from 13.8 to 14.5 and I am putting mid grade 89 no ethonal in it I don't drive very aggressive other then the normal pass here and their and I am pretty much driving through the country very little city as we only have stop signs every mile and stoplight no really any traffic and one care to help with with this problem or know why and it's completely stock I haven't done anything yet and I only get around 240-250 miles per tank and that's pushing it filling it up with 17 gallons so anyone wanna help thanks!!

[BSR-1]

Originally Posted by Spiker

Ok so I just bought a brand new 2015 2LT RS 6SPD and well my first tank was bad like 15 and I didn't think much well over time I've been driving just hit 3k miles last night and my mileage is horrible like my DIC shows 14.4 and manual math shows anywhere from 13.8 to 14.5 and I am putting mid grade 89 no ethonal in it I don't drive very aggressive other then the normal pass here and their and I am pretty much driving through the country very little city as we only have stop signs every mile and stoplight no really any traffic and one care to help with with this problem or know why and it's completely stock I haven't done anything yet and I only get around 240-250 miles per tank and that's pushing it filling it up with 17 gallons so anyone wanna help thanks!!

I drive like a complete idiot and I get 20.6. I hit 97 MPH at one point on the freeway today (I'm always doing 80+).
I do have a CAI and mufflers, otherwise completely stock. 33,xxx miles.
I use the cheap gas. Unless you have a built motor I wouldn't suggest running higher octane.

[wvyankee2]

I'm running 89octane and ride about 80% interstate at 80MPH. Getting 23.5mpg consistently with Automatic.

[William.23]

Apparently I'm running at 17.4 MPH Automatic -

BUt I haven't reset the miles at all from 3 miles(I got my car) till now 32200. Probably when I first got my car i was driving it all sporadically :P now kind of calm (:

[Tmick5jr]

Originally Posted by BSR-1

I drive like a complete idiot and I get 20.6. I hit 97 MPH at one point on the freeway today (I'm always doing 80+).
I do have a CAI and mufflers, otherwise completely stock. 33,xxx miles.
I use the cheap gas. Unless you have a built motor I wouldn't suggest running higher octane.

yea, you don't want that high quality fuel to destroy your motor..

[BSR-1]

Originally Posted by Tmick5jr

yea, you don't want that high quality fuel to destroy your motor..

And you're a fuel expert?
Higher octane is just more knock resistant. If you're not running high compression it's a waste. Fail?

[Mr. Stacy]

Originally Posted by BSR-1

And you're a fuel expert?
Higher octane is just more knock resistant. If you're not running high compression it's a waste. Fail?

Exactly. Octane is a measure of compression ability. Only high compression engines see ANY benefit of anything over 87. ALL grades have high quality detergents.

Long, hot (90+) trips or a *really* heavy load. Other than that >87 is a waste.

[JantzenOKC]

LFX's are high compression motors (11.5:1) and they like 91 octane. They run fine on 87 but timing IS being pulled, you can watch the KR with any cheap scantool. I used to feel it most at part throttle acceleration. Makes more power with 91 than 87, no doubt.

[Mr. Stacy]

Originally Posted by JantzenOKC

LFX's are high compression motors (11.5:1) and they like 91 octane. They run fine on 87 but timing IS being pulled, you can watch the KR with any cheap scantool. I used to feel it most at part throttle acceleration. Makes more power with 91 than 87, no doubt.

Maybe for a turbo.

You can't get more power from more octane. You can compress higher octane fuel more before it ignites by itself. That is all.

If your engine is designed to highly compress the fuel (as in a turbo or other such high performance performance feature) then you actually NEED a higher octane rating.

Octane rating is a measure of it's ability to compress before spontaneous combustion. If your engine (LFX) does not compress the fuel enough to cause spontaneous combustion, the money you spend on a higher octane rating is wasted.

GM 3.6L V6 LFX Engine Specs
Type: 3.6L V6
Displacement: 3564 cc (217 ci)
Engine Orientation: Longitudinal and Transverse
Compression ratio: 11.5:1
Valve configuration: Dual overhead camshafts
Valves per cylinder: 4
Assembly site/s: St. Catharines, ON; Flint, MI; Melbourne, Australia; Ramos Arizpe, Mexico
Valve lifters: Roller follower with hydraulic lash adjusters
Firing order: 1-2-3-4-5-6
Bore x stroke: 94.0 x 85.6 mm
Bore Center (mm): 103
Bore Area (cm2) (total engine bore area): 416.37
Fuel system: Direct Injection
Fuel Type: Regular Unleaded, E85 capable

http://www.nicoclub.com/archives/gas...ane-myths.html


Read more: http://gmauthority.com/blog/gm/gm-en...#ixzz41a28ujoA

[JantzenOKC]

Originally Posted by Mr. Stacy

Maybe for a turbo.

You can't get more power from more octane. You can compress higher octane fuel more before it ignites by itself. That is all.

If your engine is designed to highly compress the fuel (as in a turbo or other such high performance performance feature) then you actually NEED a higher octane rating.

Octane rating is a measure of it's ability to compress before spontaneous combustion. If your engine (LFX) does not compress the fuel enough to cause spontaneous combustion, the money you spend on a higher octane rating is wasted.

GM 3.6L V6 LFX Engine Specs
Type: 3.6L V6
Displacement: 3564 cc (217 ci)
Engine Orientation: Longitudinal and Transverse
Compression ratio: 11.5:1
Valve configuration: Dual overhead camshafts
Valves per cylinder: 4
Assembly site/s: St. Catharines, ON; Flint, MI; Melbourne, Australia; Ramos Arizpe, Mexico
Valve lifters: Roller follower with hydraulic lash adjusters
Firing order: 1-2-3-4-5-6
Bore x stroke: 94.0 x 85.6 mm
Bore Center (mm): 103
Bore Area (cm2) (total engine bore area): 416.37
Fuel system: Direct Injection
Fuel Type: Regular Unleaded, E85 capable

http://www.nicoclub.com/archives/gas...ane-myths.html


Read more: http://gmauthority.com/blog/gm/gm-en...#ixzz41a28ujoA

I'm talking about the LFX in stock form. I've never ran less than 93 since being boosted, as I'm tuned for 93.

A stock LFX runs fine on 87, but it pulls timing (knock reduction) to be able to do it. If you run 91 it will pull a lot less timing if any at all. Less timing = less power, more timing = more power. So yes 91 will make more power in our cars than 87 will. But not because "91 makes more power" but because 91 allows the ecm to run the timing it was designed to run. It just has the ability to instantly reduce the timing as soon as knock is detected. That way the masses can fill up with 87 and be happy.

[Mr. Stacy]

Originally Posted by JantzenOKC

I'm talking about the LFX in stock form. I've never ran less than 93 since being boosted, as I'm tuned for 93.

A stock LFX runs fine on 87, but it pulls timing (knock reduction) to be able to do it. If you run 91 it will pull a lot less timing if any at all. Less timing = less power, more timing = more power. So yes 91 will make more power in our cars than 87 will. But not because "91 makes more power" but because 91 allows the ecm to run the timing it was designed to run. It just has the ability to instantly reduce the timing as soon as knock is detected. That way the masses can fill up with 87 and be happy.

So a stock LFX will tune itself to 91?