04 Tahoe 20mpg goal

[darcane]

Originally Posted by cosmick

The 3.23s are too tall for best mpg, but they do let you shift to a lower gear at higher speeds, which can help highway towing.
When it was new, and came with 3.42s standard, GM called the 4.8 " a real sweetheart " in regard to fuel efficiency, ( stock ).

Per the owner's manual, for my Tahoe (2005) 3.42 gears aren't actually offered. They were standard on 4wd and 2wd 5.3L Suburbans could get it, but 2WD Tahoes only got 3.23 or 3.73. Mine is RPO code GU5, so I have the 3.23s

I've had tank averages in our Tahoe at 23-25mpg... but only on long highway trips. This is just setting the cruise control and letting it go down the freeway.

On my old Silverado, I had a handful of tank averages at 20-22mpg, commuting in mixed traffic. I could have done so more often, but I rarely went a whole tank w/o heavy loads/towing, especially considering a tank could get me nearly 700miles.

Again, for belly pan ideas, check the Silverado thread in my signature. I have a few pictures in there of how I built the framework it mounts to. Coroplast worked well and even had some hard impacts with road debris and was left mostly unscathed. It's pretty durable, but inexpensive and lightweight.

[cosmick]

When the 4.8 was new, was 99, not 05, sorry for not clarifying.

[Andrewhans]

Just achieved my current one way personal best from work to home.

50mph max, load based cruising, mirrors folded in, engine deceleration whenever possible neutral coasting up to stop lights as well, AC off, windows up, 93oct, 100% full tank of fuel.

So next on list is putting the grill block back on. 50% to start then I'll go either 100% or 75%.

After that it'll be the belly pan and then the rest of the bottom.

I like what you did for your belly pan. Looks simple and I could carry that idea almost all the way to the rear of Tahoe.

[Andrewhans]

Double post

[Andrewhans]

Put the 50% grill block on today.

I must be doing the pulse and glide thing wrong. My mileage went down to 17.3 on the same trip as that personal best pulsing to 60 and slowing down to 45. It was the sweetspot for the lockup converter and deceleration fuel cutoff on my engine.

During the pulse I was accelerating briskly, maybe too fast though. I'll keep trying. It seems thats how a lot of people get a boost to their numbers.

[Frank Lee]

You aren't getting any "glide" with DFCO; you are getting engine braking. P&G basically isn't going to go well with an automatic.

[Andrewhans]

Fair enough. I'll switch back to how I was driving before. I can only really get around 30% load with the auto before it kicks BACK down to a lower gear during acceleration.

Is that enough load to benefit from the quick acceleration and better bsfc?

[Frank Lee]

In my opinion that is better than kicking down a gear no matter what the load.

I don't have any instrumentation. But being familiar with my a/t vehicles, I know the minimum speeds I can "tease" the upshifts and torque converter lockup at by slightly lifting the gas pedal. Top gear all the way, baby.

[Andrewhans]

Seeing as I have a bigger engine than most, does anybody have any suggestions of when I should be shifting?
2000, 2500 more?

I have been doing around a 2200 shift point while accelerating with high load and letting off to get the trans to shift early and then I roll back into the throttle. It has been what "feels" like I'm acceleraring quickly but not wasting energy. How accurate that feeling is, I don't know.

[JRMichler]

Originally Posted by Andrewhans

I have been doing around a 2200 shift point while accelerating with high load and letting off to get the trans to shift early and then I roll back into the throttle. It has been what "feels" like I'm acceleraring quickly but not wasting energy. How accurate that feeling is, I don't know.

That feeling is probably more accurate than you think. Especially since your acceleration technique sounds spot on.

There is a range of acceleration rates that all give close to the same gas mileage. If you accelerate in that range and move with traffic, you are doing about as well as can be expected.