New guy question - 2000' 1500 Silverado 5.3 2WD here... usually get around 13-15mpg around town. 18.5-19mpg on the hwy.(cruising @ 80mph) Best ever I set my cruise at 60 ...

2000' 1500 Silverado 5.3 2WD here... usually get around 13-15mpg around town. 18.5-19mpg on the hwy.(cruising @ 80mph)

Best ever I set my cruise at 60 mph on a cool rainy day and got 23 mpg on that tank. That was at sea level on flat ground with very few stops. Cruddy street tires and synthetics throughout drivetrain.

About to add Flex-a-light E-fan conversion kit to free up maybe 1-1.5mpg... but it's mostly to keep the A/C blasting cool in this horrible bumper to bumper traffic. The summer temps around here are extremely humid and well into the 100 deg range pretty often. That belt driven fan can only really move some good air when the engine is spinning faster... the e-fans move around 5,500cu/fpm even sitting at a red light if need be.

I just finished my very first tankful in the Sierra. I got 19.5 MPG. Now bear in mind, I was driving almost all highway, kept it between 60-65, and being very gentle (generally not getting much over 2,000 RPM) as I go through the break-in period. Regardless, I was really impressed! BTW, I have the 5.3L, and 3.42 gearing. I don't intend to drive it like that forever, and will slowly get more aggressive.
My Avalanche with the 5.3L and 4.10 gears got about 14-15.

I have a 01' 2500hd with the 6.0 and I get about the same and granted a I'm not a pedal pusher like in my younger days too

There are many things that affect mileage: tire inflation, type of tires, (wider etc), the type of fuel, weather, elevation, the speed at which you drive, the gear in which you drive, the speed with which you accelerate, engine maintenance, excessive idling, cruise control, the grade of motor oil you use, the condition of your air filter, the way you calculate the mpg.

Mileage is tough to predict.

Sounds like Hillary Clinton with the tire inflation!!! Ha! (Honestly, tire inflation affect less than 1% of your gas mileage, excluding running flats) But yes, the cumulative effect of all the little things can affect up to 10% or your gas mileage.

I have a 2008 1500 Ext Cab LT1 with a 4.10 ratio and 6.0L VortecMax, putting only premium in (91 octane here in CO, at 5280 feet) and I am getting 15-16 MPG so far. This is with both city and highway driving, and only goosing it when I need to.

nebot33 wrote:2007 1500 6.0 and I get 15.5 avg-tuned to 93 octane with the AFM turned off, and that includes trailering a boat.

Educate me, what does turning the AFM (Air Flow Meter?) do? How is stoichiometry achieved if the engine doesn't know the air coming in? How would changes in your driving elevation affect this?

Thanks!

Fyi

AFM = Active Fuel Management

Active Fuel Management (formerly known as Displacement on Demand) is a trademarked name for the automobile variable displacement technology from General Motors. It allows a V6 or V8 engine to "turn off" half of the cylinders under light-load conditions to improve fuel economy. Estimated performance on EPA tests show a 5.5%-7.5% improvement in fuel economy.

GM's current Active Fuel Management technology uses a solenoid to deactivate the lifters on selected cylinders of a pushrod V-layout engine.

Great, thanks for the AFM definition. AFM (air flow meter) and MAF (Mass air-flow sensor) are already programmed into my brain...now I have another acronym to learn!

I don't think my truck has AFM...how do I find out for sure? I've never felt it kick in before and haven't seen it on any of the material that came with the truck.

all 5.3 engine do, not all 6.0 engines do, I believe (not sure) that rpo L76 truck motor does have AFM.

If you still have the window sticker, it will say on there where is describes the engine.