Best Cruise Speed

flyboyron · August 6, 2014

I have an 09 Silverado Ext Cab with a 5.3L and the 4 speed trans. I also have the 3.73 rear end.

At 70mph I am reading 2000 rpms.

What speed does the engine run best (rpm wise), and what is a good cruise speed to set the cruise control at. With the EFI engine, does it make a difference on your truck in performance at any different speeds you drive? Say 65mph verses 75mph?

I remember many moons ago, when you got over a certain speed, you would have more power but then those other 2 barrels would open up and your mileage would drop quite a bit.

white1500 · August 6, 2014

Is this your first truck without carbs??? You might want to read up on how efi and now dfi engines work.

The lower the rpms the less fuel your're using, and with lower speed comes less drag (air resistance).

Having said that I like to cruise at up to 75mph but that's with perfect straight roads.

TooTall1 · August 6, 2014

Basically it comes down to the faster you try to push a brick through the air, the more fuel you burn. I've found I get my best mileage at 55-60, but on the interstate here I drive 65 which is the speed limit. Anything over that and you really start burning gas.

Snow White · August 6, 2014

Have the same truck... first piece of advice, don't use cruise if you're trying to get fuel mileage. With our trucks, the 4cylinder mode is key and keeping it in 4cyl mode. It's kinda like keeping the secondaries on the carb closed lol... by keeping the other 4cylinders off.

Don't use cruise, leverage hills for a running start and drive it like a tractor trailer and you'll do well.

There is no speed or rpm that is more important than evaluating the terrain and resistance you are confronted with... if you have a tailwind go 75.... if you have a headwind go 65.... downhill let-er rip, up hill keep backing down the throttle

it is very similar to trying to keep the secondaries closed, or towing a huge trailer with an under powered 4 cylinder lol. If you do this, when you do waylay into, man, it sure seems like it's loaded with power.

Mike1220 · August 7, 2014

If you want better mileage and are not impatient to get where you are going, then go 60-65 mph. I can usually avg about 25-27 mpg at that speed. However, I grow impatient. So I drive at 70-80 mph. Avg between 22-19 mpg (at the respective speed)

Gurrzt · August 7, 2014

I like to keep the rpm's just under 2k (80mph).

MikeNH · August 7, 2014

Have the same truck... first piece of advice, don't use cruise if you're trying to get fuel mileage. With our trucks, the 4cylinder mode is key and keeping it in 4cyl mode. It's kinda like keeping the secondaries on the carb closed lol... by keeping the other 4cylinders off.

Don't use cruise, leverage hills for a running start and drive it like a tractor trailer and you'll do well.

There is no speed or rpm that is more important than evaluating the terrain and resistance you are confronted with... if you have a tailwind go 75.... if you have a headwind go 65.... downhill let-er rip, up hill keep backing down the throttle

it is very similar to trying to keep the secondaries closed, or towing a huge trailer with an under powered 4 cylinder lol. If you do this, when you do waylay into, man, it sure seems like it's loaded with power.

Hardly. AFM (4 cyl mode) doesn't do much at all on the 900-series trucks. Most who disable it report at most a 1 MPG loss. It's just fluff to help with the EPA test procedure. No real world benefits.

2017SierraSLT · August 7, 2014

No change in mileage for me with either the level or the AFM disable.

Snow White · August 7, 2014

Hardly. AFM (4 cyl mode) doesn't do much at all on the 900-series trucks. Most who disable it report at most a 1 MPG loss. It's just fluff to help with the EPA test procedure. No real world benefits.

Maybe that is your experience, but it is not mine, so my advice is based on my 93,000 miles of experience.

Snow White · August 7, 2014

No change in mileage for me with either the level or the AFM disable.

Is your truck a 2013 with the 6spd or an older 4spd? Over 93,000 miles I've averaged 17.6mpg.

MikeNH · August 7, 2014

Probably about the same I get and I have a V8 all the time. If you don't believe me you can search, dozens of members have reported the same result. AFM is just a gimmick to get a bit more in the EPA test, nothing more.