Vortec 350 - 454 fuel economy
 

I'm just curious if anyone has fuel economy figure for the vortec 350's and 454's in a k2500 style truck. Is there much difference?

Around 5-8 mpg depending on your gearing. Personally I'd prefer the 454 is you do much hauling. The only reason being in that with it being a 3/4 ton, the 454 and its bigger torque curve, it doesn't have to work as hard. The downside is that you trade off fuel economy.

I have had them both and I decided to stay with the big block for pulling. My trucks compared like this -

99 2500 P.U. w/ 5.7 - empty 16 MPG, towing loaded 16' enclosed trailer - 11 MPG

96 2500 Suburban w/ 454 - empty 14.5 MPG, towing same 16' trailer - 12-13 MPG, and 11 MPG pulling our pontoon boat through the mountains (it's a freakin parachute back there)

I also had a 96 3500 dually that got the same mileage as the Suburban - I actually got 14.7 coming from Florida to SC unloaded.

As you can see there isn't much difference and the big block actually gets better towing. The huge difference is the power. The 454 seriously out pulls the 350 so to me it's a no brainer.

Too bad they stop making the big block!

WOW! I have a 95 HD3500 pickup with a lightly loaded utility bed and I am only getting 7 MPG. I better check things out. The truck is new to me.

You have a couple things against you - the 3500HD is a very heavy and you have a TBI motor. You might be able to squeeze a little more out of it, but not much.

I have a 1998 K2500, with the 5.7, and I get 14 MPG with no load.

I have a 1995 1500 extended cab 4wd 5.7L auto, and I get 23MPG with no load and I am having over fueling issues! Granted our galon in Canada is different to the USA.

Question for Shamrock
 

I have a 2000 3/4t crewcab 454 vortec, stock tire size, auto transmission and 373 gears and normally get between 11-12mpg running empty. To date I have installed a K&N cold air intake, true dual exhausts and JBA shorty headers to try and increase the fuel economy with little or no results. I have also purchased the hypertech econ progammer and it had very little effect on the fuel economy. I would be interested in any suhhestions you or memebers of the forum might have. Also there is a shop in South Dakota that does custom tunes on trucks and I was wondering if anyone has had any favorable results from this type of tune.

thanks jaeger

I was basing my previous opinions on a 99 2500 with a 5.7 Vortec that I used to have. I then went to a 98 with a 454. They got real similar mileage and of course the big block had more power. I recently picked up a 98 2500 with a 5.7 and it is getting decent mileage. The motor is fresh so that is helping I am sure. I drove down to Atlanta empty and got 16 MPG. I hooked to a car trailer with another trailer on top and came back at 14-15 MPG. It doesn't have quite the power as the 454, but for what I haul it does fine. The 2 trailers on top of each other were hardly noticed back there at all. It was probably only a 3000 pound load so it shouldn't have been noticed.

I've got a '90 Suburban, 454, 3.73 gears and tow a 26 ft travel trailer (probably about 7,500 lbs). Even installed a GearVendor overdrive.

Pretty much use it only for towing now days, and get about 9 miles/gallon. Solo get about 13 mpg. Everything except the transmission overdrive and Aluminum radiator is stock.

Hey Stevie, how is the GV overdrive working out? I have been looking at those. What is your RPM at 60 mph with the overdrive on. Is the overdrive automatic or do you switch it on. Thanks

Gregory,

Honestly, for me it’s been great. But there are several factors that you must consider before you buy: Cost, age of vehicle, cost, your type of driving, how many speeds the vehicle already has, cost, and what type of vehicle you have. Oh, and cost.
I don’t know what the highway speed RPM is. But it definitely lowers it, and makes the vehicle a little quieter.
Let me explain a few other things. This is not your everyday add-on, it is expensive. I would only suggest it for a vehicle that doesn’t have an existing over-drive. My Suburban only had the 3-speed automatic. I’ll repeat that, if you have an overdrive, don’t buy this product. Give your money to a worthy charity instead. Because having it installed can also create other problems (additional maintenance to worry about, and a possible drive-train issue I’ll discuss later).
Does it get me up a hill faster? Maybe 1 out of 10 hills I may find a “split” gear to be better than the stock gears. Faster? No. But I do like the overdrive feature, as it lowers rpm and noise. And I am a mechanical engineer, and enjoy being able to control an automatic transmission a little more. Does it go into overdrive automatically? Yes. You can also do it manually with a foot switch…very cool. But is it worth $2700 for having a cool switch on the floor? Only if you have a 3 speed transmission.
Cons.. and these are important. My Suburban came with a two-piece drive shaft, and when the GV was installed they replaced it with a one piece drive shaft that is pretty long. I now get a nasty vibration at speeds above 70mph, which is because the shaft is hitting a natural frequency (“critical speed”). It bugs me, but not much I can do about it, nor do I want to bother. As I only use the truck to tow a trailer, so rarely am I over 65mph anyway. I still have the original shafts, but the center bearing would need to be moved aft about a foot to balance everything out. Not worth it to me. Also, one more thing to maintain, although relatively easy. Downshifting takes a bit of practice as you need to press on the accelerator to rev-up the engine a bit (if you don’t you will feel a heck of a jolt). Final “con”… I think the cost is too much.
Pros.. It is cool, and a little fun. And it does work flawlessly. I’ve had mine for about 10 years, maybe 70,000 miles, and it still works great.
Any other questions?
Steve

Ya know Stevie, your post makes me really glad that I have a stock overdrive tranny ;)

Gents... my dream truck is a Duramax with the 6 speed tranny. ...Someday.