Best Engine For Economy vs. Grunt

[FoolSizeK5]

Fuelinjection

Go with a multiport fuel injection and and a 700 with a doubler will get you best economy you can get with a motor that will have good power but won't have enough tourque to kill a built 700 and a doubler so you don't have to go grazy low with the gears could get you 14 or better i'm hopping to get 17 on the high way with my New Votec 350 when it's running i hope next week. I'll let you know. But that won't last long after lift,tires, and gears. Want real economy?? build the truck and take a honda to work.

 

[beater_k20]

we killed this thread nearly a month ago. thanks for playing though.

 

[Blue85]

or why not just put a crate motor in it that has about the same hp/tq? fuel economy wont be that much different, and it likely wouldnt require premium, and would be much cheaper and easier.

OK, I know this thread is old. The fuel economy of the super3.8 will be much better than a crate V8, better even than the 4.3. These engines offer true V6 economy with V8 power. Varying the volumetric efficiency is almost like varying the displacement.

But I agree with what others have posted. You should only spend so much to get more fuel economy. To spend $2000 on an engine to bring you from 12MPG to 15MPG requires you to drive over 50,000 miles just to recover your cost.

 

[gmc4cw]

383 stroker.

 

[beastofablaze]

Pretty sure he was right on this one

TPI isn't tough to install, but unless you buy an entire running car for less than a grand, expect to be putting at least a grand into it to get it running.

TBI isn't as high of performance, but it does well for a truck, and is boat loads cheaper. (300 - 400 for a complete setup)

I put TPI into my K25, I'm sitting at approx 1000 USD into it, and looking at least 150 - 200 bucks more till it runs.

Give holley a call they, can setup you up with a tbi system ready to support 350 plus hp for around 7-800 bucks with all brand new stuff and another 150 or so to get the computer happy...... if you want to save some dough try a cfm tech tbi instead of the holley throttle body..... that will save you about 150 bucks. Some guys on thirdgen are claiming 400 hp with holley tbi setups.... however you need to know your way around a computer and have a VERY good understanding on how your rigs computer works and controls the engine to get the right fuel mixture and not kill it by running lean.

 

[yellowK20]

Blown 540" Merlin, not real good mileage but the fun factor is worth it!

sorry to hijack but you should post some pics of your rig sounds awesome

 

[blackblazer717]

wow im surpriseds the "Built 350" and Turboed dizzle" are pritty much neck and neck.
i was never a fan on the fuel economy of a stock 6.2 let alone one thats turboed
if you go that route will you get a kit? or frankin turbo your own?

LUKE

 

[chris walker]

why dont you keep the 350 and strip every thing but the drivers seat(one of those plastic racing seats) and radio out of the k5 just taking all that crap out will get you atleast 2 mpg more may be more but I'm talking everything carpet seats but the driver the dash board door panels and lights all non inportant electrical equipment then the bumpers a/c heater and the top then buy some really light wheels and tires

 

[rjfguitar]

How about you go and buy a truck first, then worry about engine modifications and/or swaps.

 

[Russell]

Woo! Old post!

Still say diesel!

 

[jdemaris]

You can definitely get over 20 mpg with a 6.2 on highway, esspecially if you turbocharge it. But, remember, those engines are not to be compared to a gasoline engine, which is a common mistake that is made.

A stock K5 Blazer with a stock 6.2 -and stock tires, if geared right - will get up to 23 MPG on the highway. A stock 1/2 4WD pickup with 6.2 and overdrive about the same. Oversize tires or very high altitudes will bring the mileage down a bit.
Adding a turbocharger though, usually will result in worse mileage overall, not better. That mostly because the fuel delivery is turned up and hills are climbed faster. I've got close to 40 trucks with 6.2s in many different variations and usually have four on the road at any given time (I switch back and forth).
All my K5 6.2 diesel Blazers with 700R4 trans., 3.08 axles and stock tires get 16 MPG around town and 21-23 MPG on the highway at 65 MPH.

All my K5 6.2 diesel Blazers with TH400 trans., 3.08 axles and stock tires get 16 MPG around town and 20 MPG on the highway.

All my K20 or V20 3/4 4WD Suburbans with 6.2 diesel, TH400 trans. (no overdrive), 3.73 axles, and stock 16" tires get 13 MPG around town and a high of 19 MPG on the highway.

My 1991 V10 1/2 4WD Suburban with 6.2 diesel, 700R4 trans, and 3.42 axles gets 14 MPG around town and up to 21 MPG on the highway.

My 1982 K10 1/2 ton 4WD pickup with 6.2 diesel, four speed overdrive manual trans. (NP833), and 3.08 axles gets 17 MPG around town and has gotten 24 MPH on the highway.

6.2 tops out at like 3500 rpm, while a 350 tops out at like 5500. Diesels are designed to make good torque, and go on long hauls, not random trips around town. They like to be run long and hard, not stop and go

I'd say the 6.2 really tops out at around 2700 RPM. Even though it's governed to 3600 RPM, there not much of a power gain past 2700 RPM - just more noise and worse fuel mileage. That's why gearing is so important. It's peak RPM range for torque and fuel efficiency is around 1800-2000 RPM.
But - about how diesels like to be run hard - I don't think it applies to the 6.2. With heavy duty diesel engines - yes it does apply to a degree. The 6.2 is a light-duty diesel. It is NOT meant to be lugged, not meant to do hard pulling. It does need to reach operating temperature to run it best - but so do gas engines. It also takes a lot more to start a diesel with 21.5 to 1 compression, so lots of starting and stopping is hard on batteries, glow plugs, and starter motors.

In answer to another question about 700R4s in 6.2s - many if not most came that way from 1982 to past 1990 if in 1/2 ton version with the C-code 6.2 diesel. 700R4 is the only automatic GM used in the Blazer diesels for civilian use. Military versions came with TH400s. Most 1/2 trucks, vans, and Suburbans also usually came with 700R4s. 3/4 ton vehicles - along with slightly more powerful J-code 6.2 diesels often came with TH400s for heavy towing. With standard transmssions - in 1/2 tons, often the four-speed manual overdrive trans was used - NP833. Also the heavy non-OD four-speed Muncie.

 

[rjfguitar]

A stock K5 Blazer with a stock 6.2 -and stock tires, if geared right - will get up to 23 MPG on the highway. A stock 1/2 4WD pickup with 6.2 and overdrive about the same. Oversize tires or very high altitudes will bring the mileage down a bit.
Adding a turbocharger though, usually will result in worse mileage overall, not better. That mostly because the fuel delivery is turned up and hills are climbed faster.

I'm going to say I have to disagree with you that a turbo'd 6.2 will get worse mileage. Now I say that with respect and ready to eat crow, as it sounds like you know your stuff with 6.2s.

But, with that, It seems I remember people mentioning a mileage increase after turboing their 6.2 and just because you can climb the hill faster doesn't mean you get worse mileage. The faster you get to the top, the sooner you get out of the throttle. There is obviously a variable to that with how much fuel it would take to get to the top faster vs. limiting power but staying into it nearly twice as long. Generally, getting up the hill faster with a turbo'd motor gets better fuel mileage results in my experience, mainly due to still staying efficient with more fuel due to the turbo.

Another thing I would say is that most newer rigs get better mileage than a 6.2 in identical trucks, and obviously all late model stuff is higher powered turbo charged direct injected engines.

 

[MuddinManny]

If you're gonna build, build a....

383 Stroker!
​

 

[jdemaris]

I'm going to say I have to disagree with you that a turbo'd 6.2 will get worse mileage. Now I say that with respect and ready to eat crow, as it sounds like you know your stuff with 6.2s.

Another thing I would say is that most newer rigs get better mileage than a 6.2 in identical trucks, and obviously all late model stuff is higher powered turbo charged direct injected engines.

Not in my experience - and I've got several turbo diesels. In theory, a turbo can enhance effeciency - but it rarely happens. Turbo was original used as an "altitude compensator", not as a high-performance option. Take, for example the Banks turbo kit for the 6.2 diesel. Part of the installation is turning the fuel delivery up - because Banks wants customers to have big power gains. If you installed the turbo, but kept fuel delivery close to original, and drove the same speeds - it seems there would be a mileage gain. Do you know anyone that has ever spent the money on a turbo system and NOT turned the fuel up? I don't.
You mention newer turbo diesels being more fuel-efficient than the 6.2s. Not entirely true. Many later 6.5s with turbo were dogs and got worse fuel mileage. There were many changes in the engines besides just the turbo. When GM converted the 6.2 to the 6.5, and added the turbo, the precombustion chambers were changed, the angle of the injectors was changed, the opening pressure was changed, etc. etc. Even with the later Isuzu Duramax DI diesels - some got lousy mileage and some excellent. My neighbor has one and has never gotten better than 14 MPG on the highway - empty - since the day it was new. I've met others than have gotten 20+.
For myself - when I have to tow - I always use on of my turbo-diesels - usually my 94 Ford F250 with the IDI 7.3 turbo. By using it, instead of an NA 6.2, and pulling a 7000 lb. trailer, I climb steep hills as 55 MPH instead of 35 MPH but fuel mileage is worse, not better than with the 6.2. Now, if I purposely climbed the hills at 35 MPH ?? I don't know, never tried it - having more towing power is the reason I have the turbo 7.3. Even without the turbo, the older 6.9s and 7.3s are better built engines than the 6.2s and 6.5s. - in many ways.
By the way - just for comparison - I've got an 85 Ford F250 with a 6.9 diesel and no turbo - and no overdrive with 4.10 axles. My 94 Ford has the 7.3 turbo-diesel WITH overdrive. Yet, the turbo gets a little worse fuel mileage when driven empty - even with the overdrive.
Back to your comment about turbos, modern diesels, and better fuel mileage. It's NOT just the turbos. It other things, e.g. electronic fuel delivery monitoring, electronic engine balancing by fuel metering to individual cylinders, electronic timing adance, higher injection pressures - sometimes with common rail injection - and most importantly - DIRECT INJECTION - versus the older IDI like the 6.2s/6.5s uses. If done properly, DI is more fuel-efficient than IDI and puts less heat into the cooling system. Take the Cummins diesel that Dodge uses. Generally speaking, it is 30% more efficient than a 6.2 diesel - and NOT just because of the turbo.
On a different note - is anybody doing trail climbing actually driving the same rigs on the road? If not, why not use heating oil for fuel? I just bought 500 gallons and it cost $1.90 per gallon. Gas at the pump is $2.50 and diesel is $2.90. The off-road heating oil/diesel is actually better for the 6.2 diesel than pump fuel - but of course - not legal for public highway use. It has better lube for the injection pump. This makes me wonder why anyone would want to run SVO in any diesel with a rotary injection pump (like the 6.2, 6.5, 6.9 and 7.3 Ford, etc.). The rotary pump is the worst option out there for SVO use and tends to suffer wear problems with alternative fuels unless you are VERY careful.

 

[rjfguitar]

Well, everyone's experiences are different. I've heard different people here mention mileage went up with the Banks get up on their 6.2's. I got into it with a guy on towrig about 6.2's, and also mentioned he was getting better mileage, his 6.2 is turbo'd.

Who knows really. Every truck is different.

 

[OffRoad]

you can argue/discus till the world ends

DO THIS:

1. buy a civic

2. put whatever motor you want in your truck.

 

[muddybuddy]

the reason mpg might decrease with a turbo on a 6.2 is because u got more power + you want to enjoy it more = more throttle i think if driven the same, they will net the same mpg or slightly better for the turbo, because it will require less shifting to get up hills with less stress on the motor

 

[bear76]

I'm thinking a 250/465/205 combo for my next truck. So, I guess I vote nekkid.

 

[yoshisv]

Here's what you do: Hit the junkyards and grab both a Camaro 3.8L engine and a Pontiac/Buick/Olds Supercharged 3800 engine with the PCM and wiring. Swap all of the supercharged internals (it's all roller) into the Camaro block. Use the whole SC top end and controls. Now you have a S/C 3.8L V6 that bolts to your Chevy transmission and gives you like 300HP and 350TQ (with pulley, headers and PCM flash). It will take premium gas, but should give the kind of fuel economy you're looking for.

I've always wanted to try this.

I like this idea. My 01 grand prix gtp had the 3.8sc motor. 240hp, And 26.5mpg

 

[K5dreamer]

well i guess it all depends on your definition of performance, but im completely happy with my CUCV stock with the three speed TH400. I mean, ive got my camaro when i want to go fast, but the truck will get up and move like you would expect a big truck to move.

My setup is the first design (V belts) 6.2L diesel engine, TH400 tranny, NP208 chain drive transfer case, 10 bolt front and rear wtih 3.08 gears, and 33in tires.

with the tranny, gears, and tires, its hardley set up for performance, but i use it as a daily driver going to and from work, and i get 14-17 mpg depending on traffic and stoplights. and i get 20-23 mpg on the highway.

Its no rocket ship to be sure, but ive never had problems merging into traffic, and it'll get up and go to 55 mph fast enough for me.

I am however looking to put the Banks turbo kit on it, which is said to give big block level performance, but also boost gas mileage. the best of both worlds. Im also looking to swap in a built 700R4 with a NP205 at some point, although dreams of a six speed allison give me restless night sleep.

my vote goes for the 6.2L diesel, i bought one last october, and ive never looked back. and ive had several cars with gas powered 305 and 350's.