MPG with Performance Mods

[99TanHoe]

I've done some searching and have found some references to MPG gains with some performance mods. My question is, what performance mods will also improve gas mileage?

So far the most popular seem to be:
Efans
Underdrive Pulleys
Electric water pump

For those of you that have done these mods, what kind of MPG gains did you see? Even if you did several mods at once, I would like to hear what kind of MPG results you got from whatever you did.

I saw alot of old threads dealing with Ewater pumps but the concensus was nobody had found one that would work with the Vortec. Has anyone found one for the Vortec?

My problem is, everybody I asked said that I would see a 1-2 MPG gain by swapping to 4.56 gears to handle my 315/70R17 tires. I haven't seen any MPG increase, if anything it got a little worse.

I did see a definite performance gain after installing the lower gears and the performance improved even more when I had a local guy tune it with a Laptop program but after 2 tank fulls of easy driving I have gotten identical 12.7mpg results. I stayed under 2000rpm for the most part. With my setup 65mph = about 2150rpm, so you can see I have been really babying it to stay below 2000rpm.

Is that the best I can expect from a stock 350 Vortec? The Hoe was already lifted when I bought it so I don't know what kind of gas mileage it got without the lift and oversize tires.

Also, I have the Autotrac transfer case. Could that be the poor gas mileage culprit, since it turns the front drive shaft all the time even in 2wd?

I know there are some of you that have your Hoe's setup similar to mine, how is your gas mileage?

My older Hoe (stock 95' TBI) with 3.73 gears and 265/75R16 tires gets a solid 14mpg and sometimes a little better. I know comparing the nonlifted TBI to a lifted Vortec is like comparing apples to oranges but I was hoping the Vortec would do better.

 

[Trippers99hoe]

My stock hoe gets 16.5 hwy(actually got that for an average on a 3000 mile vacation)
But around town(back n forth to work etc. ) 10 to 13 mpg.

285/75/16 tires 3.73 gears w/autotrac

These trucks are heavy and not very aerodynamic and lifted just makes it worse ....

 

[metalemt]

In 2wd your front wheels should be disengaged, in auto or 4hi it will be engaged. I just installed cold air intake and saw an additional 40-60 miles per tank depending on how good I am, and I'm not really that conservative on the skinny pedal, saw a slight increase with my exhaust as well

 

[99TanHoe]

My stock hoe gets 16.5 hwy(actually got that for an average on a 3000 mile vacation)
But around town(back n forth to work etc. ) 10 to 13 mpg.

285/75/16 tires 3.73 gears w/autotrac

These trucks are heavy and not very aerodynamic and lifted just makes it worse ....

Thanks Tripper,

Your mpg figures are what I was looking for. Its interesting how a stock vortec performs compared to a stock TBI. As I mentioned above my 95' Hoe gets 14mpg with mixed driving and it has 3.73 gears. In 4 years I never did take the TBI Hoe on a Hwy trip so I don't know how it would do. I do have a TBI 3/4 ton GMC pickup that would get close to 16 on hwy trips.

The 99' Vortec definitely has more power than the 95' TBI. I was just hoping for a little better mpg along with the increase in power.

Your right these trucks are heavy. I know all too well I've been driving this generation of truck/Tahoe since 1996. I love the dependability of them and when you do have to work on them parts are affordable.

---------- Post added at 07:31 AM ---------- Previous post was at 07:24 AM ----------

In 2wd your front wheels should be disengaged, in auto or 4hi it will be engaged. I just installed cold air intake and saw an additional 40-60 miles per tank depending on how good I am, and I'm not really that conservative on the skinny pedal, saw a slight increase with my exhaust as well

Thanks Paul

I've been learning alot here and on other forums about the autotrac. The thing that bugs me the most is not knowing/understanding something.

I've been looking at the Volant, looks like a good design improvement over stock. The reduction of duct bends was a smart idea. The 99' Hoe already has a dual in, dual out 50 series flowmaster. I've been thinking about changing to a magnaflow.

 

[stereodesigner]

My 96 Vortec on 255/75/17s is getting 16 city (15 if I'm flooring it around town)
Only mod I have is true dual exhaust.......did a tune up and keep all the fluids changed

Sent from my DROID X2 using Tapatalk 2

 

[99TanHoe]

My 96 Vortec on 255/75/17s is getting 16 city (15 if I'm flooring it around town)
Only mod I have is true dual exhaust.......did a tune up and keep all the fluids changed

Sent from my DROID X2 using Tapatalk 2

Yea, if you throw out the hard to believe high responses and the truthful lead footed low responses, the general consensus on this and other forums seems to be 15-16mpg with a stock Vortec and mostly Hwy use. Most responders have some mods, some like you have very few if any.

It appears that you would have to install quite a few of the mods to make an appreciable gain in mpg. Then you have to consider the total cost of those mods verses just paying a little extra for gas with no mods. Now if the mods actually provide some power then that's something else to consider.

I did the math already and considering the average of 15,000 miles per year driven, with gas costing $3.25 per gallon and a 1mpg difference in mileage it would only cost, I think is was about $250 a year more in gas. A high quality cold air intake costs that much or more. So maybe 1 mod a year, if HP is gained, would be sensible strictly from a $$ standpoint. If your looking a seat of the pants standpoint, now that's a different story.

 

[retorq]

So far the most popular seem to be:
Efans
Underdrive Pulleys
Electric water pump

I saw alot of old threads dealing with Ewater pumps but the concensus was nobody had found one that would work with the Vortec. Has anyone found one for the Vortec?

Any of them will bolt up, you need to address the coolant crossover. If you removed the heater valve at the firewall and ran coolant thru the heater core full time (ie. hot fluid going thru the heater core in the summer decreasing efficiency of the AC system) and returned it to the radiator it would work. Is it worth it?? No. I did this on my 95 with Vortec heads and ended up eventually going back to a performance mechanical pump.

 

[99TanHoe]

Any of them will bolt up, you need to address the coolant crossover. If you removed the heater valve at the firewall and ran coolant thru the heater core full time (ie. hot fluid going thru the heater core in the summer decreasing efficiency of the AC system) and returned it to the radiator it would work. Is it worth it?? No. I did this on my 95 with Vortec heads and ended up eventually going back to a performance mechanical pump.

Thanks retorq

It sounded like a good idea but there just wasn't much information on it. I'll mark that one off the list.

 

[stereodesigner]

I'm doing headers and possibly different distributor hopefully give me some good news

Sent from my DROID X2 using Tapatalk 2

 

[JubjubW]

ever check the gas your putting in? Of course you have to weigh the costs but theres a couple stations around my town that sell all grades with no ethanol which, from what I can remember, i almost doubled my gas milage.

On a 180 mile round trip (mostly highway) i was averaging 25-26 MPG with newer plugs (iridiums), hi perf wires, factory cap and rotor (tried changing those before the trip but the truck started bucking really bad so I put the original ones on) and synthetic oil, and truck with 210,000 miles on it and no real mechanical fixes (ei - original wheel bearings, control arms, etc it needs some work but still the tires werent perfectly in line AND they are oversized for hauling offroad)

EDIT

I just realized im getting almost the same milage as my wife's 2007 Mazda CX-7 - Turbo 4 banger she has a tiny gas tank and is constantly filling up with that thing