bp71k5
3/4 ton status
The weight of bigger tires more than cancels out any gearing problem. Don't ask how I know. 
Just drive downhill all the time.
Just drive downhill all the time.
CK5
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improving gas mileage
- Thread starter mwood1985
- Start date
ljense8
Registered Member
drew4x4
1/2 ton status
like its been said, the biggest thing that will help you save fuel at 65 mph is an overdrive unit. either swap to an nv4500, or an overdrive box, that will help you at highway speeds... but it'll still only be saving you pennies at the pump because you can only expect a few more miles per gallon. its still a heavy truck even with OD.
an LS swap can bump up your mileage too.
an LS swap can bump up your mileage too.
Jessie James
1/2 ton status
The bottom line is that you want to save money, right?
Well, the solution is to NOT spend money.
If you spend $500 on a transmission (or something else), you've just wasted that money which could have been used for gasoline. $500 probably buys you more than 160 gallons of gas. Throwing money at getting better MPG is backwards. Driving slower is always more effective - it costs you nothing but increases fuel efficiency.
Let us say you buy a new transmission for $500, and you increase your MPG from 10 mpg to 11 mpg. That is a 10% increase in MPG, which would be pretty big in the scheme of things.
If that cost you $500, and gas costs $3.00 a gallon, and you have a 30 gallon tank, that means you can now go 330 miles instead of 300 on a fill-up. So each fill up you are "gaining" about 3 gallons of gas, or saving about $8.
To make up for your $500 spent, you have to fill up your tank 62 times. So 30 gallons x $3.00/gal x 62 = $5,580 you have to spend in fill ups before you break even with the MPG you have gained versus the money you spent. Let's say you fill up 2 times a month, that means you have to fill up your truck for 2.5 years before you "break even".
Spend $1000 and double that. 5 years to break even. It's not worth throwing money at.
Will this be different if you are getting 3 mpg and you can get 6 mog? Sure, you've just doubled your MPG, but you still have to consider the costs spent.
You could probably save more money each month by changing your cell phone or cable TV plan, or lowering the thermostat setting in your house ... or stop buying lunch out every day.
All I am saying is there are better ways to save money. Drive slower is what I do.
Well, the solution is to NOT spend money.
If you spend $500 on a transmission (or something else), you've just wasted that money which could have been used for gasoline. $500 probably buys you more than 160 gallons of gas. Throwing money at getting better MPG is backwards. Driving slower is always more effective - it costs you nothing but increases fuel efficiency.
Let us say you buy a new transmission for $500, and you increase your MPG from 10 mpg to 11 mpg. That is a 10% increase in MPG, which would be pretty big in the scheme of things.
If that cost you $500, and gas costs $3.00 a gallon, and you have a 30 gallon tank, that means you can now go 330 miles instead of 300 on a fill-up. So each fill up you are "gaining" about 3 gallons of gas, or saving about $8.
To make up for your $500 spent, you have to fill up your tank 62 times. So 30 gallons x $3.00/gal x 62 = $5,580 you have to spend in fill ups before you break even with the MPG you have gained versus the money you spent. Let's say you fill up 2 times a month, that means you have to fill up your truck for 2.5 years before you "break even".
Spend $1000 and double that. 5 years to break even. It's not worth throwing money at.
Will this be different if you are getting 3 mpg and you can get 6 mog? Sure, you've just doubled your MPG, but you still have to consider the costs spent.
You could probably save more money each month by changing your cell phone or cable TV plan, or lowering the thermostat setting in your house ... or stop buying lunch out every day.
All I am saying is there are better ways to save money. Drive slower is what I do.
I keyed in early that he just doesn't like pulling over, cost of fuel isn't that big of a deal. But from having looked at them, $500 for an OD unit is crazy low. If manual, a gearvendors unit is $3000, an NV4500 swap is easily $1500. You are correct, it would take a TON of driving to ever recoup the costs. You really have to justify it some other way...less engine noise, better gear spread, something other than just economy. Fuel injection swaps are the same way...even at 1MPG extra, it will take a LONG time to recoup the cost, let alone if you put some value on your time.
As mentioned earlier with the 4BT, if you don't want to stop for fuel, swap in a diesel. 25MPG is completely possible. The range alone from that swap would make it ideal, you figure even ~17MPG off-road you would be around 476 miles (leaving couple gallons as reserve), I don't think many of us would need that much even for a week long trip off-road.
As mentioned earlier with the 4BT, if you don't want to stop for fuel, swap in a diesel. 25MPG is completely possible. The range alone from that swap would make it ideal, you figure even ~17MPG off-road you would be around 476 miles (leaving couple gallons as reserve), I don't think many of us would need that much even for a week long trip off-road.
Jessie James
1/2 ton status
The smarter thing to do, IMO, would be to sell the current truck and use those proceeds to buy a truck that was diesel by design. You would spend a lot less money (not to mention the hassle of doing a swap) and get instant results.
Funny thing is, other than a 6.2L truck (which aren't common outside of the CUCV's) I am not sure any "factory" full size truck (diesel or no) gets ~25MPG, even currently. I suspect it's highly unlikely in a SFA rig.
I personally like this body style, and my truck, so swapping a "better" engine in is the only way *I* would be able to do this sort of thing. I'm sure many of us are that way...I could get a newer chev with an LS-series or 6.5 Diesel with an OD manual trans, but it would be IFS, and I don't like the body style.
I personally like this body style, and my truck, so swapping a "better" engine in is the only way *I* would be able to do this sort of thing. I'm sure many of us are that way...I could get a newer chev with an LS-series or 6.5 Diesel with an OD manual trans, but it would be IFS, and I don't like the body style.
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chulisohombre
1/2 ton status
If you aren't worried About money or Working over the truck, get a nv4500 and you have overdrive and will have a higher 1st gear. No more granny but a better split to not have to hold the engine at a high rpm at speed and shifting like the 465. You would get at least 30 To 40 miles extra out of that and push out your stop for gas out a lil bit.
black dawg
1/2 ton status
A diesel swap wont help nearly as much as it should, with that gearing. Mpg falls off pretty sharp above 2k with just about any diesel.
My suburban, originally 6.2 700r4 and 3.73 gears, would get 16ish in town and 20-21 on the highway. After I swapped in the th400 mpg dropped to 13 in town and 15-16 driving under 65 on the highway.
I am betting the jetting in the carb needs gone over. My 80 burb 350/465 and 4.11 gears with stock tires put down a solid 13 with the carb jetted right.
My suburban, originally 6.2 700r4 and 3.73 gears, would get 16ish in town and 20-21 on the highway. After I swapped in the th400 mpg dropped to 13 in town and 15-16 driving under 65 on the highway.
I am betting the jetting in the carb needs gone over. My 80 burb 350/465 and 4.11 gears with stock tires put down a solid 13 with the carb jetted right.
Dorian says no, but I say it depends. A carefully tuned Quadrajet will deliver fuel economy similar to a TBI setup. None of us know how your Edelbrock is set up and I don't know of anybody who can tune a carb for max economy by ear. This would still require a dyno or a driving around for a while with a WBO2 setup.
Standard logic applies. The biggest things you can do are make sure everything is running as it should and drive slow. Then weigh out your overall plan and potential savings before spending money. "Trying out" a lot of little things can end up costing more than a more effective big ticket item.
I agree that buying another vehicle that gets better mileage as-is will be cheaper and quicker than fixing up what you have, but I know it's easy to be attached to a vehicle and it's hard not to change things when you know they can be better. That's OK, too - just be honest with yourself that the upgrades are an expense to help you enjoy the vehicle more and not an investment.
If range was really the only issue, you would just add a 2nd tank and be done.
mwood1985
1/2 ton status
8 to 10 criusing. she got 18 today on the way back from Canton ga
lol had to trailer her back home
i postes another thread but we had a accident of a ****ty spotter and laid her on her side when he didnt set an angle up right. i eased down a bank and over she went
lol had to trailer her back home
i postes another thread but we had a accident of a ****ty spotter and laid her on her side when he didnt set an angle up right. i eased down a bank and over she wentcrawlink5
1/2 ton status
No, I had to get a diesel fuel tank for a 6.2 K5 that was 25 gallons. 600 and change. But the around town mileage is not as good obviously.
Only 600? lol.
I don't disagree on TBI vs. carb for mileage, both need tuned to run optimally. But speaking strictly freeway, between those two methods of fueling, the difference is going to be minimal, assuming both are tuned properly. That is a very narrow portion of engine operation, and is why I believe it to be true.
I am *very* obsessive on measuring economy every single tank, and if TPI (which is theoretically more efficient than TBI or a carb) can't net me any better mileage on the freeway than a carb, I believe factors acting on economy are far less based on induction, and more on the things that are almost impossible to change on a truck. Again, weight, drag, displacement.
I don't disagree on TBI vs. carb for mileage, both need tuned to run optimally. But speaking strictly freeway, between those two methods of fueling, the difference is going to be minimal, assuming both are tuned properly. That is a very narrow portion of engine operation, and is why I believe it to be true.
I am *very* obsessive on measuring economy every single tank, and if TPI (which is theoretically more efficient than TBI or a carb) can't net me any better mileage on the freeway than a carb, I believe factors acting on economy are far less based on induction, and more on the things that are almost impossible to change on a truck. Again, weight, drag, displacement.
In regards to installing larger tires, while you may be able to optimize the cruising RPM for fuel economy the larger tires will likely completely counteract any gain. Larger tires are heavier with more rolling resistance and the added height will raise the vehicle and create more aerodynamic drag. Heck, while the engine may be operating at a more efficient RPM you may even lose MPG because of the tires. I will say that going from a bias ply TSL to a lighter and less aggressive radial would help MPG.
For aerodynamic resistance the larger the frontal profile of the vehicle is the more drag you will have. This is measured from the ground up to the top of the vehicle.....more lift or taller tires increases this.
For aerodynamic resistance the larger the frontal profile of the vehicle is the more drag you will have. This is measured from the ground up to the top of the vehicle.....more lift or taller tires increases this.
I think this is true, up to a point. Once a vehicle gets X inches/feet off the ground, drag isn't going to change.
A truck lifted 4 feet is going to have very little more drag than if it were lifted 8"...you aren't exposing anything to more airflow EXCEPT the tires in that case.
I don't know at what point the ground ceases to be a factor in drag, but at some point, the ground is going to be too far away to affect airflow.
I get 24mpg hand calculated with my Tahoe rocking an LB7 Duramax and a 6 speed manual transmission. Thats with 37s and 5.13s (aka, I'd do much better with less gearing, she spins too fast right now on the freeway)
That's pretty impressive. I'm assuming that's not a factory setup in the Tahoe? Either way, 20MPG looks to be the best "rated" MPG with the 6.5L, so you are doing good in any case!
So many people talk about horrible mileage even with the new diesels, they must just be that bad of drivers.
So many people talk about horrible mileage even with the new diesels, they must just be that bad of drivers.
Jessie James
1/2 ton status
You're getting 18mpg and you want MORE? That's about the best MPG I've seen any member post.
I think the tow rig got 18 with the K5 on the trailer, which would be pretty impressive. Either that or he got 9MPG on the way out and averaging that with a "no fuel" return trip nets 18 round trip.
