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Fuel economy of non-turbo 7.3 IDI?

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Old May 26, 2020 | 11:16 PM
  #31  
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well, it would IF it actually boosted Cetane.... market claims are lies.


do you remember Moose Juice ???
 
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Old May 26, 2020 | 11:23 PM
  #32  
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you know why we set IP timing to around 45 Cetane back in the late 80's because that was the general rating of the fuel back then.

Diesel is sold Based on BTU it costs more than regular gasoline because it has a higher BTU rating than gas... even though it is less refined and costs less to produce.

BTU equal ability to do work..... in a nutshell.

my 83 6.9 always got 20 Plus MPG up until 2005 when she was retired due to Cavitation
 
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Old May 26, 2020 | 11:40 PM
  #33  
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I do use diesel Kleen ... but I use half a bottle in each tank when I fill up... I exceed their recommended dose ... and I just bought a bottle of the DK water/alge eater to add to my tanks when I fill up in the next couple days..... do it work I don't know ... and does the DK Cetane booster work .... I have no evidence that it does..... BUT I will say I have no Fuel issues.
 
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Old May 27, 2020 | 02:51 AM
  #34  
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I understand the btu part, when I was running wmo 50/50 with diesel a few years back I gained a solid 1mpg even though the cetane rating had to of been alot lower..
 
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Old May 27, 2020 | 04:11 AM
  #35  
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as said, cetane booster is snake oil. kinda like k&n filter clean better than stock filters and give you better mileage.
people believe it because they trust what the manufacturers say. they think they do not lie to sell their product.
 
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Old May 27, 2020 | 03:01 PM
  #36  
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I want Good Snake oil.................but I ain't found any yet but K&N must be great as they charge 100 bux for a piece of foam and we all know $100 dollar foam is better than $.50 cent foam

who was that that said there was a sucker born every day ?????
 
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Old May 27, 2020 | 07:51 PM
  #37  
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got to agree the c6 isn't whats killing your gas mileage. its the rear gearing. going to 3.55 i avg 17mpg all day going 65. why becouse im not pegging the rpms with the 4.10 setup. the truck will not be as peppy on the low end anymore so its all give and take.
 
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Old May 27, 2020 | 11:46 PM
  #38  
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Originally Posted by gogereaver
got to agree the c6 isn't whats killing your gas mileage. its the rear gearing. going to 3.55 i avg 17mpg all day going 65. why becouse im not pegging the rpms with the 4.10 setup. the truck will not be as peppy on the low end anymore so its all give and take.
X2.

Even with my C6, I added a gearvendor OD and have the 3.55 axle. I get 21 mpg if I keep it under 60mph. I can get the high teens for fuel economy up to 80mph.

I understand the btu part, when I was running wmo 50/50 with diesel a few years back I gained a solid 1mpg even though the cetane rating had to of been alot lower.
.
I've been running WVO, and the power difference from diesel is negligible.
 
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Old May 28, 2020 | 02:00 AM
  #39  
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Originally Posted by genscripter
I've been running WVO, and the power difference from diesel is negligible.
Power felt the same to me, sure seemed to run quieter though, less clatter.

Just an fyi, at 55 a vehicle uses about 50% of it's energy fighting wind, at 70-75 you're using 75%

That's the real difference fuel economy differs so much between those speeds. It's a real shame the c6 didn't have a lockup converter, would have helped just a hair as well.
 
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Old May 28, 2020 | 02:26 AM
  #40  
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Originally Posted by DarkOverCast
It's a real shame the c6 didn't have a lockup converter, would have helped just a hair as well.
I put in a Hughes HD TC and that helped the MPG about a point.
 
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Old Dec 30, 2025 | 12:33 PM
  #41  
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Fuel economy

1987 Non turbo, stick 3/4 ton truck, stock everything. 21 mpg highway. Verified multiple times.
 
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Old Jan 8, 2026 | 03:23 PM
  #42  
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Originally Posted by Crappyfuelgauge
1987 Non turbo, stick 3/4 ton truck, stock everything. 21 mpg highway. Verified multiple times.
What gears do you have in it and is it 4x4? Zf5?
 
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Old Jan 8, 2026 | 11:04 PM
  #43  
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My 92 4X4 campervan (8400 lbs) gets 16 on the open road. It drops to about 14 while towing my race car over the mountains. It's due for injectors.
I usually use 15w40 Delo because Bi-Mart usually has the best prices on it.
 
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Old Jan 18, 2026 | 11:34 PM
  #44  
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Fuel Economy
85 6.9 with T19 4x4

18 average
15 low
23 high
 
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