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6.2 GM Diesel


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#1 jmodge

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Posted 10 January 2019 - 01:57 PM

Greetings from the other side! I am curious if anyone on the site travels using a 6.2 diesel. If so, what kind of fuel mileage do you get with the camper on? Thanks


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#2 Zoomad

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Posted 18 January 2019 - 04:49 AM

Greetings from the other side! I am curious if anyone on the site travels using a 6.2 diesel. If so, what kind of fuel mileage do you get with the camper on? Thanks

Is your K5 a diesel?   I've had a couple crazy thoughts about a 6.2 due to the fuel mileage but I can't get over the problems the 6.2 is well known for.   In my case with the lift/tires/gearing and the added weight/drag of the FWC I can only imagine how it would chug along.  Sure a Banks sidewinder can perk it up, but not enough.  Throw in the terrain I'm used to traveling in (the Rockies) and I'd be getting passed by loaded VW microbuses.   

 

The big block plan is fully in the parts procurement phase, fuel mileage be damned.  I need to be able run the speed limit on the passes.  As it is, the mileage will probably be on par with the 5.3 I have in there.  But the engine won't get whipped like a rented mule when the road goes up in elevation.  


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#3 jmodge

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Posted 18 January 2019 - 11:24 AM

 I have the original 5.7, I installed vortec heads, low rpm cam, and an electric fan. I bought an '85 K5 with a 6.2 figuring to do a swap strictly for fuel mileage. Since then the price of diesel and gas went opposite direction. I was just wondering if there was anybody carrying a FWC camper with a 6.2, there is a wide range of claimed fuel mileage out there.

  :unsure: Wouldn't want to get caught from behind on a mountain road by a large truck, that's for sure :o They have a very narrow powerband, damn strong for a couple hundred rpm though, which would work good for us as we putt backroads a lot here. It would be a lot of work and I am leaning toward the idea not being worth it. I like using it more than working on it :D One of these years I would like to make it out to the FWC gtg out there.

 I can't coax quite 13mpg out of my small block


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#4 ntsqd

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Posted 18 January 2019 - 02:07 PM

If you can live with the NA 6.2 I'd drive it as-is.

 

I couldn't.

 

I've been semi-sort of on the look-out for a 6.5tD donor for a project vehicle of mine. I think they're a little in over their heads when put in a 3/4t or 1t, but in what essentially is a SuperCab short-bed Early Bronco I think it would work very well. And weigh a lot less than a 6.9L or 7.3 IDI.


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Thom

Where does that road go?

#5 jmodge

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Posted 18 January 2019 - 04:20 PM

If you can live with the NA 6.2 I'd drive it as-is.

 

I couldn't.

 

I've been semi-sort of on the look-out for a 6.5tD donor for a project vehicle of mine. I think they're a little in over their heads when put in a 3/4t or 1t, but in what essentially is a SuperCab short-bed Early Bronco I think it would work very well. And weigh a lot less than a 6.9L or 7.3 IDI.

The 6.2 I have is in a rusted untitled k5 that is on a friends hunting property. Runs great and has everything needed for a swap outside of upgrades. Just curious about others experience carrying a FWC with one. So far no real life feedback. If I don't hear something by spring, I guess that tells me not many dinosaurs running those dinosaurs. :D


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#6 Zoomad

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Posted 19 January 2019 - 04:40 AM

I've collected a serious amount of Blazer FWC camper photos since obtaining mine.  One reason to document the differences, reference for my build and looking how else it's been done.  I don't think I can recall any of them being powered by a 6.2.   It's not to say it can't be done, but I don't remember seeing it.  

 

Just going off of what I've heard talking from other Blazer guys, I've heard 20mpg possible with one in a lifted truck with 35" tires and proper gearing for the tires.  So often the gearing really gets overlooked and undergearing one just makes it that much more sluggish.  Granted that's not a fair comparison to the load of the FWC and the aero drag, but it's close.

 

If it's just for running around your home state of MI, it may not be the issue I would have out here in CO.   Less altitude and less grades for sure.  

 

I just don't know that the 6.2 is going to net a stellar mileage gain over what the small block is already doing.  At least it's not a big enough gain to warrant the change.  

 

At 13mpg with the small block I think you are doing pretty good.  Also, even though diesel has come down it will go back up. Since they have to refine it more to get to the ultra-low sulfur standard, the price will always be higher than before.   That also brings the point up that the 6.2 was never intended to be run without the sulfur in the fuel.  The sulfur is was gave the fuel it's lubricity for the injection pump and injectors.   Take that away and run the pump without it and it will fail.  Fuel additives can be added to give the lubricity back to the fuel, but it's an every tank scenario that would need to be factored into the fuel costs.  

 

I'm curious about the rest of the setup just to see if there are any areas some gains could be made.  Still running a carb or TBI?   OD trans? Gearing? Tire size?   Depending on what you have there could be some left on the table, probably not monumental gains but every little bit helps.  


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#7 jmodge

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Posted 19 January 2019 - 12:51 PM

31" tires @ 50lb, 3.73 gears, 700r4, vortec heads, flex-a-lite dual fans, tbi w/gm performance intake. I have heard some pretty outrageous claims on mileage for the 6.2, 20mpg sounds doable. I can get about 12.5 babying it on a steady cruise. It is usually a little less.Having the aerodynamics of a block of lead doesn't help :)

 Price of diesel used to be lower than gas, but I don't think we will see that anymore. I heard the nautical shipping industry has been regulated to use a more refined diesel fuel and if true that would change the supply and demand. I worked fleet maintenance for a municipality and up until a couple years ago we ran off road diesel in all our trucks. That could have been out of ignorance, our director had an engineering degree in concrete. Intelligent guy but definately a fish out of water.

 Anyway, 19 or 20 mpg is probably not a good enough savings unless I plan on putting megamiles on the truck. Easier on my body to leave it alone too, I just diesels I guess.


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#8 Zoomad

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Posted 19 January 2019 - 02:56 PM

Just comparing your gearing and tire size, in OD you are pulling nearly the same RPM at 65 that I am (1850).  I'm running 4.10's with the same trans and 315-75/16 tires which measure out to a little over 34.5".  In my case the 5.3 is well under the torque peak and why I'm lacking power on grades unless I carry momentum or pull it out of OD earlier to keep the engine rpm's up.

 

Your setup is probably building torque a little lower in the RPM band than mine is.  With the tire size you run and the gearing it's probably pretty close to ideal.  Jumping to 4.10's would bump the cruise RPM to 2000 at 65 mph and might keep the engine closer to it's peak torque which might net a little mileage gain.  I know that sounds backwards as going steeper in gearing usually cost fuel economy, but running well below peak torque is requiring the trans to kick down to lower gears anyway to maintain speed if you are pushing a headwind, hill or just trying to pass a slower car in front of you.  I just don't think the expense of changing gearing is going to be worth the slight MPG bump.  Again, like you said you would have to put megamiles on the truck to justify the expense to get the fuel savings.  

 

I'm a bit of a nerd when it comes to tracking fuel economy on mine.  Down to the point of using an app to track it on my phone.  For an example here is some of my data over 63 refuelings in 611 days I've spend $2,672.00 in fuel, costing me $4.37 per day to run it at a per mile cost of $0.25.   Put into perspective, it's still not cheap but for what I can do and where I can go with it (away from crowds of people at normal RV campsites) the price is totally worth it.   

 

Here's some more nerd worthy data.   Since I've been tracking I've poured 997 gallons of fuel down the gullet at a total average 10.72 mpg.   Highest mpg I pulled was 23.03 (stock top, no camper), lowest was 5.87 (with camper, winds and heavy right foot) and the last tank was 9.68.   Highest I've pulled with the camper was 16 and I honestly have no clue how I pulled it off.  It was on the Desert trip last year on our blitz to get to Kingman AZ from southern Colorado in one day.  

 

Point being, these trucks without campers weren't known to be stellar on fuel economy.  Add the aerodynamic greatness that is about as good as a barn door or drive in movie screen and the mileage is going to fall.  I think at even 12 mpg you are doing pretty good with your terrain.   Mine would do better down there for sure.  You could be driving a class A motorhome with a V10 ford (all that is out today for gassers) getting 8 mpg in a 38ft coach and relegated to campsites with more class A's, 5th wheels and travel trailers and the scores of people that go with them.  Or you are driving one of the coolest little homes on wheels getting out to spots where the masses can only dream of. All the while still spending less on fuel than those people are.   

 

My hope is going to the big block in my case the power is where I need it.  This way grades aren't the chore that they are now.  If my Buddy's 8.1 K10 with the Phoenix camper can consistently get 13 on the highway with his at 8,000 pounds loaded, I'll probably have an improvement in mileage over what I have now.  Not a big one, but better than the average I'm pulling now.  


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#9 jmodge

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Posted 19 January 2019 - 06:35 PM

 The cam I put in starts power @ 600 rpm with a low torque curve. Trans is switched to hydraulic lockup and cruises pretty good, but cruising range is above the rpm I drive on the highway. But, we are rarely on the highway. I have a fuel log that dates back to early 2014 when I made my changes. I don't know where the older one is, if I had one. It seems I did. Towing with it really drops fuel mileage. But like you say, there is definately something special about it. Took me nearly two years to discover then find one I wanted.something that I could hall wood with, navigate my dump trailer in my narrow lot, 4wd, and fit under an 8' garage door. It fits the bill. In the end I will probably just keep going forward with it the way it is. I may get a tunercat or tunerpro program and fart around with timing curves fueling a bit.

 Have you ever considered a 6 liter? Being an LS like your 5.3 would make it a simple swap wouldn't it? They do like to rev more than the conventional big block though.

 Next trip I go on I am going to track my mileage by gps instead of the speedo. Hopefully I will feel better not worse. Lol.

 

 I saw quite a few of these rigs while I was looking, as well as after also. I had to quit looking because I kept having the urge to fly out west and grab another. One still sticks in my mind and it was probably 6 years ago! In the Colorado mountains for $1500 with a newer camper than mine :D Oh well, it's winter, I retired, and I think of making work for myself. Gotta quit that. Think I will load up the K5 and quad and go check my game camera this week.


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#10 ntsqd

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Posted 19 January 2019 - 08:22 PM

Used to own a '91 Sub 1500 TBI 5.7L (tired, but not used up), 700R4, 8 lug front conversion & a rear 14bff (w/ Detroit), 3.73's with about 3" of lift, and 285/75R16's

 

I don't check mileage as a rule. Usually spot check it on random occasions. One trip that required heavy right foot to meet someone elses timeline, and she was late getting out of the gate, saw about an 80 mph average and a very, very surprisingly 16 mpg. Checked it 6 ways from Sunday and still got the same results. More normally it was 12-13. I concluded that 80 put it at the RPM where the engine ran enough more efficient that it more than offset the increase in drag from the higher ground speed.

 

Re-gearing was not in the cards for that vehicle, so I lived with it.

 

I've driven an NA diesel just far enough to know that I never what to do that again. Turbo-diesels only for me.


Edited by ntsqd, 19 January 2019 - 08:24 PM.

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Thom

Where does that road go?




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