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To 6.5 or not to 6.5?

R

REWunderkind

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Full disclosure: I'm a brand new member and I've never owned a diesel before. I have family and in-laws who have been giving me advice and most of them tell me to stay away from the 6.5. Thing is, I just started a business and need a vehicle that can get me 75 miles to and from work in MN winters, haul construction materials, tow the occasional trailer, and not break the bank - either on purchase or on fuel. I've done the math - 50,000+ miles per year at 20 mpg diesel is about the same as 15 mpg gas, but diesel prices are more stable and we know gas isn't going to stay at $1.90 per gallon...

Long story short, I don't have a lot to invest in a vehicle this year. All the money is going to buying real estate for the business. I've found a 99 Suburban with a 6.5 and 201k miles and a 98 Sierra 3500 crew cab long box with 270k. Both are in the price range AND could haul my whole family comfortably, plus they're in okay to decent condition. I can find some beat-up old Powerstrokes with 300,000+, but fuel economy isn't as good from what I hear and my legs are too damn long to fit a car seat behind me in an extended cab.

What do I need to look for when I go test drive these rigs? I know my way around a gas engine fairly well and I'm relatively mechanically inclined. I just need some guidance when it comes to the fairer fuel - and in particular, the affordable 6.5. Thank you for your time and consideration.
 
What kind of prices are you looking at?

Check for blow by. Open the engine oil fill cap with the engine warm and running.

Both will need timing gears at some point. In my opinion 270,000 miles is getting to the time of changing the timing chain and gears to timing gears.

I ran one truck 500,000 miles and I was surprised it still ran as lose as the chain was.

Check engine oil cooler lines - That is a must fix id they are leaking - do not replace with OEM style lines. Go with something like leroydiesel.com or lubricationspecialist.com sells

leroy is the place to go for everything that he sells. He does sell some stuff that is not on his website.

Check to see if they have a 4" exhaust or any other upgrades.

What condition is the Suburban in body and interior wise? If you are not interested, I might be

If you are nice to a 6.5 they are usually nice to you. We have an average of over 300,000 miles on our vehicles now.

I install a Fluidamper and bypass filter on every vehicle. I run Amsoil 5w30 at 20,000 mile oil changes
 
REWunderkind said:
I've done the math - 50,000+ miles per year at 20 mpg diesel is about the same as 15 mpg gas...
Click to expand...

Gonna stop you right there with a word from WarWagon's school of hard knocks. The Textbook required reading is linked below. :bookworm:

Only NA engines get close or in 2WD trim go over 20MPG. Otherwise your figures are garbage for a typical 15 MPG tops 6.5 Turbo Diesel in auto trans 4x4 trim. It's better than the 9MPG 454, yes. Then you hook a trailer and can get as low as 7MPG on grades. You would want the 'can't get out of it's own way' 6.2NA (Needs A turbo) engine for the 20 MPG figure.

The 6.5 requires more maintenance to eat up any fuel savings. Modern 1/2 ton pickups can return 18MPG or better and have 5-10K oil changes. The 6.5 HD use is 2500 mile oil changes, yes under 3000 miles. Fuel filters, 2 batteries vs. 1... Better tax write off on a new vehicle.

Not knowing ANYTHING about diesels, or the 6.5, and expecting 140 miles a day is setting yourself up for a big expense by people who can't or don't want to repair the 6.5TD. Further showing up in a old worn out vehicle (let alone a stinking IDI diesel) says your business isn't doing well and customers question long term warranty at the least affecting the price you command and at the worst a wasted trip. It is a rough situation to learn to fix a 6.5 under fire needing the damn thing the next day for work. Parts are around, but, hard to find in good quality. Been there done that and rented things to keep the delivery route I was on.

Car seat IS NOT a concern for a business vehicle. If it is you have to split mileage and personal use on your taxes - best answer in a IRS audit is 'I own another vehicle for personal use' while NOT showing up in the business vehicle that has a car seat in it.

You would be better off with a pickup, crew cab if the car seat mess can't be avoided, with a larger 5.3 gas V8 and get rid of it before it hits 100,000 miles. Expenses for repair add up quick over 100K on any vehicle. Buy less property for the business because you can't drive a store. Have a slush fund for a rental pickup if yours breaks down for a couple weeks.

New stripped down 1/2 ton pickups are $25,000 give or take. That's only $15,000.00 more than you will spend buying a 15-30 year old vehicle and repairing it plus downtime. 250,000 miles is 2.5 lifetimes. EVERYTHING is wearing out that hasn't been replaced outside the engine. Age is an issue.

I suggest you move closer to your business as that is a lot of expensive miles in bad weather. Figure the full 50 cents or so a mile the IRS gives you. Just saying.

Give you an idea of what's needed on a 6.5 to run hard and I do my own work without paying a shop $100 an hour:

Textbook: http://www.maxxtorque.com/2012/07/the-65l-diesel-factory-equipped-asthma.html

Now as a hobby rig or if you do your own heavy work a high mile vehicle can be like an alcoholic owning a bar. Lots of time under the hood. Now I do take my 6.5 anywhere, can and have changed the engine for $2000.00, etc and likely have $15,000 in the damn thing. The 6.5 isn't known for long life like Cummins engines are, but, do ok vs. a gas engine. As for diesel reputation until you make some changes not so good.

So welcome and we are here for you if you want to try taking the hard road of a 6.5.
 
Yeah, whenever someone says they are getting 20+ mpg out of their diesel, chances are they are over exaggerating, can't calculate mpg correctly, or are just flat out lying. I've never had any diesel (Duramax, 6.5, 6.2) ever get better than 15 mpg....with the exception of my k2500 suburban. It was getting 18mpg when I got it. I have no idea what I did to make it hate me, but now I'm lucky if I see 15.

I should mention that I tow a lot with my diesels, with the exception to my suburban. And they have all always averaged in the 12-13 mpg, in stock form, in modified form, with stock tires, or with larger tires, they all seem to get around the same mpg regardless.


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In all honesty, if you don't know much about diesels and won't be hauling much with it, you would probably be better off finding a vortec 350 mid to late 90s truck. Relatively similar fuel mileage, pretty maintenance free (compared to a diesel), and any half competent mechanic can work on it. I have two diesels and wouldn't trade them for their gas counterparts, but I also have a gas truck that I am finishing up to be my daily driver/work truck.


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My 94 stock netted about 14 mpg out in the sticks. After my engine rebuild, trans rebuild and pretty extensive mods i regularly got 18 in the sticks. (Sticks are hilly 55 mph roads).

Upkeep is something that needs to be factored in over a gas job that often eats the difference in MPG plus like WW said.

But the 6.5L is definitely the cheapest (I mean lowest cost) diesel to own if properly maintained.

Out of the 5 years i plowed with my 6.5L, it was broke down for 1 snow storm. I was doing a inspection and found the turbo to have excessive play and could touch the housing. So i had to overnight a new center cartridge for my Holset WH1C. Replaced in my un-insulated garage with temps below 0 degrees F!

You really need to learn about these truck extensively before you purchase. Or know a very competent 6.5L (let me tell you, its not easy to find a dinosaur that knows these) mechanic and afford to pay him.

Mine was a 94 RC/LB 4x4 with 3.42 gears.
 
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Fuel economy has gone down since they changed the diesel. When I first got our 98 Suburban, I averaged 18 mpg pulling a camper home from Pennsylvania.

The 1994 K3500 averaged 18 mpg before I installed the ladder rack and side boxes. Now it get's 16 mpg.

I've never got worse than 12 mpg.

I have never noticed the huge maintenance expense. Except with our fricking 2006 Jeep Liberty CRD - Hate that thing. The most expensive vehicle I have ever owned. Timing belt every 70,000 miles and now it's starting to rust.

I see a lot of newer vehicles rusting away and our old GMT400's are still hanging in there
 
A person should also check the station where they get there fuel with a container.

At one station I put 5.4 gallons in each 5 gallon container and at another I put 6 gallons in the same containers.

I've never seen the pumps be off in the customer's favor
 
DieselSlug said:
My 94 stock netted about 14 mpg out in the sticks. After my engine rebuild, trans rebuild and pretty extensive mods i regularly got 18 in the sticks. (Sticks are hilly 55 mph roads).

Upkeep is something that needs to be factored in over a gas job that often eats the difference in MPG plus like WW said.

But the 6.5L is definitely the cheapest (I mean lowest cost) diesel to own if properly maintained.

Out of the 5 years i plowed with my 6.5L, it was broke down for 1 snow storm. I was doing a inspection and found the turbo to have excessive play and could touch the housing. So i had to overnight a new center cartridge for my Holset WH1C. Replaced in my un-insulated garage with temps below 0 degrees F!

You really need to learn about these truck extensively before you purchase. Or know a very competent 6.5L (let me tell you, its not easy to find a dinosaur that knows these) mechanic and afford to pay him.

Mine was a 94 RC/LB 4x4 with 3.42 gears.
Click to expand...


Even if not properly maintained military surplus 6.2 engines (A 6.5 is simply a bored out 6.2) are available cheaply, injectors are around $550 a set, and yes, the simplest and lowest parts cost diesel. The PMD on electronic injection pumps, 1994+ years, are a known known and solved with a made in USA extension cable and new PMD on the bumper. The aftermarket has caught up with the 6.5 esp. it's need for a better turbo than OEM, PMD solutions, better lift pump, and a better Harmonic Damper.
 
I figure on investing another 2 -$3000 after I buy a 6.5 For the extras I want.

Right now we are looking for a 1999 crew cab truck. My wife doesn't like the NV4500 - 5 speed manual in the 1994.

I've always preferred manual transmissions. Since I do not put miles on like I used to, I'm starting to be coerced.
 
Agree with the others that jumping into a stock (or nearly stock) 6.5 and expecting to keep it out of the shop is not the best plan. Consider scaling back a just a bit on the RE purchases and changing the vehicle line-up:
> Used Tundra for the reliability factor, or a Sequoia.
> The Burb presuming it is a 3/4 ton (2500), has a 3.73 rear, and locking rear.

Point is that the 6.5 is a reliable and lower TCO platform *after* putting some money into it. For a reference point, IIRC a *new* P-400 long block (a better 6.5 block from AM General) is about the same price as a set of DMax fuel injectors. As mentioned, you will need to learn about the 6.5 and get an in-depth knowledge as the shop expertise is dwindling. Not to mention that many shops whom used to work on the 6.5 tend to remember all the old issues and are not up to date with the recent changes that make the 6.5 a lot better than its OE days. Also, planning to have either a spare vehicle, or renting, when the money-maker goes down for repairs is a good business model to follow.

If you do decide to go the 6.5 route, folks here will help you save a *lot* of money in repairs as I can affirm that they have helped me when I had decisions to make. In addition, my mechanic (whom still works on a lot of 6.5's) is actually very glad that I am able to do homework, help guide him with repairs, and give him knowledge of current parts supplies for the 6.5.


3500_6.5 said:
Yeah, whenever someone says they are getting 20+ mpg out of their diesel, chances are they are over exaggerating, can't calculate mpg correctly, or are just flat out lying.
Click to expand...

Hmmm . . . Guess that puts me in the 'Certified Fibbers' club then :D

With the 506 block, stock injectors, ATT, and HT tires, I got 17 - 19 around town and 20 - 21 on the highway. With the P-400, marine injectors, ATT, and HT tires, I am now getting 18.5 around town and 19.5 highway. Suspect the lower highway number with the P-400 is due to speed limits that were 65 mph when I had the 506 block and now they are 70 mph. Also, I am now doing the highway miles with a bike rack, so the drag is likely eating at least 1/2 mpg at 70 mph. Another possible factor is that there is more bio in the fuel than when I had the 506 block.

But in terms of overall mileage to expect in MN winters, even with a good system and a 3.73 rear, I'd expect mid to upper teens for highway mileage due to loss of fuel to heat the motor and extra drag from cooler driveline fluids.
 
Don't have much to add except welcome to TTS
and in my old 93 2wd at 55mph I got 25mpg from it. This was back in 95-96 time when diesel was DIESEL!
Also it cost $.99/gal too
 
Many sincere thanks to you all. I'm looking under $5000 and ideally around $3000. As for the appearance, I'm not concerned. I'm not looking for clients or customers. I buy real estate to fix or build new and sell. And I park in the back of the lot when meeting new investors.

I really do want a diesel, but from all of your advice, I'm leaning toward a 5.7 suburban. And due to my wife's school schedule and kid swapping, it has to have room for 2 car seats, my long legs, and a Great Dane. No way around that.

In another year or so, I'll be on here every other day trying to figure out the diesel truck I buy. And I may still buy a 6.5 Sub, in which case, I'll be on here telling all of you how right you were.
 
Just keep learning, and look for that good deal. I've never bought a brand new rig- I let others eat the depreciation $ for the Woohoo factor. I learned, any used rig,meet $1,000 in the repairs column in the first year of stuff you don't know about.

For whatever you go with there is a lot of diverse knowledge here.
 
I've had both. A 98 k1500 suburban with a vortec 350 and my current 95 k2500 6.5 suburban. Both are 4x4, automatic and 3.73 gears. The half ton gasser got 15 mpg pretty consistently. The 6.5 currently is usually in the 12-15 mpg range (this is mostly country road and small town driving with little highway driving). The gasser was a nice vehicle. I enjoyed driving and had no issues with it. Both are/were used as daily drivers. The only downside is that it couldn't haul much. If you plan to pull a trailer, the diesel is a no brainer. But if fuel mileage is the biggest concern, I would stick with the gas version. Even if the diesel does get better fuel mileage, gas (at least around here) is pretty much guaranteed to be a minimum of 30 cents cheaper per gallon, and not uncommon to be 50-60 cents cheaper.

Given the choice between a gas or diesel suburban, for me, I would still pick the diesel. But that's bc I like diesels. I like the sound, I like the smell, I like the torque when I need it and I like the uniqueness of the diesel suburban. Fuel mileage isn't a huge factor for me. I am a mechanic (or at least I was and still am on my own vehicles) and have had 6.5s for years, so I have no problem working on them. But diesels are inherently more expensive for everything. Fuel, fuel filters, oil (price and quantity), and most of the engine parts in general. And shops love to charge more to work on diesels bc for some reason diesels seem to be a mystery to most people. So even just filling up the tank and changing the oil when it's needed (and fuel filter on the diesel), your general maintenance will be more expensive with the diesel. I love my 6.5s and am all for them, I don't really have any issues with mine, and I think you could be satisfied with either a gas or diesel. But I think you will have better luck finding a solid running gas suburban than a diesel one. Generally, the diesels are neglected and require some money spent on them to get them where the gas version is usually already at on a similarly priced truck.

And just a few ironic fun facts for you. I have a suburban, it will require a second car seat in about a month, I had a Great Dane (passed away 2 years ago this coming January) that use to ride in the back of my suburban, and I also flip houses. But I have short legs. Really short legs lol.


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You will love the Burb. Consider looking for the next body style (GMT800) from 2000 - 2006 and the 3/4 ton (2500) with the 6.0 gas. Either the Burb or Yukon (must get the XL). Plenty of room for all. And chances are that you can park it in front of the house as the body lines are still appealing to today's consumers.

Kids will love it when you put down the middle row and put them back in the 'limo' position. Dog will love it that it gets to lie in the middle section and lick the kids as they are strapped in. Wife will love it as there is still plenty of room after the 3'rd row to stuff all the luggage and nobody gets cramped. You will love it as it can tow.

When it is time for the 6.5 Burb, it has all the same interior benefits as the GMT800 (IIRC except for side curtain air bags), but make *absolutely* sure the wife is on-board with the extra noise. Not everybody appreciates the diesel drone and clatter (when it is cold) of an IDI.
 
We can help you with the McDonald's cheeseburger -Billions made GM 350 GM engines. Cheap, stupid simple, and easily warmed up. If I had to go gas it would be the 6.0 or the 454 as GPM *cough* MPG doesn't matter to me as much as power and towing.
 
I must be in the group of fibbers, if mine dont clear 15 mpg empty at all times, its time for a change. :) my 95 GMC 5spd 2wd is by far my best mpg rig, it will get 21.5 empty, and will get as high as 14.8 mpg with the gooseneck on. (had a good tailwind across wyoming) and averages 12 mpg with the trailer.

Unless there is a bad headwind involved, I have never dropped below 10 mpg towing heavy with any of my 5 speed 6.5Ls

That said, if you are shopping for a 4wd automatic, dont expect that great of mpg.

As far as your use for it, I too would reluctantly go with a gasser. The wife and kids and the winter driving are the main reason. IMO a 6.5L needs to be a one driver rig so you can keep an eye on it.

That said, I love the 6.5L and will take it over any gasser. This forum is a valuable tool that will help a guy affordably own and operate a 6.5L.

If you are tight for cash, I think I would recommend a half ton gas suburban or 4 door tahoe for the wife in the GMT400 body style, and then when you can swing it, buy a 6.5L for the business, IDK what your exact needs are, but maybe a reg. cab 6.5L 5 speed. That would at least get some mpg, and fixed up a little, everyone allways loves a clean Reg. cab. :)

Good luck!
 
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