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Diesel vs gas


keyman
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I need to buy a new hauler, trying to decide gas or diesel. Wondering about cost/up keep/fuel etc. Thought I wanted a gas motor but just drove a Penske diesel half way across country and kinda like the low rpm grunt though it gulped down $700 of fuel. Any input would be appreciated.

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How big are you looking to go? In anything over a 3/4 ton pickup your choices are going to be limited almost exclusively to diesel. How heavy is your trailer?

 

About a year ago I switched out of a gas daily driver (a '99 GMC Yukon with the 5.7L and a towing package) to a roughly equivalent diesel ('94 6.5L C2500 Suburban) with LESS horsepower (same 3:73 gears btw) because the extra 100 ft/lbs of torque the diesel offers, plus the increase in gas mileage (gained about 5mpg) plus the heavier-duty nature of the diesel makes life a lot easier. I always kinda though guys who drove diesels all the time where silly due to the higher cost of parts and oil but the diesel is much heavier so it breaks less and the oil is more expensive ($25 Valvoline oil and filter on the gas truck versus $60 Rotella T, Lucas Additive and oil/fuel filters) on the diesel but it's 5K miles instead of 3K. If you are going to be using the truck a lot more daily than for towing and are looking at a Duramax/6.0L Ford/24V Cummins truck then the reduction in fuel mileage of unloaded diesel vs. unloaded gas truck may not be worth it but while towing the diesel will typically get higher mileage than an equivalent gas truck. I've been so happy with the switch that I am now looking at eventually converting my shop truck (a '68 C10) from a 283 gaser to a 6.2L diesel not for the extra power (the 6.2L is a dog) but for the extra gas mileage!

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I bought my first diesel f250 with a 7.3 in 2000 and I haven't had anything since. Although when I bout it diesel was 10 cents cheaper than gas and about 80 to 90 cents a gallon. Also I got about 5 more miles per gallon before they added all the environmental additives but all I've done is replace an alt and and ac compressor in the last 13 years and now getting close to 400,000 miles. Towing I can't even tell the race car is back there. The oil and fuel are a little more expensive. But I've been changing mine at 7500- 10000 miles since I had it with no problems. I hear the 6.0 you should stay away from but both dodge and the new ford 6.7. I hear good things about. I get people wanting to buy mine all the time after they hear it has a 7.3 in it. For towing diesel all the way for me.

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Diesel definately. However dont expect the end of year to show a significant gain. Gas engines are cheaper and maintenance is also cheaper along with fuel prices. But they require more maint more often. Diesels are expensive to buy but get better mileage, towing or not. Fuel prices are higher. Maintenance is costly but not as frequent. Some people think its a wash. Ive got a now 11 year old Dodge with a Cummins and even though its old and ugly, it gets 18+ mpg daily driving and 11-12 towing a 38' fifth wheel thats over 12 feet tall. I cant complain.

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diesel for MOST cases. I probably would have gone either way until owning my F250 - 9 -11 mpg no matter what I pull!

 

If the vehicle will also be used for short runs (like a grocery getter) expect maint to be a bit higher though. Especially with the exhaust filter stuff on em. Diesels LOVE lots of warmup and hiway miles! short cold miles are BRUTAL.

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I HAVE HAD THREE FORD DIESEL AND I HAVE HAD ONE DODGE AND I PERFER THE DODGE DIESEL. I`M A AUCTIONEER AT ALL THE DEALER AUTO AUCTIONS HERE IN SA AND ONE THING YOU MAY WANT TO CONSIDER IS RESALE VALUE TO. FORDS 7.3 ALWAYS BRING A LOT OF MONEY WHEN YOUR READY TO SELL I DONT CARE WHAT THE MILES ARE BEST MOTOR EVER!!! BUT JUST CANT FIND THEM ANYMORE DONT KNOW WHY THEY QUIT BUILDING THEM AND TO BE HONEST JUST ABOUT ANY DIESEL HAS A BETTER RESALE THEN ANY GAS MOTOR. AND YES IT COST TO MAINTAIN IT MORE BUT YOU JUST GET ALOT MORE OUT OF DIESEL! GREAT FOR PULLING!!

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Thanks guys, I will only be using it for towing (racing and hauling safes) so I,m convinced. I prefer a GMC or Chevy, any good or bad motors?

Gm isnt known for making any good diesels that I know of, maybe somone has some personal experiance with them that liked it. Montgomery is right about the ford 7.3 being king but I think the new ones are good too. Also I hear great things about dodge. I think thier cummins engines and I was talking to someone that had a new one outside of his truck while it was idleing and it was so quiet I had to ask if it was a diesel!

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Thanks guys, I will only be using it for towing (racing and hauling safes) so I,m convinced. I prefer a GMC or Chevy, any good or bad motors?

Gm isnt known for making any good diesels that I know of, maybe somone has some personal experiance with them that liked it. Montgomery is right about the ford 7.3 being king but I think the new ones are good too. Also I hear great things about dodge. I think thier cummins engines and I was talking to someone that had a new one outside of his truck while it was idleing and it was so quiet I had to ask if it was a diesel!

I know the Fords are good but I just don't feel comfy in them. Can't afford a new one looking for a good deal on one 96-02. Anybody got one?

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If you're a GM guy it all depends on price range.

 

If you want something cheap but don't mind spending some money on it slowly after purchase the GMT 400 (88-99) Pickups are a great choice. They ran a 6.5L that is a Detroit Diesel design and while they get a bad rep as long as you attend to some design issue they are stone cold reliable and get astounding gas mileage. Like I'd mentioned I run a 6.5L Turbo Diesel in my '94 Suburban that was an original "no emissions" truck and get roughly 16-18mpg average around town and 14ish towing, the highway mileage is over 20 unladen. Mine has 240k miles on it, when I bought it as an old-neglected farm truck it obviously hadn't led an easy life so I spent a little bit time cleaning it up and then did a few upgrades. These trucks have known cooling system issues so I cleaned the radiator fins, put a higher volume water pump in, put a AC Delco thermostat in, sourced a high-output thermostatic fan clutch and am running a later model Duramax fan. I am also running a relocation kit to keep my injector driver cooler along with two-stroke oil on fillups to keep the injection pump alive with modern diesel. I have a real light chip on the truck and while it's not "fast" it'll more than put me back in the seat, will tow anything I ask it to and STILL gets good mileage.

 

If you've got more money the Duramax is a great if not slightly less popular (among the big 3) modern choice. The early Duramax's up until mid '04 had cylinder head and injector issues so I'd go '05 or newer unless the heads and injectors have been upgraded to later or aftermarket parts. The '05 and up Duramax trucks are as indestructible as anything on the market, in-fact I've got a family members on our lot right now on consignment with 38xK miles on it that runs like a top and we've had them with as high as 450K miles. The Duramax trucks from '05 on can be made to tow as well, make as much power as and get better gas mileage than the late model Ford/Cummins trucks and the remainder of the vehicle is still GM stuff so it's easy to service.

 

If you're considering a 6.5L or Duramax truck thedieselplace.com is a great source for buyers guides and information related to the long-term viability of these trucks. Keep in mind GM has been building the 6.5L engine since '88 and it is still in production today as a military and industrial motor (H1 Hummers run 6.5Ls) so it's no junker and the Duramax has been in steady production since '99 so it's pretty well scienced out as well.

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The Gm duramax is an OK engine, just not to effecient. They usually need a programmer and some other upgrades.

Im a cummins fan but the new cummins isnt worth much IMO. It has decent power but crappy mileage. However, unlike new FORD and Chevys, it doesnt require DPF fluid. But im sure its coming.

Each make has its own issues, my advice, decide what you like and go from there. Sounds like there are a lot of guys with experience on here to help you steer clear of the problem children.

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Good stuff James!

 

On the 6.5 once you address the cooling - the castings are real sweet. Without address - the head likes to stress crack where the precombustion chamber, head surface and cylinder wall meet up - even when coolant never goes over 225. I also recommend a GOOD harmonic balancer on it - with high miles they tend to crack the crank at the #1 main rear radius due to accessory load stresses.

The Duramax had not been produced by my retirement so I can't form an opinion based on service issues to compare.

My opinion is ANY diesel should be 125% on the cooling system - no margin for neglect - they just have harsher heat cycles which makes for brutal expansion cycles of the parts. Maintaining a constant temp becomes critical - your system should "ride" the thermostat (in other words have the ability to cool below the thermostat's value with the thermostat fully controlling temp)!

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Good stuff James!

 

On the 6.5 once you address the cooling - the castings are real sweet. Without address - the head likes to stress crack where the precombustion chamber, head surface and cylinder wall meet up - even when coolant never goes over 225. I also recommend a GOOD harmonic balancer on it - with high miles they tend to crack the crank at the #1 main rear radius due to accessory load stresses.

The Duramax had not been produced by my retirement so I can't form an opinion based on service issues to compare.

My opinion is ANY diesel should be 125% on the cooling system - no margin for neglect - they just have harsher heat cycles which makes for brutal expansion cycles of the parts. Maintaining a constant temp becomes critical - your system should "ride" the thermostat (in other words have the ability to cool below the thermostat's value with the thermostat fully controlling temp)!

 

Thanks you and thanks for reminding me; I put a lifetime warranty balancer and crankshaft pulley on mine (separate pieces and both rubber isolated) that I check with just about every fill-up. The final benefit to the old 6.5L is that they run a 4L80E which is only a 4-speed with lockup converter but is nearly the most bullet-proof transmission ever created by man or otherwise. The five speed trucks run a modifed NV4500 5-speed that has a PTO output if needed.

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  • 8 years later...

I know I'm responding to an older post, but this is the eternal question so I will play. This is the argument like others that play out among gearheads every day. Ford vs. Chevy. Dirt vs. Asphalt, etc.

A little background.....I'm a diesel mechanic by trade and despite what academia or "environmentalists" may think about that, I love what I do. At work, I work on everything from semi tractors to heavy earth moving equipment. GOD has blessed me with a lucrative means to make a living and support my family. I'm a kid that still plays with trucks, but just on a larger scale. Enough about that.

The irony is the fact that BOTH of my race car haulers are gasoline powered. I use my crew cab to haul to local tracks and the motorhome  for longer ventures. I'm in California, but I know most of you are from Texas. GOD willing, I would love to make it out there to race, hopefully before the end of this season. I picked up the crew cab from the truck dealer I worked at the time. It was a trade in that needed some transfer case work, so instead of doing a recon, they decided they were gonna wholesale it, so I picked it up. When I was looking for a motorhome, a diesel wasn't really an option in my price range. I picked it up used with only 18K miles. The guy I bought it from couldn't get it to pass smog, so I took it off his hands. Both of them are powered by the latest big block, the GM 8.1L.  I would love to have a diesel, but both of these machines kinda came across at the right price at the right time. That being said, I have no regrets and I will tell you why, besides the fact that they are both paid for. No loan payments!

I would say that if you can afford it, go ahead and spring for the diesel. If you can afford a DMAX, the 06-07 VIN D LBZ is the best pre-emission engine made. It starts @ 650ftlbs of torque, but easily responds well to minor tweaking. If a pre-2000 truck is more in your price range, spring for the 1998-2000 Classic with the 6.5 VIN F engine. The later ones have dual thermostats which takes care of some of the earlier overheating issues. ANY truck you buy whether gas or diesel should have the hoses replaced along with a new cap. Use the best parts you can get; Continental, Gates etc. Try to get their fleet grade stuff if you can. As said in an earlier post, use an injector driver relocation kit to keep it cool. Use a cetane booster/ fuel conditioner from either Stanadyne or Motorcraft to keep that injection pump alive when running ULSD.

In my opinion, gas engines have come a long way. Although unheard of 20 years ago. It is not uncommon to see the LS engine go 200-300K without using a lick of oil. At the truck dealer I worked at, we had an account with Bragg Crane. They had a huge fleet of trucks using the LS engine. Many had well over 200K. These trucks were not babied by their drivers by any means. If you kept clean oil in them, they would run forever. Engine oil technology with synthetic becoming more affordable and mainstream has extended gasoline engine life significantly. I work with a fleet where many of our Ford F250s have the 6.2L engine in them; many over 200K miles, no valvetrain noise. We have a few V10s with over 300K on them. Our linemen cover from Southern California to Nevada and Utah. They would take these trucks without thinking twice.

In conclusion, it is a personal and financial decision you have to make. The DMAX is little more expensive to purchase and maintain, but  overall a good engine. The 6.0 is reliable but may spin hard pulling a grade. It may take some mods(intake, exhaust, camshaft, programming) to make it better. The 8.1L is good, but severely detuned from the factory. Oftentimes, just  taking off the torque management makes a big difference.You can do mods (intake, exhaust, camshaft, programming) to approach diesel torque numbers but fuel mileage will still be better in those early DMAX engines. Later DMAX engines with aftertreatment (DPF & DEF) experience less MPG and less longevity.

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  NEVER OWNED A DIESEL .  never needed one  BUT MY BROTHERS have owned them all .. one of my brothers just got rid of his 2 year old dodge better milage but nothing but trouble always something wrong with it .he had to replace the front springs  drive shaft  somethings else in the motor  and always vibrations  .he love the power it had but 150.000 miles he had enough .. he has a bad back  and fords seats hurt him  other wise he would buy one .. so he now just bought a gmc  .loves the truck  but feels like its lacking in power and fuel mileage wasn't as good as the dodge ..... my other brother owned a early gm  .but went to ford when they had that junk motor and trans 20 years ago  .but has never owned anything else sense .. all  ford ..  .. MAINLY LOOKS LIKE  what are you going to use it for i think ..as for milage  unloaded  it gets about the same mileage as my little v6  i have in my dakota .. . but you want power  mileage will drop 

Edited by HiTech
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  • 3 weeks later...

every one will have their own bias. I'm a dodge/ram guy.  but I know people that have had issues with all manufacturers.  my best suggestion is that people go drive them all and see which one they prefer and can enjoy.  because they all have their issues.  also gas vs diesel will always be a debate.  all depends on your needs.  the weekend puller that commutes with their truck daily to an office and home usually just needs a gas engine.  but if you can live with the gas mileage of the diesel it is nice to have when needed.

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