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General/Gas vs. Diesel:

Breggin, Dave wrote:

> Differences between the Diesel and Gas engines:

> Diesel is cooler (adds to life expentancy)

> Torque peak is at lower rpm on diesel (1700 - 1800 vs.
> 2400 for gas). This allows the engine to start heavy
> loads better from a stop (i.e. the Big Rigs), and it
> allows full engine power at a lower ground speed (good
> for off-road control).

> Dave Breggin
> '95 Diesel Wagon

More differences between gas and diesel engines:

  • Gas engines are much lighter putting less weight on the front end,
  • gas engines are quieter
  • gas is much easier to find in some areas (mexico and canada/Alaska trip)
  • gas hummers don't puke foam all over when filling them
  • I have a gas engine
  • gas engines are much easier to get parts for and cheaper to rebuild

OK, OK...if I were to buy another Hummer I would probably buy a turbo diesel. I guess I just wanted to help show that no matter how you look at this question there is no right answer, it is all personal preference. That and I felt like arguing tonite (sorry Dave).


Diesel + / Gas -

  • Diesels have a larger main tank, 25 vs 23.
  • Diesels are much more effcient than a gas motor at idle and at low power. A diesel uses almost an order of magnitude less fuel at idle than a comparable gas engine. At 20% power output, they consume about 35% of the fuel a gas motor does. At 100%, use about 85%.
  • Diesel is extrememly hard to ignite (safety).
  • Diesel is denser (~7lbs/gal) so you get more lbs of fuel per gallon (see above).
  • Torque available at lower rpm. Better for slow steep climbs.
  • Inherently strong engine construction.
  • "Waterproof".
  • No tune-ups.

Diesel - / Gas +

  • Fuel availability.
  • Gas-cleaner fuel, does not stink out from the exhaust, no fuel filter problems.
  • Gas-much quieter.
  • Gas-overall more reliable.
  • Gas-slightly better gas mileage?
  • Usually less hp.
  • Gas-more even power curve to higher rpm.
  • Hates water. Grows algae. "gels" at lower temps.
  • Gas engines have better engine braking.
  • Diesels generally run hotter. Built with higher tolerances.

Turbo stuff -

  • If you don't need the power, don't get it.
  • They add stress to the motor. Increase piston and ring wear due to higher filling and firing pressures.
  • Many more parts to break. Turbine shafts touchy to lubricate.
  • Turbos run very hot, not good for deep water.
  • They seem to be quiter than non-turbo.


I had a gas wagon for over two years and now I have a Turbo diesel wagon.

>> Gas-slightly better gas mileage?

Definitly the Diesels have better fuel mileage. The gas never did better then 11 mpg while the unbroken diesel got 13.5 mpg. on the road. Off the road the diesel gets 2 to 3 times better fuel milage then the gas.

> Gas engines have better engine braking.

The gas engine has way more engine braking than the diesel. Its because of the way they operate. A diesel's intake manifold is always wide open. The engine power is controlled by the fuel to the injectors. A gas engine has a throttle plate that closes off the air intake when slowing down creating an intense vacuum that the pistons have to work against, thus the braking effect.

> Diesels generally run hotter. Built with higher tolerances.

Diesels run cooler then comparable gas engines. A diesel is more efficient and gives off less heat. The temperature of the Hummer gas and diesel is set by the thermostat. The gas engine under the hood gives off considerably more heat. The exhaust on the diesel isn't nearly as hot as an exhaust on a diesel.

Dave said:

>I should have included that with the gas engine torque peak at a higher RPM, you get better performance on-highway at the higher speeds.<

The only problem is that as you go faster in an unaerodynamic Hummer the wind resistance increases and wipes out all that performance.

My first truck was a gas truck, and I am a die hard chevy small block gas engine person, this is why I bought it. There is hardly any difference between the off road performance of a gas vs. diesel truck. After I bought a gas truck I went to the AMG test track and drove one of their diesel trucks through all of their obstacles. What I found is that each engine has it's own distinct feel. Why did I get a gas truck? Because I know I can get fuel anywhere. If I'm out on the trail and somehow run out of gas the probability of a diesel truck coming along is very remote. The 350 Chevy small block is the most common engine ever built and can be repaired almost anywhere in the country. If the engine doesn't last as long as a diesel it can be replaced dirt cheap. There are more add on parts made for this engine than any other engine in existence. Its quieter, has no smell and starts up with no problem in the coldest weather. The gas truck can be sound insulated very easily. The fuel injection system automatically adjusts itself for the correct mixture at any altitude. A gas engine because of its design will allow engine braking. The only thing I can't do is ford to a 30" depth. The starter on a gas truck is not watertight and will only allow a 24" ford. Don't forget, just about all other 4wd's made are gas powered. The 95's have 23 gal gas tanks which are small considering that you will get 8 to 11 mpg. Off the road while in Colorado I got about 4 mpg. All the 96 trucks have an additional 17 gallon tank.

I now have a 96 Turbo diesel wagon and I have to eat my words. It's now my opinion that a 7000 lb truck really needs a diesel. The major differences are more torque at low rpm's. I get 11.5 to 13.5 mpg. The truck hardly uses fuel when off the road. It just idles along putting out all kinds of torque at 1800 rpm. The TD is much better on the road because of it's increased power. It turns out that diesel fuel is pretty easy to find. With all the diesel pickup's and farm equipment pumps are available everywhere. The diesel doesn't smell either. Because of pollution requirements new diesels burn clean. It is a little harder to start when it's cold and it was a lot harder to sound insulate then the gas. Of course the 97's are much better sound insulated right from the factory.

As you are aware, I did the same thing. I had a 1995 Gas Wagon, and went to a 1997.5 Turbo Diesel. I was always a die-hard gas man (no pun intended), but I changed my mind the first time I drove a Turbo Diesel. Like night and day. I never went wrong with the gas engine, but the Turbo Diesel is better. Joe Cama

I had a gas truck for over 2 years and had no engine problems at all. After looking at all the options the most practical thing to do was to install a Whipple supercharger on the existing engine. Since the existing engine is a 4 bolt main marine engine it will easily take the extra stress of the supercharger. The reason I favor the supercharger is that it offered the most torque and horsepower at the lowest RPM. Most gas engines by design develop torque and horsepower at higher RPM where we don't want it. While it would be great to have a nice long stroke big block, it seemed to me to be a real major project that would end up costing a bunch and keeping my truck out of service in pieces for quite awhile. The Whipple installs without a major hassle and doesn't require you to risk bastardizing your truck. I drove a gas whipple supercharged truck and it was quick. It went 0 to 60 in about 13.5 seconds and drove around in traffic like a sports car. It does require that you burn hi octane gas. If you take it easy it will get similar milage to the stock engine. Last I checked the Whipple cost 5000 and about 1800 to have installed.

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