I will be purchasing a used Chevrolet one ton soon. year range will be
between 1995 and 2000. I really don't care for the 454 engine as they
are gas hogs. That leaves the 350 vortec and the 6.5 liter diesel. I
am very familiar with the 350 and know their limitations, however their
gas mileage is better that the 454. I am under the impression that the
6.5 will get mileage in the low 20's and have a lot more muscle than the
350. Should I go with the diesel? Is the cost of maintenance and
upkeep for the diesel not practical compared to the 350? I wont be
pulling heavy loads just carrying heavy loads on occasion. This vehicle
will also be used for daily driving.
How about some feedback
When buying a one-ton truck the thing that saps your mileage is that they
generally have a very high numerical rear end, usually 4.10:1 - great for
moving heavy loads but bad for highway mileage. If you are looking for a
larger capacity truck that will only occasionally haul heavy loads and will
get its greatest use commuting, then I suggest you look into a 3/4-ton truck
with a 3.73:1 rear axle.
As for the 6.5L turbo diesel compared to the 350 gasser, the cost of
maintenance is about the same, but the 6.5 has two issues that you should
investigate before you buy a vehicle with that motor. The first is in '97
or '98 GM moved to a higher capacity water pump with dual thermostats and a
crossover. The earlier versions had a problem with burn-through of the head
gasket in the rear cylinders when the motor was used for heavy hauling or
towing and the new pump and thermostat set-up all but cured this issue. If
you are getting an earlier ('94-'97) truck with this motor, see if the water
pump and thermostats were upgraded to the later design.
The second issue is the Fuel Solenoid Driver (FSD) mounted on the front of
the fuel injection pump. This little black box generates a lot of heat
which (in theory) is supposed to transfer the heat to the fuel pump body and
be cooled by the fuel flow. Unfortunately, this may have worked well on the
test bench, but when in a truck's engine bay with little or no airflow
around the FI pump, the FSD has a nasty habit of overheating and frying. If
you don't catch it quickly enough, the heat will also fry the optical sensor
inside the FI pump and then the entire pump will need to be replaced at a
cost of $1800.00 or more. Plus the added heat from the FSD also thins out
the diesel fuel and that's not good for pump lubrication.
The cure for this is an FSD Cooler (you can search for this on the net and
get a better explanation that I can provide) which is nothing more than a
finned heat sink that the FSD is mounted on away from the FI pump. Any heat
the FSD generates is bled off into the atmosphere instead of the pump body
and everything works fine. I suggest getting a new FSD at the same time as
the cooler instead of trying to take the old one off the pump - which is a
tremendous PITA because you have to remove the intake manifold and all the
plumbing to even get at it. You can even buy an extended harness to move
the FSD even further away from the motor for better cooling, but I used the
recommended mounting position and no extension with no problems and my '95
6.5L gave me great service.
Cheers - Jonathan
I would, however I have dump bed that i will be putting on it and the
frame width on the one ton is the correct size. I think the frame on
the 3/4 ton is wider by several inches.
thanks for the feedback
Now I understand.
I personally wouldnt buy a diesel, their too high maintenance and of course
its good they will run a million miles most the time, but just to run around
town I would stick with a gas engine.
From personal experiences (after owning gassers for over three decades), I
would tend to disagree with diesels being too high maintenance, that is,
compared to gassers: no spark plugs, no plug wires, no distributor, no
coil/ignition module, no O2 sensor, no lean/rich adjustments, no vapor lock,
Just like most gassers, change the oil/oil filter (religiously), air and
fuel filters as needed, and follow manufacturer's recommended maintenance
Adding to Jonathan's list: the oil lines to/from the oil cooler, and the
heater hose from water pump/thermostat housing.
Hi maint. ????? !!!!
I have 252,000 on my cummins & it's never been looked at...just filters &
oil. My friend had a 6.5..it was no power house for sure, but it ran great &
got the best mileage I've ever heard of(32+).
Diesels are great,but the hi price of the engine and hi fuel prices force a
person to keep the vehicle long enough to re coop the $$....as I have-15
I disagree, especially since we are talking about diesels here. Keeping the
RPM's in the "sweet zone" for a diesel means keeping them low where the
engine is most efficient, which means a 3.73 will be just fine for the
application the original poster mentioned (mostly commuting, occasional
hauling). The most efficient RPM for a gasser is much higher so it will not
suffer as much from a higher ratio rear end. My 3/4-ton Chevy is rated at
15K+ lbs on a fifth wheel hitch with a 3.73 rear end, but still gets 21+mpg
empty on the highway. If I had 4.10's in the rear I might gain 1000+ lbs
towing a fiver (which I don't need), but running empty on the highway at the
same speed would keep my RPM's higher than my motor likes to cruise at and
would sap a few MPG (which I don't need either, especially at $2.30/gal for
diesel). Of course I could run slower, but the speed limit is still 70mph
regardless. When commuting with a larger truck, you're not looking to
launch like a Corvette from every streetlight, so a 3.73 rear would be just
fine and help bump up the mileage around town with the diesel - I get just
over 18 when I commute with mine. My old 6.5L diesel with 3.73's got 17
commuting and 22+ highway empty religiously.
I don't know how heavy a load the OP will be hauling or how often, but since
the 6.5L turbo diesel generally put out around 200HP and 400 ft-lbs of
torque in it's final version, then it'll be up to him to decide if hauling
is more important than commuting mileage.
Cheers - Jonathan
I tend to agree somewhat with this on a diesel engine but it depends
on load too, If you plan to haul heavy with a 6.5 I would still go
with a 4.10 because it would give you more towing power and you would
still have about a 2000 RPM cruise at 60 mph or so in OD (better
pulling power in OD) and the 6.5 with its much higher compression and
prechambers has a wider useful RPM range and rev a bit freer than a
Dmax or a Cummins. With those engine I would go with a 3.73 unless
regularly towing 14k or more. If you plan to run oversize rubber too,
go for deeper gear to offset power loss from bigger tires too.
Original poster stated he won't be pulling heavy loads, just carrying heavy
loads on occasion. With that, the 3.73 should be fine. 63 mph/1800 rpm
(max torque for 6.5TD) should give him the optimum mileage performance (22
mpg on our 4x4 2-Dr Tahoe).
I just bought a 94 GMC 1 ton crew 4x4 with the 6.5. Just sold the same exact
truck but with a 350 gas motor. Mileage is much improved from the gas truck.
Getting 19-21 mpg empty. The gasser got 12-14 mpg empty. The warranty on
the inj. pumps is 11 years or 193,000 km. They had numerous troubles with
inj. pumps and FSDs. Also some lift pump troubles from what I've heard. All
that said, I much prefer the diesel over the gas for moving a heavy truck
like a 1 ton crew.
Merc(converted Ford man)
94 GMC 1 ton crew 4wd
Here is the cooling system upgrade for older 6.5 diesels. Have not had any
overheating issues with my 94 with the old cooling system though, even when
towing 8000 lbs.
"gas mileage is better that the 454. I am under the impression that
6.5 will get mileage in the low 20's and have a lot more muscle than
I wouldn't necessarily jump the gun on that.
My stealership owner/mechanic friend had (and quickly sold--in a good
way) a K3500 dually XCab 6.5L/5-speed/manual t-case, 98 model.
He got 14mpg's no matter what with that truck.
He also had (end result as above, too) a 4x4 94 model 6.5L "heavy
half-ton" truck (K1500) that got 18 tops cruising to and from Florida,
doing 80, but not awesome as one thinks a diesel would do.
He currently drives for himself a 2000 F350 CC w/PSD/auto/2wd.
13mpg's. He does use jet fuel mix, but deinitely NOT 20+mpg's.
Don't fall for the semi-myth of VASTLY better mpg's from a diesel in
such a big truck. My Stepdad's 3/4-ton 2000 Xcab/long bed Chevy with
big block gets 14+ on the highway.
To boot, a 350 in that big of a truck will struggle a bit more compared
to the 454....therefore any wished for mileage efficiency has gone
Actually, the mileage you quote on the vehicles you list isn't totally
unexpected. The '98 K3500 extended cab dually is an extremely heavy truck
and I'd wager that 14mpg with the 6.5L would be about 5mpg better than you
get with an identical truck with the 454 gasser.
The same for the '94 K1500 (which has the earliest, least powerful version
of the 6.5). Speaking from personal experience, if he had slowed down to
72mph on his trip to Florida he most probably would have gotten 21+mpg. At
80mph the 6.5L in that 4x4 was pretty far outside the sweet spot in the RPM
range and anything will suck gas at 80mph with the aerodynamics that a
pick-up has. He still did better than what the same truck would have done
with either the 350 or 454 of that year regardless.
As for the Ford F350, this is a motor that is not known for it's fuel
efficiency at all, and 13mpg is exactly what I would expect for that truck.
On the other hand, my current Silverado 2500HD 2wd crew cab with the 6.6L
Duramax and Allison tranny with 3.73 rear end will get me over 21+mpg on the
highway at 72mph empty, and 18.5mpg religiously in combined commuting-type
driving. Not bad for a truck that weighs like a tank.
Cheers - Jonathan
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