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Stupid Question: How to drive a 12v

8716 Views 38 Replies 16 Participants Last post by  country_hick, 
alanack6795
Okay, ive been around trucks my whole life but last march i decided to sell my stupid VW and my s10 and i bought my beloved 94 12v.

Just wondering if im doing this all right :confused013:

I run all fleetguard filters with Rottela T6 change every 7k

Fuel filters every other oil change
Should i be using some sort of additive ( like fuel injector cleaner every so often)

I always plug it in when its real cold and i always let it warm up until the temp comes up to 140

Now what is the "Right" way to drive these trucks in order to get decent mpg and let the engine last long.

Some tell me me to mat it and drive it hard because "thats the way diesels like it"

Others tell me to drive normaly or grandma it for best mpgs. :S:

I only get 17-18 combined driving with 245/75/r16 and 3.5 gears automatic 4x4
Please dont make fun of me, im just trying to do things right

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country_hick
alanack6795 said:
O
I run all fleetguard filters with Rottela T6 change every 7k

Fuel filters every other oil change
Should i be using some sort of additive ( like fuel injector cleaner every so often)

I always plug it in when its real cold and i always let it warm up until the temp comes up to 140

Now what is the "Right" way to drive these trucks in order to get decent mpg and let the engine last long.

Some tell me me to mat it and drive it hard because "thats the way diesels like it"

Others tell me to drive normaly or grandma it for best mpgs. :S:

I only get 17-18 combined driving with 245/75/r16 and 3.5 gears automatic 4x4
Please dont make fun of me, im just trying to do things right
Click to expand...
Prolonged idling is generally considered not to be good for these trucks. The idle speed is to low. If you could get the idle up to about 1,500 rpm it would be a real improvement. Although this truck will not see winter roads my last (now rusted away) diesel did. All I really did was start it and get oil pressure up where it belongs. I might use high idle for a minute or so and then take off. I noticed on this truck I need to give some throttle for a minute or so in cold weather so the truck will idle above 500 rpm. When it warms up enough to idle well I take off. You may find you want to idle in neutral to refill the tc if you hesitate at first instead of taking off normally.

I would install a fuel pressure gauge (one that says oil pressure will work if you do not tell it that is not oil it is checking). Make sure you install something to smooth out the fuel pulses or it can destroy the gauge. That way you can see when fuel pressure drops and change the filter when it is needed instead of by mileage. You might go 100,000 miles and not plug up your fuel filter or it could get clogged from bad fuel in under 1,000 miles.

Additives except for anti-gel (in winter for summer fuel) are generally not needed.

My truck is a dually. I push around 2 more tires than you do.

I drove for good acceleration. I was accelerating at 2,000 rpm perhaps even 2,100. Driving locally I got a 16.25 mpg tank. I was unhappy with that number.

I watched my tach. I kept it at 1,250 to 1,500 rpm while accelerating. For 3 tanks I got 19.+ mpg.

That tells me that accelerating slowly saves fuel at least on a stock automatic.

Driving the truck home about 1,850 miles I got 23.5 and 26 mpg driving 1,500 rpm and 54 mph. I did 1,600 rpm once and get 1-2 less mpg. Close to home I pushed the speedometer up to 70 and about 1,900 rpm. I got about 18 mpg.

That told me that driving slower saved more than enough money to pay for a hotel room if it took an extra day of driving slower to get home.

One thing that will help mpg is a better torque converter. The stock one is about 65% efficient. A good aftermarket version is about 90% efficient. I was told that can be good for 1-3 mpg alone. Getting a tc with a stall speed of about 1,700 to 1,900 will also help you not to accelerate uselessly at 2,100 rpm and barely move forward.

Diesels like to run warm. However, whatever they like to do they drink more fuel when you are at higher rpms ( at least empty as a heavy load can change things).
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country_hick said:
Prolonged idling is generally considered not to be good for these trucks. The idle speed is to low. If you could get the idle up to about 1,500 rpm it would be a real improvement. Although this truck will not see winter roads my last (now rusted away) diesel did. All I really did was start it and get oil pressure up where it belongs. I might use high idle for a minute or so and then take off. I noticed on this truck I need to give some throttle for a minute or so in cold weather so the truck will idle above 500 rpm. When it warms up enough to idle well I take off. You may find you want to idle in neutral to refill the tc if you hesitate at first instead of taking off normally.

I would install a fuel pressure gauge (one that says oil pressure will work if you do not tell it that is not oil it is checking). Make sure you install something to smooth out the fuel pulses or it can destroy the gauge. That way you can see when fuel pressure drops and change the filter when it is needed instead of by mileage. You might go 100,000 miles and not plug up your fuel filter or it could get clogged from bad fuel in under 1,000 miles.

Additives except for anti-gel (in winter for summer fuel) are generally not needed.

My truck is a dually. I push around 2 more tires than you do.

I drove for good acceleration. I was accelerating at 2,000 rpm perhaps even 2,100. Driving locally I got a 16.25 mpg tank. I was unhappy with that number.

I watched my tach. I kept it at 1,250 to 1,500 rpm while accelerating. For 3 tanks I got 19.+ mpg.

That tells me that accelerating slowly saves fuel at least on a stock automatic.

Driving the truck home about 1,850 miles I got 23.5 and 26 mpg driving 1,500 rpm and 54 mph. I did 1,600 rpm once and get 1-2 less mpg. Close to home I pushed the speedometer up to 70 and about 1,900 rpm. I got about 18 mpg.

That told me that driving slower saved more than enough money to pay for a hotel room if it took an extra day of driving slower to get home.

One thing that will help mpg is a better torque converter. The stock one is about 65% efficient. A good aftermarket version is about 90% efficient. I was told that can be good for 1-3 mpg alone. Getting a tc with a stall speed of about 1,700 to 1,900 will also help you not to accelerate uselessly at 2,100 rpm and barely move forward.

Diesels like to run warm. However, whatever they like to do they drink more fuel when you are at higher rpms ( at least empty as a heavy load can change things).
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Excellent answer, bud.
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i always let it warm up until the temp comes up to 140
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You're actually hurting the engine and wasting fuel at the same time.
Wait for the oil pressure to come up then start driving keeping the rpm under 2000 till the temp needle starts to move.
Having the timing bumped up to 15-16 will give you better mpg and power.
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alanack6795
Im not really concerned about power, Driver a 7000 pound vehicle over the speed limit just puts other motorists at risk. Being a volunteer fire fighter i've seen enough bad wrecks. That being said i see no reason to give myself the temptation to drive faster than i should. Shes staying stock

Also i noticed i got better gas mileage when i let it warm up

I was looking to get a full set of gauges soon, not really sure what kind couldnt deside between autometer or isspro

How many more mpgs does advancing the pump timing give me whereabouts
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Bumping the timing up gave me about 2 mpg more.
Just because you have more power it doesn't mean you have to use it.

I don't see how you could get better mileage warming it up, fuel is wasted in the warmup period.
Also what happens with extended idle warmups on cold diesel engines is incomplete combustion in the cylinders.
Unburnt fuel washes lubricating oil off the cylinder walls causing rapid wear.
Unburnt fuel also gets past the rings and contaminates the motor oil.
This is called wash down. I can often tell a diesel engine that's been cold idled a lot just by sniffing the dipstick, smells like diesel.
It's the nature of the beast, diesel engines just don't warm up well idling.
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illflem said:
Bumping the timing up gave me about 2 mpg more.
Just because you have more power it doesn't mean you have to use it.

I don't see how you could get better mileage warming it up, fuel is wasted in the warmup period.
Also what happens with extended idle warmups on cold diesel engines is incomplete combustion in the cylinders.
Unburnt fuel washes lubricating oil off the cylinder walls causing rapid wear.
Unburnt fuel also gets past the rings and contaminates the motor oil.
This is called wash down. I can often tell a diesel engine that's been cold idled a lot just by sniffing the dipstick, smells like diesel.
It's the nature of the beast, diesel engines just don't warm up well idling.
Click to expand...
Couldnt agree more. When I first got my rig I would let it warm up in the driveway. Well, that wasnt exactly 5 minutes. At the time, I wanted the needle to move before Id want to drive, for more heat. Took forever for that too happen, like 30 minutes:shock:
Now if there is frost on the windshield, I simply warm it up for 5 minutes. Thats been enough to defrost the windshield before I go. Anything more than that is a waste.
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alanack6795
i know idle doesnt burn much fuel, when my friend took the motor out of a first gen he was scraping it ran for a while on just the fuel filters fuel.

So i should plug it in and give it 5 or so minutes? and keep it under 1500 whil its still "cold"
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e-rok
country_hick said:
Prolonged idling is generally considered not to be good for these trucks. The idle speed is to low. If you could get the idle up to about 1,500 rpm it would be a real improvement. Although this truck will not see winter roads my last (now rusted away) diesel did. All I really did was start it and get oil pressure up where it belongs. I might use high idle for a minute or so and then take off. I noticed on this truck I need to give some throttle for a minute or so in cold weather so the truck will idle above 500 rpm. When it warms up enough to idle well I take off. You may find you want to idle in neutral to refill the tc if you hesitate at first instead of taking off normally.

I would install a fuel pressure gauge (one that says oil pressure will work if you do not tell it that is not oil it is checking). Make sure you install something to smooth out the fuel pulses or it can destroy the gauge. That way you can see when fuel pressure drops and change the filter when it is needed instead of by mileage. You might go 100,000 miles and not plug up your fuel filter or it could get clogged from bad fuel in under 1,000 miles.

Additives except for anti-gel (in winter for summer fuel) are generally not needed.

My truck is a dually. I push around 2 more tires than you do.

I drove for good acceleration. I was accelerating at 2,000 rpm perhaps even 2,100. Driving locally I got a 16.25 mpg tank. I was unhappy with that number.

I watched my tach. I kept it at 1,250 to 1,500 rpm while accelerating. For 3 tanks I got 19.+ mpg.

That tells me that accelerating slowly saves fuel at least on a stock automatic.

Driving the truck home about 1,850 miles I got 23.5 and 26 mpg driving 1,500 rpm and 54 mph. I did 1,600 rpm once and get 1-2 less mpg. Close to home I pushed the speedometer up to 70 and about 1,900 rpm. I got about 18 mpg.

That told me that driving slower saved more than enough money to pay for a hotel room if it took an extra day of driving slower to get home.

One thing that will help mpg is a better torque converter. The stock one is about 65% efficient. A good aftermarket version is about 90% efficient. I was told that can be good for 1-3 mpg alone. Getting a tc with a stall speed of about 1,700 to 1,900 will also help you not to accelerate uselessly at 2,100 rpm and barely move forward.

Diesels like to run warm. However, whatever they like to do they drink more fuel when you are at higher rpms ( at least empty as a heavy load can change things).
Click to expand...
I always thought these things like to run at 1800-2000rpms. mine hates being at low rpms like 1200, but i have 35's. but my 2wd dually didnt like it either.

edit: I have a 5 speed, maybe thats why
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country_hick
e-rok said:
I always thought these things like to run at 1800-2000rpms. mine hates being at low rpms like 1200, but i have 35's. but my 2wd dually didnt like it either.

edit: I have a 5 speed, maybe thats why
Click to expand...
I would think with a stick you would want to be at 1,300 rpm minimum above 1st or perhaps 2nd gear. That would be the rpm you end up at when you just shifted into the next higher gear. Unlike an automatic you do not get torque multiplication before the tc locks up. I know with my tc locked up below about 1,250 rpm it feels like the engine is lugging or close to it. At 1,350 rpm or so the tc locks up normally and feels fine.

A buddy had a toyota yaris. He complained because he did not get the mpg it should. After going for a ride in his passenger seat I knew why he was getting lower mpg. He was revving 3,000 rpm or more most of the time. If I had been driving that yaris I would have been 1, perhaps 2 gears higher than the gear he was driving in at the same speed. Higher revolutions use more fuel compared to lower rpms unless a heavy load needs more rpm to allow the engine to become more efficient wile doing the hard work.

Bigger tires place more load on the engine. That alone demands a higher rpm. Just how much higher I would only be able to say after driving the truck for a few miles.
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alanack6795
My truck "feels" like it makes most of its power between 1500-1800 aftet that its just more noise really :buttkick:
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Mojave Magic
Keeping an eye on boost and fuel pressure can be a big help for mileage as well. This engine doesn't enjoy lugging down with high boost any more than it likes high rpm if you are trying to get good mileage. Watch the gauges and keep boost low and fuel pressure high and the engine won't have any choice, since you are sending less fuel its way. One trip as I was still learning, when towing my trailer, I got a full 1 mpg better running with OD off for an hour or two in the hills rather than lugging it.

Another trip we climbed the huge mountain up to Snowshoe WV (5,000ft) with the trans in 2wd low range (shift to 4 low and switch vacuum lines on the front axle) and got the same 13mpg I normally see on the highway running 65mph. That was doing 35mph at 2700 rpm for at least 30-40 minutes, but under 10lbs of boost, since there was less load on the engine.

For warm up, I plug in below 32. I also have an umbrella that I jam on the peddle to bump idle up to 1200rpm after oil pressure comes up. I'll fire it up, bump the idle and then go inside to put my boots on and grab my lunch and call it good.

Nice to see another truck with colors like mine, I've only seen a handful with this exact paint job. Here's mine when I first brought it home.
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dauntless89
country_hick pretty much nailed it.

Staying out of the skinny pedal is the best thing you can do for yourself. My rule of thumb is staying under 10-12 pounds of boost under acceleration and stick to the speed limit above 50 or so. Also, you can use the O/D OFF button to disable overdrive and enable 3rd gear lockup at street speeds. This will reduce transmission heat buildup and improve fuel economy between ~30 and ~45mph. I leave mine engaged until I hit 50, then I click it off.

Don't write off mods either, some can improve fuel economy and longevity, especially in the transmission. 17-18 is what I would expect for an average. I typically get 19-20 but there's a lot of 65mph highway driving and hills on my commute.

Don't cold idle the truck, it just wastes fuel and can clog up your cat. If you've still got a cat, you will need to get on it hard once or twice a tank. These cats need high rpm and high EGTs to burn off the soot otherwise it will get clogged and that alone can cost you 3 mpg and some amount of seat-pants performance.

I plug mine in at night but I have it set on a timer that comes on about an hour and a half before I leave. It slightly accelerates engine warm up but as far as that goes it doesn't matter if you plug it in for two hours or ten, it makes no difference with the thermostat bypass these trucks have. The main goal here is it makes things just warm enough that the grid heaters don't cycle, saving wear on my batteries, alternator, and grid circuits.

Keep an eye on your tire pressure too. That can make a difference. If you don't have the book that tells you what it should be, or have heavy bumpers, toolboxes, a flat/service bed, non-factory sized tires, a trailer you've always got hooked up, etc you can use an old circle track trick to figure out what your pressure needs to be:

Take some sidewalk chalk and color in a stripe across your tread, one tire on each end of the rig. Then drive a block or two in a straight line with no turning. If the chalk is worn in the center, it's over-inflated. If the chalk is worn off on the edges, it's under-inflated. If the chalk is scrubbed evenly, you're good.

Keep in mind tire temperature changes the pressure though, so for you your "winner" pressures may be cold pressures or hot pressures depending on whether you drive primarily at low speed around town or cruising on the highway. If you do a mix, get your tires good and warm and check the pressure, then let the rig sit overnight. Check the pressure (same tire) in the morning, and you'll have your cold/hot pressure differential (say the differential is 10psi) Then subtract half of that from your "winner" pressure (say 40 psi). You would then inflate to 35psi cold, knowing it'll go to 45psi hot. I'm totally anal and I have a summer inflation and a winter inflation that compensates for the change in high and low temp tire pressures. Probably overthinking it but whats a few minutes of my time if I get a few extra miles out of a $1000 set of tires?

The cool thing about this trick is you can do it when trailering and stuff too. Hauling your 5th wheel or a giant boat across the country? Hook that up and see how much you need to air up your rear tires to compensate. Test the trailers tires, see if the manufacturer's "recommendation" is correct. I've had some manufacturer specified pressures that were way off. You can also use this trick to intentionally under- or over-inflate a tire to correct abnormal tread wear caused by previous improper inflation.

Kinda went nutty bananas there, but yeah. Easy on the go pedal. Speed limits. Keep the cat clean. No cold idling. Transmission stuff. Tire pressure...
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Trumpf
Wow.. I learned alot from this thread so far!
I always thought letting my truck idle for a good while before taking off was the best thing you could do.
This is why I love this forum!
Now I have one question, after i take a 100 mile trip, should I let my truck idle before shutting it down?
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CTK30
When I drive around town I try to stay around 600* on the egt gauge while accelerating

Right now I get about the same on the highway and around town, usually 18-19 before tire size correction and 21ish after

Hopefully after putting the timing at 16* I'll pick some up on the highway

May do some aero mods to reduce drag too

shut down at less than 300* egt

Let it idle till it has oil pressure and idles smooth. Drive real easy until it warms up
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alanack6795
Mojave Magic said:
Keeping an eye on boost and fuel pressure can be a big help for mileage as well. This engine doesn't enjoy lugging down with high boost any more than it likes high rpm if you are trying to get good mileage. Watch the gauges and keep boost low and fuel pressure high and the engine won't have any choice, since you are sending less fuel its way. One trip as I was still learning, when towing my trailer, I got a full 1 mpg better running with OD off for an hour or two in the hills rather than lugging it.

Another trip we climbed the huge mountain up to Snowshoe WV (5,000ft) with the trans in 2wd low range (shift to 4 low and switch vacuum lines on the front axle) and got the same 13mpg I normally see on the highway running 65mph. That was doing 35mph at 2700 rpm for at least 30-40 minutes, but under 10lbs of boost, since there was less load on the engine.

For warm up, I plug in below 32. I also have an umbrella that I jam on the peddle to bump idle up to 1200rpm after oil pressure comes up. I'll fire it up, bump the idle and then go inside to put my boots on and grab my lunch and call it good.

Nice to see another truck with colors like mine, I've only seen a handful with this exact paint job. Here's mine when I first brought it home.
Click to expand...
Yeah i love the color, when i respray it ill try to keep it the same. Ive seen 2 others besides mine and yours

CAT? whats that i just have a downpipe :hehe:

Looks like im in the market for some gauges one of these days. That and a set of 285/75R16s probably another set of coopers.
So today it was 25-30F overnight i left the coolant heater plugged in all night started it up left it warm up for 5 more minutes and kept it below 1500rpm for a while, then after that kept it under 1800.

Im Grandma drivng this tank and see how much fuel i can save
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should I let my truck idle before shutting it down?
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Cummins says you only need to idle it after working hard like towing.
Some people say to idle until the pyro reads 350 or less.
Unless I've been working my trucks I shut them down as soon as I stop.
Seems to have worked fine for the past half million miles.
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alanack6795
illflem said:
Cummins says you only need to idle it after working hard like towing.
Some people say to idle until the pyro reads 350 or less.
Unless I've been working my trucks I shut them down as soon as I stop.
Seems to have worked fine for the past half million miles.
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Dam thats a lot of miles. Any secrets to keepin her goin that long
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JT422
There is a lot of great information in this thread. Everyone else hit just about all the nails on the head that I can think of, but I'll add a few things anyway.
-Drive slower, less RPM means you are asking the motor to do less work, and you'll save fuel.
-Don't idle your truck. If you want heat, put on a coat and drive until the heater is warm. I try to avoid idling my truck for longer than 5 minutes. If I have to sit in traffic or something, I keep the motor around 1250 rpm or shut it off.
Edit: I should clarify that I do high idle my truck when it is cold for a few minutes.
-Drive it easy. Semi trucks don't last a million miles because the driver shifted at redline and pulled every hill in the tallest gear he possibly could. I shift at 2k without the clutch and accelerate slowly, most of the time at least... I also use my gears to slow down. It really saves on brakes.
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alanack6795
JT422 said:
There is a lot of great information in this thread. Everyone else hit just about all the nails on the head that I can think of, but I'll add a few things anyway.
-Drive slower, less RPM means you are asking the motor to do less work, and you'll save fuel.
-Don't idle your truck. If you want heat, put on a coat and drive until the heater is warm. I try to avoid idling my truck for longer than 5 minutes. If I have to sit in traffic or something, I keep the motor around 1250 rpm or shut it off.
-Drive it easy. Semi trucks don't last a million miles because the driver shifted at redline and pulled every hill in the tallest gear he possibly could. I shift at 2k without the clutch and accelerate slowly, most of the time at least... I also use my gears to slow down. It really saves on brakes.
Click to expand...

Alright but brakes are cheap, Transmissions however, are not. And my truck is an auto. After i finish restoring my 1978 chevy k20 id like to buy a 12v 5 speed 2wd truck
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