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Discussion Starter #1
So I bought my first diesel, a 1994 12 valve 4x4 today. I'm wondering what the best additives to use for fuel mileage are? I know that 2 stroke oil helps, but how much per tank, and does it matter if it's premium or not? Grateful for any help, thanks.
 

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Lots will Probly chime in on this but personally I think the only addative that should go in your tank is a good diesel/water treatment. I personally think getting more mpg out of a little bottle of addative is more snake oil and empty promises. Diesel fuel is a Natural lubricant and fresh/regular oil changes seem to help mpg. Synthetic oil in the diffs makes a Marginal difference as well but not overly noticeable. Save the 10-20 bux you'd spend on addative and put diesel in your tank.
Again this is all just my opinion.
 

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Two stroke oil is an internet myth. Real diesel additives MIGHT increase mileage, but so little that it will make your cost per mile increase. Diesel fuel is a commodity. Wal-Mart fuel is as good as high priced truck stop fuel. The best additive for mileage is your driving habits, and they are free.
 

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I don't add anything to the fuel in my Dodge truck because most ( but not quite all ) of the injection pump is lubricated by engine oil. Cummins even approves the use of kerosone as fuel in stationary generator/ pump application 6bt's that use P-Pumps.

The internet myth of two stroke oil seems to stretch pretty far a wide though. I was in a truck stop the other day (I'm not a professional driver so I'm not in them everyday), and the automotive isle had several different two stroke oils for sale in large bottles. So I'm guessing there's a market for two stroke oil at truck stops with semi drivers.
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So I'm guessing there's a market for two stroke oil at truck stops with semi drivers.
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I'm in truck stops a lot. Truck drivers rarely use actual fuel additives, I've never seen them use 2SO. Boat owners on the way to the lake or ocean are buying the 2SO.
 

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I'm in truck stops a lot. Truck drivers rarely use actual fuel additives, I've never seen them use 2SO. Boat owners on the way to the lake or ocean are buying the 2SO.

Okay, sounds reasonable enough. But there sure isn't much call for boat supplies on I-10 between San Antonio and El-Paso. I think the largest body of water within 500 miles was in the toilet.
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I fill up at buc’ees every morning and don’t use any additive. Truck runs great and gets 17 mpg with 35’s. Some get better mpg and some get worse but I’m pretty happy with 17
 

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Your worst enemy here is aerodynamics. Keep it at stock height with moderate size tires. Make sure your speedo gears are a match for the tires if you go up a size. That way you’re mileage will reflect correctly. I have the factory speedo gears in my truck with 35s, so I hand calculate every tank (downloaded a mileage tracker app). Have the air damn on the bottom of the bumper, and drive moderately with the pedal.


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But there sure isn't much call for boat supplies on I-10 between San Antonio and El-Paso. I think the largest body of water within 500 miles was in the toilet.
I guess you've never heard of Lake Amistad. There are others on the north side of I10, just not as famous.
 

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Discussion Starter #10
Thanks for your input everybody. I've got a 2.5" leveling block in the front and a 5" block in the rear, with 35's. Also aftermarket bumpers, so I won't have the air dam. I will download a mileage tracker app on my phone to get a accurate mileage readout.
 

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What kind of odometer gears would I need to change to to accurately measure the mileage with 35s?
 

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Check out this page. You’ll need to know rear end ratio
 

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[QUOTE="94CumminsRed, post: 29301528, member: 996403] I've got a 2.5" leveling block in the front and a 5" block in the rear, with 35's. Also aftermarket bumpers, so I won't have the air dam.[/QUOTE]

Not the best recipe for efficient use of fuel. If good mileage is a priority you have two options. Get rid of the lift, big tires and big bumpers or buy a rice burner. If you want to just improve what you are now getting it is the same old mantra. Slow down, ease off of stops and ease into stops. With proper driving habits you can get decent mileage, but I doubt it will be as high as 18mpg combined. I'm happy with the 15 I achieve. Changing speedo gears is a math problem. If you are showing 60 when you are actually doing 70 you need to install a gear that has fewer teeth. In that instance if your present gear has 30 teeth you would need one with 26. 60 divided by 70 (.857) times the number of teeth on your gear. (.857 X 30 = 25.7).
 
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I think I will just stick to putting diesel in, though I may run a little injector cleaner additive through it every once in a while. I already drive pretty conservatively, coasting before stop signs easing on throttle and braking lightly, so I'll just continue that. I'm probably only going to daily this truck for a year or so, then get a little beater car to drive to work and save this as a weekend cruiser/warrior. But thanks for your input everybody, it saved me from wasting money on a bunch of additives and 2-stroke oil.
 

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Changing speedo gears is a math problem. If you are showing 60 when you are actually doing 70 you need to install a gear that has fewer teeth. In that instance if your present gear has 30 teeth you would need one with 26. 60 divided by 70 (.857) times the number of teeth on your gear. (.857 X 30 = 25.7).
This is the first time I ever understood how to choose the right size speedometer gear. It is so simple that I had previously missed it completely.
 

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Stick to just diesel. Use the odd additive here and there depending on climates you live in and season/fuel changes. I’ve got a full Carli level kit on my truck with 35’s and I achieve an average of 12-13L/100km(~18-19mpg). Only additives I put in my truck is a cleaner in the spring and a cleaner in the fall for season changes around winter. Winter where I live get as cold as -40C for 4 months out of the year. Winter fuels get mixed in the pumps around here at those times and that’s the only time I use anti-gel additives. I do add 2 stroke oil once in a blue moon if I have it laying around. I ratio it 1:128(1 ounce for every gallon), just for the sole fact that ultra low sulfur diesel in pumps these days isn’t as lubricating as it was 20 years ago. I may be wrong on that, but I’m not concerned about the ~$50 a year it costs me and it can’t hurt.
 

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Ill throw my 2 cents in on this thread. First IMO the 12 valve does not really need additive. Because as said earlier in this thread the IP is lubed by engine oil.

ULSD as refined does not have much lubricity. It is very dry. As refined, It does not meet ASTM lube standards for diesel injection pumps. Additives are added by the fuel retailer to bring it up to ASTM standards...Barely. On IPs that are lubed by fuel only. Like Stanadyne pumps used on older GM diesels. Many people use TCW3 or other additives to keep the pump lubed and happy. It works well on those pumps and keeps them running fine on ULSD. Those older pumps were never designed to run ULSD so they need the extra lube.

If you do want to use 2 stroke oil for more lubricity. Use only TCW3 oil (Marine). It is formulated to leave no deposits.
Regular 2 stroke oil, the kind used in air cooled engines like chain saws. Will leave zinc and other deposits in the combustion chamber fouling the injectors. Mix at 1/2 to 1oz per gallon.
I do use Power Service white bottle in the winter in my 12 valve and in my GM 6.5 TD. For anti gelling and to add more Cetane which helps a bit for fuel MPG with winter mix fuel. Also to clean and lube the fuel system. It does not make much difference in my Cummins. But my 6.5 likes the extra Cetane because of its higher compression ratio.
 

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Ill throw my 2 cents in on this thread. First IMO the 12 valve does not really need additive. Because as said earlier in this thread the IP is lubed by engine oil.
Very true, the 12 valve IP does not need any additives, but neither does any other diesel engine IP. Only the bottom is lubed by engine oil. The number of parts lubed by fuel is greater than the number of parts in a VP44. Do you have anything besides the plethora of internet myths and fuel additive claims to support your claim that ULSD "barely" meets the needs of lubricity? The P-7100 was not designed for ULSD, so how does it differ from "Those older pumps"? It doesn't. The design is different, but the need for lubricity is the same. In 5000 miles my p-pump will go past 1.4 million miles without having any fuel lubed parts replaced. It has been in repair ONE time for an oil seal replacement. Ironic?
 

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Well if you have any experience with other older NON P700 pump diesels running a million miles. With no additives Please post it up.
I Have ran GM 6.2 and 6.5 diesels for over 20 years and beieve me. They do need lubricity fuel additives to keep the pumps happy. Unless you like replacing expensive IPs.
Go to the Diesel place in the 6.5 or 6.2 forums and post up what you just said. You will be laughed out of the place.
The P700 is a tough pump. The thing is huge compaired to a Stanadyne used in GM and older Fords. And is is a completely different design and operation. You cant compare them. Other pumps are not as tolerant of ULSD and all the contaminates it contains. Than the P700 monster. That will eat most anything. That is why I like it.
Altho this link is for storage tanks. And is explained in very simple terms. It does tell about how crappy ULSD without additives is for your fuel system.Ultra Low Sulfur Diesel (ULSD): the Good, the Bad, and the Rusty What comes out of those tanks goes thru your engine.
 
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