have a 46637 filter and 3" downpipe to 4" straight exhaust going in tuesday. just put on new 285/75 r16 tires aired to 50 rear 60 front. other than that stock for now. it has 209k miles. i run a zillion miles a year and just got this to replace the dodge 360 gas hog. so far i got almost 19mpg on the hwy at 65mph over a 150 mile trip and a total average of about 15.4 mpg through the rest of the two tanks with the remainder being city driving.

i drive like an old man and actually average about 30-35k miles a year. what else should i be looking to do to keep mileage up? also have a big ugly cap on it right now. probably going to take that off soon. haven't really decided yet.

i would honestly say 50% of the driving is unloaded, 35% with about 4-500 lbs in the back and 15% hauling a 7k lb trailer.


oh yeah, i love diesels!!!!! so far 500 miles in a week and i couldn't be happier!!!

 

Congrats on the new truck.
Mileage is best obtained with the mods you listed you are in the process of doing and driving like an old man. If you take off slow and try to keep the tach under 2000. Let off the pedal early when coming to a light and getting back on it easy.
I think some have gotten better mileage with smaller lighter tires but IMO I like the 285's you have. Mine are AT's but if yours are street tires you will do great. You are definately on the right track as far as mileage.

 

for me addind 2-stroke oil to the fuel was good for about 1mpg increase. Go ahaid and put a chip in you should see up to another 2mpg depending on your right foot. Taking the cap off will prob hurt your milage alittle because it helps streemline it.

 

That cap thing is debatable. I have seen many arguments on that topic. I say check it with it on and then with it off.

 

i am on the fence as for the cap. it may be growing on me a bit, and it is nice to have dry storage. i might just end up leaving it on. and i did go for an all terrain tire so that's kinda working against me.

what do you think about the cap's looks?





as for the truck i got a great deal on it and all it needed was tires, ball joints upper and lower on the pass side and axle u-joint same side. i did all the work myself so even with the tires i am out less than 5 grand!

 

so, does adding 2 stroke oil real work? and how much?

 

oh, ya, i get like 17 around town and thats driving pretty rough too. All i have done is a straight pipe, stock dp, k&n filter (I know i should get the 6637) and the ICP Resistance mod.

 

I recently started using Opti-Lube XPD and I love it! Increased my fuel mileage from 13-16 mpg(was getting 18-19 before the intro of ULSD) so it pays for itself while providing maximum lubricity to rubber seals in the fuel system, which ULSD deteriorates! I had 3-4 good size drip spots that stopped completely after just a few days. Runs way smoother,has around 10% more power and starts noticably easier. I guess im hooked. Theres a link i found on here with tons of info on additives, let me know if ur interested. Ed

 

Your cap will pretty much negate itself, it removes a large low pressure area behind the cab while making another one behind the tailgate.
If you want to do Aerodynamics, make a sloping cap that meets the top of the cab and the tailgate. it'll be ugly if it's right.
other than that, timing advanced and ICP increase, whether through chip or resistors will help.