what are you guys doing to get the best mileage out of your 95 12Vs? iv heard tons of guys say 28-30mpg is easily attainable but just not sure how to get there.......

 

i drove like a grandma and got twenty once, most of the time 15 or 16. i'm happy with that big truck, 4.10's.

 

15hwy mgps on a stock 5.9???? i wouldnt b happy with that, my 5.7 hemi got 20 mpg at 60mph. its gotta b better than that. maybe ur #10 plate is why yours is somewhat lower......

 

well actually its better now, with the plate and injectors, then it was. its only ten miles to work on a county blacktop and some country roads and i go through three stop signs. i bet it only sees the highway once a week maybe, so thats why i have settled with what i have for mileage. i have a friend with a 06 1500 4x4 hemi and he gets 15 tops, and he all highway, so maybe its the fuel or the area we live in. i'd love to get 20 mpg min. but?

 

i have an '97 3500 and easily get 17 to 19mpg with combined city and highway driving. low 20's are pretty easy on trips with 26mpg being the best. it has the 5spd with 3.54ratio axles. if i drive it fast than 75mph the mileage starts to drop, but thats fast enough for me anyway.

 

what have you done to your truck to get that, jig? i would be happy with 25 mpg...

 

I have only owned my truck for little while but did a hand calc combined 23.5 and thats with about an hour of idle time plub average 3-5 minute warm up daily. It has a k,n intake and a 4" exhaust with no cat. As far as other mods I dont know. Hope that with help baseline wise.

 

I don't think 28-30 is "easily" obtained. Over 20 takes a lot of carefully planned driving for me, but is possible even with winter fuel. Lifts and big tires are not good for mileage. My highest ever was just over 24, good summer fuel and skinny's pumped up to 70 psi cruising at 55 or so for a few hundred miles. Got almost 700 miles out of that tank!

Free flowing exhaust does help, as is timing advance to 15.5-16*. I try to keep boost between 5-10 for best mileage.

 

They say that a pesimisist is an optimist with experience.
I am pesimistic that someone is getting 28-30 mpg out of their trucks. Two factors play into this belief- people stretch the facts sometimes (I do, too), and it appears that getting a true average for mileage takes a lot of miles, and careful calculating. My stock 5.9 is in good shape, with almost stock tires (285's), 3.50 gears, and reasonable driving, and I find it hard to consistently break 20 mpg. Most of my driving is local/city driving. I know that highway mileage is better, but another 10 mpg is quite a feat.
I'm not trying to be harsh- what I am getting at is that 20 mpg for a 7000 brick is pretty good. Lots of small trucks don't do that good.

 

thanks hodge, i was thinking i was only one under twenty. when i running down road at anything over 65, empty i'm pulling 14+ lbs boost at 2100+ rpm on flat ground which is why i don't expect great mileage.

 

i see. i must have been confused with the gen 1 cummins getting that then, cause iv heard it lots but im gonna do my own calculations now, and an exhaust and intake are coming shortly so it will be interesting to see if that helps any

 

i know i have a 98 12v but the best i have got was 25.6 hand calc with stock 245 tires and keeping it under 50 straight highway miles but 60 and below i get 22 constantly

 

I drive mine kinda hard, not wot, but like to get moving, with 295/75r16 and 4:10 gears I get hand calculated 16mpg. Still cheaper than a payment! And yes, the 295's scrub when turning......need some kinda lift, but hard to find for a 2wd.

 

i'm not completely sure what all has been done as far as with the pump and timing etc. i have a buddy that has a shop in miles city, mt that is a wiz at that and he had the truck all set up when i bought it from him. i know the pumps is turned up some but not a lot. straight exhaust, replaced the dually rearend with single wheels, 285 tires, and i add a quart of atf every tank of fuel. i did make 42 mpg on one stretch last trip back from snowmobiling, but idling in 5th gear for 10hrs to go 300 miles on icy roads wasn't worth the money saved on fuel.

 

The single best mod for more mpg and power is to raise the timing up to 15-16.
I consistently get 22-24 mpg highway, no city close enough to drive in.

Good reading here> Cummins Secrets of Better Fuel Economy - The Physics of MPG