I have a couple questions puzzeling me if someone can give me their two cents worth. We have a 2000 3500 van, 5.9 gas and we have a k and n filter in it. I was at about 10mpg and cleaned and oiled the filter ( we live in az in lots of dust) also changed and put in new spark plugs. We left on a trip and the weather was warm and got 14.8 first tank 14.4 second tank then in the next 4 tank fill ups the best we got was 12.2 some were barely over 11.
The weather in the lower mpg was colder. and the k and n had more miles on it also. After the trip the k and n didnt visually look that dirty but may have been.?
My question is could a k and n suck in enough dust and shove the mpg down that bad that quick???? Or could the thermostat on the engine be either stuck or border line working temp causing the engine to stay in a closed loop they call it more in the colder driving?? This thermostat stuff and closed loop is beyond my experience but reading about it Im wondering if such a senerio is possible?? they dont look fun to change for just the practice . Such a drastic improvement the such a drastic drop in mpg has me confused.
Any Input appreciated
Thanks
Grumpy

 

Several things can factor in here. I don't think the K & N filter clogged up that fast. But driving speed, city/highway, headwind/tailwind, flat or mountin can factor in to the difference in economy. I have seen on my van a gain of 2 mpg by not driving over 60 on the highway. On my car I have seen 2 mpg gain by just dropping the speed from 70 to 65 mph.

I would suggest some more driving and logging of the type of conditions to see if this is random or normal.

 

YOu could be jumping the gun thinking the t stat is stuck open.

When cold, take the cap off the radiator and start the engine. Do you see the coolant moving right after a cold start?.

Otherwise, many other things can effect MPG. Do the key dance or whatever OBD2 vehicles need to do to pull the codes from the computer. If no codes then I'd suspect vacuum leaks, the before cat 02 sensor, then the 2 wire coolant temp sensor.

K&N air filters are one of those warm and fuzzies, which filters poorer than paper and adds no power benefit except at high rpm's, and no MPG benefit, in my opinion. I tossed mine and went back to paper after seeing hundreds of pin holes all around its perimeter and a throttle body with visible dust, in a not very dusty environment.

 

I did forget to include that we were on a mission to check the mpg because of the mpg we were getting all last summer and winter.
The miles per hr driven were kept very steady and it made a little dif when we upped the speed from 64-65 to 70 .
The milage i listed were all on pretty flat arizona and texas roads with pretty consistant weather conditions. All driven by same driver and doing 64 -65 with the cruise control.
My best guess is that as mentioned a sensor is probally messed up , I think im hoping something simpler and cheaper. I have no idea how to check these little genius things or anything about them. If there is a simple way to do that id like to know please.
Also any opinion on wheather the cheapest grade gas or higer up grade make a dif to amount to anything on these big vans on mpg??
Thanks again for all the input it really is nice to get the info.
Grumpy

 

My MPG takes a nosedive above 68MPH.

So many things can contribute to poor MPG.

Start by checking if any computer codes exist.

Sensors can be tested, some easier than others.

If your engine is not pinging on 87 octane, then no higher grade of gas is needed or beneficial.

 

I have an '01 2500 model (3500 chasis), 160K miles with the 5.2 and 4.10 rear end, work truck turned hiway cruiser and tow vehicle. If I do tow it is a light 16' aluminum boat, or an equally light, 8' aluminum popup camper. I also put in a K&N filter, new brass contact cap and rotor... have not touched the plugs yet. I think they were changed at 80K miles, but I have not had any mis-fire issues so I am leaving well enough alone.

My mpg varies, like yours from 14 to 9+. I usually only drive it on long multi-hour runs and the MPG is important to me. I know that headwinds certainly take a toll and tail winds, even slight help.

I rarely do 70... more like 65-67. I just can't do 55-60... I don't want other drivers think I am grandpa on a Sunday drive... If I am towing I step up every other tankful to 89 octane, and have been liberal with fuel additives, and last tried using the red Miracle Oil in a tank. Nothing seems to be consistant. I live in northern KY and we have some ups and downs on the interstate, but do lots of driving in OH and MI where it is pretty flat with mild hills.

I wish I could put my thumb on consistant better MPG... I have done all of the tricks that I learned from STEV in his MPG improvement post
https://dodgeforum.com/forum/dodge-r...rovements.html

I mostly use Flying J/Pilot gas on the freeway, although when not traveling I purchase the cheapest local gas I can find. I think variations in MPG come from different brands of gas.

I used to own a '94 B250 with the 5.9, and towing, or not towing my boat, I would almost always get between 12-14MPG... after wrecking the '94 I had hoped to better MPG wise with the '01 model.

 

We are on our fourth 360/5.9 15pass van, I cannot recall
achieving more than 12mpg (unladen) driving with a light foot.
When we pull a trailer I would say we get a reliable 8mpg.

 

I have a 2000 3500 ( W/ 5.9 ) Window Van and on Our last trip to visit family in Temecula , Ca. driving out and back from Mass. We averaged 10 to 12 in town and a steady 16 on the highway at 62-65 ..
With stops in Lake Havasu City and Kingman Az. area to play on a mining claim , then side trips to Bullhead City , Crown King , Payson , Prescott , and Deming Nm. for a little Rock Hounding on our way back to Mass. .
Bob

 

Bob ; i hope some day to get 16 but we live where you speak of, know the places well we go dabble in the dirt also you must be a gpaa member?

Were on those same roads you mention and get tops 12.4 now, mayb the 60 62 part, i usually run 64 or 65 sometimes even 68 or 69 but never down to the 60 unless law requires. guess i should learn to slow down; my wife may shoot me, she says i drive like a snail now she dont pay for the gas
Grumpy

 

If dropping down to 60-62 will get me 16MPG, then I am there! I'm usually not in a hurry anyway, but it is tough to not keep up with the traffic flow.