Engine/Transmission (1994 - 1998) highway and city mileage w/in 1 mpg???

[TLanier]

ive had my 12v for a couple months now. fillup before last, my truck got 18. 4mpg (about avg for me) with lots of inner city denver 5:00 traffic driving, mostly basic city driving, some highway, and some two lane roads up over the mountain passes in the rockies.



i took a road trip to santa fe, nm this weekend. filled up on the way out, and drove down I-25 with no headwind, and no mountain passes with the cruise set at 65mph. filled up and got a whoopin' 19. 6mpg.



to say i was disappointed is an understatement. i know this aint terrible, but i was expecting at least 20, if not the ever elusive 24mpg!



this is not much difference between city driving and slow highway driving. that seems odd to me. any ideas what could be the culprit?



my screen and fuel filter i changed with fleetguard. oil and filter too. timing i had bumped to 15. 5'. have a BHAF. truck runs smooth as silk at all rpms. starts immediately, with no stumble at all when cold. like a top! no leaks that i can find. i do have a #11 plate and a med spring afc. but i am VERY light footed when i want to be. the 18. 4 i got in city was not without a few smoke pouring seat of the pants accelerations, and the highway driving was "driving miss daisy". i am surprised.



what should i check? what should i replace? what mod should i make?



thanks all

 

[champspa]

that's about it , that's all I get , I have got 23 mpg once , 21 a few times but on the road 19. 5. If your looking for more your dreaming.

 

[tp0d]

At your elevation I`d be really happy to average city and highway at 19mpg. I`m at about 1500' here in PA, and I get about 17. 5 average city/hwy. I`ve seen 22 on long stretches of 60mph road, empty.



You can check your overflow valve for spring size (should be . 5 to . 55) and mebe stretch it a bit or replace it. Fuel pressure will hurt mpg easily. .



all in all i`d be happy with your current mpg. . dont think you'll see much more, 24 is a pipe dream in any ctd.



-j

 

[MLee]

TLanier;

Stock tires? or larger----if larger figure in the difference of distance traveled. As noted in other articles, any thing over 60 MPH the mileage starts to go down. I have read that for a true mileage test, "55" is the magic number to travel, under IDEAL conditions ETC.

Just my penny's worth.

Marv.

 

[sewman]

Once going 55-58 I got 24. 5 mpg,usually get 21 on the road w/a heavy foot

alittle better if I drive slower.

What gears do you have?I have 3. 55 & auto

Bob

 

[TLanier]

if im not mistaken, the top gear in the auto is a bit higher than 5th in the manual. dont quote me. i have 265/75 tires, so i checked the speedo by the mile markers on the highway yesterday. seems my speedo says 60mph when im doing 62mph. did the math, that means i got 19 city and 21. 25 highway. better.

 

[bkroupa]

My speedo is right at 10% off because of the 285/75 tires (GPS verified), but my odometer is only off by ~8% to the mile markers & GPS.

 

[JGK]

The 12 valves are very consistent between city and highway mileage. Mine varies only about as much as yours - a mile +/-. On the down side, people used to gassers expect better mileage when driving the freeway. On the up side, our city mileage is much better than a V10 or many V8 gassers. So look at it from the "half full" standpoint and enjoy the ride.



'Course, now hook up a load and pull it down the road and you'll see a change, but you won't like it!



-Jay

 

[TLanier]

is that possible for the speedo to be off one figure, and the odo to be off another figure? i thought they were connected, such that they should be the same in their accuracy?



yeah, i remember my '93 merc 300D got pretty much the same in town and hwy..... 29mpg. man i miss that car. it never left me stranded in 300k miles, and almost never needed repair. but when Greta needed work, she cost an arm and a leg for parts.

 

[bkroupa]

They're driven together but it's not unusual for the speedo & the odometer to differ.

My diesel bug's odometer was spot on, but the speedo was designed to read a couple of MPH fast. I read somewhere that in Europe they heavily fine the manufactures if the speedometer reads slow, so they all make them read a few percent fast.

 

[mjs]

I got less on the highway than country driving . That was from running 75 or so . I would like to see what 55 or 65 would do but don't have the patence , Mike