Post by: Crunchy on March 06, 2018, 05:56:42 PM
Post by: trophyhunt on March 06, 2018, 06:01:00 PM
Post by: netcoyote on March 06, 2018, 06:17:37 PM
You can get aftermarket devices that plug into the OBD port to flash the computer to compensate for change in tire size. It will recalculate shift point also.
Post by: Crunchy on March 06, 2018, 06:41:12 PM
Post by: jackelope on March 06, 2018, 06:57:35 PM
Post by: jackelope on March 06, 2018, 06:58:49 PM
Post by: netcoyote on March 06, 2018, 07:39:54 PM
Nothing dramatic on size, I went from a 295/65/20 to a 285/70/20
Yea, that's not much of a change at all. Only works out to about 10 revolutions per mile less. Hardly enough to make any noticeable difference. Could be your truck is more sensitive than some or, like someone else mentioned, maybe the shift in fuel blend.
Post by: Crunchy on March 06, 2018, 07:44:13 PM
Post by: trophyhunt on March 06, 2018, 07:54:59 PM
Post by: Special T on March 06, 2018, 07:58:55 PM
Sent from my SAMSUNG-SM-G930A using Tapatalk
Post by: trophyhunt on March 06, 2018, 08:01:55 PM
Fuel filters are cheap. Lots of crappy fuel out there. I keep an extra stock spare in the truck.I change my fuel filter every other oil change, and coach told me to add fuel additive with every tank.
Sent from my SAMSUNG-SM-G930A using Tapatalk
Post by: Special T on March 06, 2018, 08:04:29 PM
Sent from my SAMSUNG-SM-G930A using Tapatalk
Post by: Boss .300 winmag on March 06, 2018, 08:06:15 PM
I’m sure all the programmers have this option.
Post by: jackelope on March 07, 2018, 10:17:14 AM
Check tire pressures, check air filter, if it's a diesel, replace fuel filters religiously every 12k-15k miles. Winter will drop your mpg in a diesel a bit for sure. I betcha that's your only problem. How many miles on the truck? Did you add anything to it other than the tires?
Post by: Alchase on March 07, 2018, 10:30:36 AM
Any increase in either weight or resistance will decrease your MPG, and performance.
Post by: Crunchy on March 07, 2018, 01:58:35 PM
Post by: Alchase on March 07, 2018, 02:52:51 PM
The truck has 9500 on it. I will look into some kind of fuel additive. Fuel filter has another 22% before the comp says they are needing to be changed.
Crunchy, what vehicle and motor?
Only 9500 miles, and you saw a noticeable MPG decrease?
Shouldn't it be under warranty? I would have them check it out.
Post by: Crunchy on March 07, 2018, 02:58:31 PM
Post by: Alchase on March 07, 2018, 03:08:26 PM
Nothing dramatic on size, I went from a 295/65/20 to a 285/70/20
Yea, that's not much of a change at all. Only works out to about 10 revolutions per mile less. Hardly enough to make any noticeable difference. Could be your truck is more sensitive than some or, like someone else mentioned, maybe the shift in fuel blend.
For a Ram 2500 with the Cummings, I would bet the tire change was insignificant to the issue.
Post by: Crunchy on March 07, 2018, 03:16:57 PM
Fuel filters are cheap. Lots of crappy fuel out there. I keep an extra stock spare in the truck.I change my fuel filter every other oil change, and coach told me to add fuel additive with every tank.
Sent from my SAMSUNG-SM-G930A using Tapatalk
which additive did he recommend?
Post by: Special T on March 07, 2018, 03:19:34 PM
I would bet that that 22% sat is based off mileage, just like the oil change stuff is. OR idling your your Cummins to warm it up is having an effect on your Emmisions garbage.
The fuel filter on my dodge is less than $25. Any noticeable difference in mileage pays to put in a new one.
All that computer calculated output is just bells and whistles. Unless there is some kind of fuel drag/resistance sensors I'm 99% certain it's based on mileage, just like how check engine light tend to come on during service intervals. 2c
Sent from my SAMSUNG-SM-G930A using Tapatalk
Post by: jackelope on March 07, 2018, 03:39:53 PM
The truck has 9500 on it. I will look into some kind of fuel additive. Fuel filter has another 22% before the comp says they are needing to be changed.
Crunchy, what vehicle and motor?
Only 9500 miles, and you saw a noticeable MPG decrease?
Shouldn't it be under warranty? I would have them check it out.
He put bigger tires on it and it's winter.
There's nothing wrong with the truck.
:twocents:
Post by: jackelope on March 07, 2018, 03:42:19 PM
Fuel filters are cheap. Lots of crappy fuel out there. I keep an extra stock spare in the truck.I change my fuel filter every other oil change, and coach told me to add fuel additive with every tank.
Sent from my SAMSUNG-SM-G930A using Tapatalk
which additive did he recommend?
Maybe a quality cetane booster?
Post by: Woodchuck on March 07, 2018, 03:55:09 PM
Post by: jackelope on March 07, 2018, 03:57:42 PM
I went up 8% in tire size and saw a decrease in Hwy milage...
I would bet that that 22% sat is based off mileage, just like the oil change stuff is. OR idling your your Cummins to warm it up is having an effect on your Emmisions garbage.
The fuel filter on my dodge is less than $25. Any noticeable difference in mileage pays to put in a new one.
All that computer calculated output is just bells and whistles. Unless there is some kind of fuel drag/resistance sensors I'm 99% certain it's based on mileage, just like how check engine light tend to come on during service intervals. 2c
Sent from my SAMSUNG-SM-G930A using Tapatalk
That fuel filter % is based off of a combo of miles, engine hours and engine work load.
Same way as our oil change intervals work now.
Post by: trophyhunt on March 07, 2018, 04:38:34 PM
Post by: jackelope on March 07, 2018, 04:40:28 PM
Post by: trophyhunt on March 07, 2018, 04:53:37 PM
Your speedo is definitely not accurate. I would assume you're losing some performance because of it too. Shift points will be off, etc.yes, Speedo is off, it still shifts nice but I’m positive it could be better. My diesel mileage sucks, about 11.5 per gallon pulling a loaded trailer or not.
Post by: Crunchy on March 07, 2018, 04:57:57 PM
Your speedo is definitely not accurate. I would assume you're losing some performance because of it too. Shift points will be off, etc.
Dealership job, or other options? When I first got the truck I was averaging about 16, after it broke in I was getting nearly 20. Now it has shot down to about 16 again. Other than tires, and an oil change nothing has changed.
Post by: horsehunter509 on March 07, 2018, 06:17:14 PM
The truck has 9500 on it. I will look into some kind of fuel additive. Fuel filter has another 22% before the comp says they are needing to be changed.
I never run mine to 0%. Normaly do fuel filter between 20-25%. Not worth pushing it any further for me.
Post by: jackelope on March 07, 2018, 09:08:03 PM
Your speedo is definitely not accurate. I would assume you're losing some performance because of it too. Shift points will be off, etc.
Dealership job, or other options? When I first got the truck I was averaging about 16, after it broke in I was getting nearly 20. Now it has shot down to about 16 again. Other than tires, and an oil change nothing has changed.
As far as programming for tire size, as far as I know, a dealer can’t program for an oversized tire like that. Only another factory tire size. I can tell you for sure that Dodge and Ford dealers can’t do it. I assume the same for a GM dealer.
Post by: jackelope on March 07, 2018, 09:09:14 PM
Your speedo is definitely not accurate. I would assume you're losing some performance because of it too. Shift points will be off, etc.
Dealership job, or other options? When I first got the truck I was averaging about 16, after it broke in I was getting nearly 20. Now it has shot down to about 16 again. Other than tires, and an oil change nothing has changed.
Are you actually calculating it or going off what the truck is telling you?