Horrible mileage after tune?
11-03-2018, 09:51 PM
#1
Senior Member
Thread Starter
Horrible mileage after tune?
Has anybody seen a huge drop in mileage after tuning? I used to have a 2011 5.0, level, 33" tires and a 5 star tune. Interstate with the cruise set, 17.5 all day long. I now have the 2018, same truck, same gear ratios, everything. 5 star tune, level, except 34" tires, 1 more inch. Interstate with cruise set? 12. thats it. 
Before tires and tune i was getting 18.3. The 2011 almost got that with all the extra stuff on it. Is it possible that the tune could have a problem? I may return to stock and see what it does, to see if it is the problem itself. I don't know much about tuning, could there be an issue with the tune? I just can't imagine that the same truck 7 years newer, and 700 pounds lighter overall at that, could get 5 and half mpg less than my old one that had 173,000 miles on it. Makes me wonder if something is wrong here 
Before tires and tune i was getting 18.3. The 2011 almost got that with all the extra stuff on it. Is it possible that the tune could have a problem? I may return to stock and see what it does, to see if it is the problem itself. I don't know much about tuning, could there be an issue with the tune? I just can't imagine that the same truck 7 years newer, and 700 pounds lighter overall at that, could get 5 and half mpg less than my old one that had 173,000 miles on it. Makes me wonder if something is wrong here
11-03-2018, 10:18 PM
#3
Senior Member
Thread Starter
11-03-2018, 10:20 PM
#4
Senior Member
Do you have your speedometer and odometer adjusted for the difference in tire diameter? With the larger tires, you are actually traveling about 6% further than your odometer says. So youre really getting about 13mpg instead of 12. But thats still a pretty big disparity even with the correction factor.
The bad thing about "canned" tunes or mail-in tunes is not everu truck is made the same... One truck may like a little more timing than the next truck etc. Thats why a custom tune really needs to be done in person on the street or dyno while being monitored in real world conditions. Your truck could actually be running worse than stock because of some parameter from your mail-in tune that just isn't jiving with your truck.
The bad thing about "canned" tunes or mail-in tunes is not everu truck is made the same... One truck may like a little more timing than the next truck etc. Thats why a custom tune really needs to be done in person on the street or dyno while being monitored in real world conditions. Your truck could actually be running worse than stock because of some parameter from your mail-in tune that just isn't jiving with your truck.
11-03-2018, 10:26 PM
#5
Usually, it's not a fault of the tune... it's the fault of the guy behind the wheel having too much fun with said tune. Mine isn't tuned, but driving it in a "spirited" manner (such as responding to a fire call) will completely tank the fuel economy.
11-03-2018, 10:37 PM
#7
yes, i understand how vehicles work.
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11-03-2018, 10:45 PM
#8
Senior Member
Thread Starter
Yea it should be calibrated for the tires, he asked me what size they were, unless he forgot to put them in. I need to find one of those digital speed signs somewhere. ha The power is definitely there, but on the interstate i'm not playing with it, so it should even out. Do you think its worth sending back to get rewrote or adjusted, or is any adjustments just going to be a guessing game since they dont have the truck?
11-03-2018, 10:56 PM
#9
Yea it should be calibrated for the tires, he asked me what size they were, unless he forgot to put them in. I need to find one of those digital speed signs somewhere. ha The power is definitely there, but on the interstate i'm not playing with it, so it should even out. Do you think its worth sending back to get rewrote or adjusted, or is any adjustments just going to be a guessing game since they dont have the truck?
do a few datalogs with your tuner and send them back to the tuner. they should be able to clean up the tune. it's not so much ignition timing with these motors as it is cam timing and fuel and i think that might be the problem.
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79lance (11-03-2018)
11-03-2018, 11:21 PM
#10
Senior Member
Thread Starter
Do you have your speedometer and odometer adjusted for the difference in tire diameter? With the larger tires, you are actually traveling about 6% further than your odometer says. So youre really getting about 13mpg instead of 12. But thats still a pretty big disparity even with the correction factor.
The bad thing about "canned" tunes or mail-in tunes is not everu truck is made the same... One truck may like a little more timing than the next truck etc. Thats why a custom tune really needs to be done in person on the street or dyno while being monitored in real world conditions. Your truck could actually be running worse than stock because of some parameter from your mail-in tune that just isn't jiving with your truck.
The bad thing about "canned" tunes or mail-in tunes is not everu truck is made the same... One truck may like a little more timing than the next truck etc. Thats why a custom tune really needs to be done in person on the street or dyno while being monitored in real world conditions. Your truck could actually be running worse than stock because of some parameter from your mail-in tune that just isn't jiving with your truck.