Reman 1997 Chevy 5.0 bad gas mileage


Asked by May 20, 2014 at 12:17 PM about the 1997 Chevrolet C/K 1500 Cheyenne Extended Cab SB 4WD

Question type: General

I just had my mechanic install a Jasper remanufactured Engine in my 97 Silverado 2wd. I
just did a direct changeout (same size engine) 5.0 to 5.0. While this was being done I sent
my ECU out to be "tuned". With my old engine I was able to achieve 15 mpg average and
at its worst at the end we were looking at 13mpg. I now have about 5000 miles on the
reman engine and I havent got any better than 11.5 mpg since the changeout. Any ideas?
Could the tune be my culprit?  I also have a K&N intake, 3" catback exhaust, and a 3
chamber flowmaster. All of these I had for 5 years before I changed the engine. I also had
a new cat installed after the engine changeout too. Any help would be awesome! At this
point I can't afford to keep my truck or to get rid of it.

7 Answers


What did you do to the ECU? Tuned as in more performance? If so, you will use more fuel. Also a new engine will get worse gas mileage due to it being new and tighter internal tolerances. Once you get over 5K, you should see some improvement once the engine is broken in.

1 of 1 people found this helpful.

No, I wanted good fuel economy. I put a lot of miles on my truck.


OK, are the tires at the right pressure? Try cleaning the MAF, I see you put a K&N filter in, and if the oil from the filter gets on the MAF element , it could effect the MPG. Go to to see how. If so that checks out, then I'd wait a couple more thousand miles to see if the MPG improves before you get rid of it.

1 of 1 people found this helpful.

Yea everything is good. Having ac problems all of a sudden now. Could my ecu be bad?


check your fuel pressure/leakdown rate. Its a vortec engine with the spider injectors. The fuel pressure regulator is a known problem to fail and start leaking a little. Early sign is poor fuel economy. Just a thought, do you know what year 5.0 you swapped to? I'm wondering the cam it has

1 of 1 people found this helpful.

I have no idea what year they changed it out with. I will ask my mechanic to check the fuel pressure stuff as I do not have a Guage or knowledge to do so. Thank you for your help!


check your ecu the ac system works thru the ecu if your ac is malfunctioning is probably a good sign that theres an internal ecu issue I work on this models all the time goodluck godbless

Your Answer

C/K 1500

Looking for a Used C/K 1500 in your area?

CarGurus has 861 nationwide C/K 1500 listings starting at $2,988.


Chevrolet C/K 1500 Experts

  • #1
    Andrew Olsen
  • #2
    John Saffrahn
  • #3
View All

Related Models For Sale

Used GMC Sierra 1500
878 Great Deals out of 65,552 listings starting at $2,495
Used Ford F-150
2,316 Great Deals out of 184,579 listings starting at $699
Used Chevrolet C/K 2500
199 listings starting at $2,598
Used Dodge Ram 1500
356 Great Deals out of 10,908 listings starting at $1,500
Used Chevrolet C/K 3500
228 listings starting at $4,999
Used Chevrolet Tahoe
652 Great Deals out of 39,642 listings starting at $1,000
Used Toyota Tacoma
629 Great Deals out of 43,328 listings starting at $1,500
Used Chevrolet S-10
4 Great Deals out of 1,208 listings starting at $2,500
Used Chevrolet Camaro
417 Great Deals out of 30,917 listings starting at $3,550

Content submitted by Users is not endorsed by CarGurus, does not express the opinions of CarGurus, and should not be considered reviewed, screened, or approved by CarGurus. Please refer to CarGurus Terms of Use.