Gas mileage problems
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Senior User
Joined: Aug 2009
Posts: 252
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From: Brazoria, Texas
Gas mileage problems
I have a 89 f150 300 i6. When i first started driving it about 2 years ago i was getting about 16mpg but now im lucky to get 13mpg. Im driving the truck the same as i did 2 years ago. I have a K&N cold air intake and a flowmaster. ( im not driving it faster or harder because it sounds good) . Can y'all give me any tips please?
Laughing Gas
Joined: Jan 2008
Posts: 751
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From: NC
Try pulling codes.
Don't forget plugs and wires. Than K&N needs to be cleaned and re-oiled every 10-15K miles too. Tires? The right tires, pressure, and alignment can affect things. Clean out the throttle body for the fun of it.
Don't forget plugs and wires. Than K&N needs to be cleaned and re-oiled every 10-15K miles too. Tires? The right tires, pressure, and alignment can affect things. Clean out the throttle body for the fun of it.
Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
Get rid of the CAI. Its sucks in warm underhood air. The factory air box with the I6/460 tube is better. It actually gets cool air. Just run this with a good replacement filter not KN.
I agree about maintanance. Check the air in your tires. What plugs are you running?
Why would you want to replace vacuum hoses?
I agree about maintanance. Check the air in your tires. What plugs are you running?
Why would you want to replace vacuum hoses?
Elder User
Joined: Mar 2009
Posts: 769
Likes: 3
you would get better milage from a MAF Conversion they have them for all tranny types now Interactive Systems & Technologies Mass Air Home Page or dunnerite.com i am going to do my truck when i get the cash to do it.
Posting Guru
Joined: Jun 2003
Posts: 2,314
Likes: 0
From: southwest michigan
you could also check compression, might just be rings/seals are 2 years older.
does MAF give better mileage? This is a serious question, i'm not trying to argue.
i have two trucks, one rolled of the line in march 95, the other in Aug 95. Both are 351W/E40D/4x4 both ran the exact same (literally) 31" tires.
Everything is the same on these trucks except:
March Truck: Speed Density/3.55rear/long box
August Truck: Mass Air/3.08rear/short box
both get exactly the same mileage, 12City/13Hwy. Does this mean that There maybe something hurting my mileage on the Aug truck? How big of a difference should you see?
you would get better milage from a MAF Conversion they have them for all tranny types now Interactive Systems & Technologies Mass Air Home Page or dunnerite.com i am going to do my truck when i get the cash to do it.
i have two trucks, one rolled of the line in march 95, the other in Aug 95. Both are 351W/E40D/4x4 both ran the exact same (literally) 31" tires.
Everything is the same on these trucks except:
March Truck: Speed Density/3.55rear/long box
August Truck: Mass Air/3.08rear/short box
both get exactly the same mileage, 12City/13Hwy. Does this mean that There maybe something hurting my mileage on the Aug truck? How big of a difference should you see?
Last edited by skyfox10; Dec 10, 2009 at 07:43 PM. Reason: Addition
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FTE Legend
Joined: Jun 2006
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From: Ottawa, Ontario
Both trucks should do a lot better than that, have you recalibrated your speedos for the bigger tires? I'd also say that 3.55 gears is about the minimum for 31" tires and you could see milage improvements with a gearing change depending upon how fast you drive on the highway.
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Thread Starter
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Senior User
Joined: Aug 2009
Posts: 252
Likes: 0
From: Brazoria, Texas
Get rid of the CAI. Its sucks in warm underhood air. The factory air box with the I6/460 tube is better. It actually gets cool air. Just run this with a good replacement filter not KN.
I agree about maintanance. Check the air in your tires. What plugs are you running?
Why would you want to replace vacuum hoses?
I agree about maintanance. Check the air in your tires. What plugs are you running?
Why would you want to replace vacuum hoses?
Thread Starter
|
Senior User
Joined: Aug 2009
Posts: 252
Likes: 0
From: Brazoria, Texas
Both trucks should do a lot better than that, have you recalibrated your speedos for the bigger tires? I'd also say that 3.55 gears is about the minimum for 31" tires and you could see milage improvements with a gearing change depending upon how fast you drive on the highway.
Posting Guru
Joined: Jun 2003
Posts: 2,314
Likes: 0
From: southwest michigan
What type of K&N Intake do you have?
the old K&N FIPK's for the SD trucks.
or one of the newer ones:
57-2542 - K&N 57 Series FIPK, Performance Intake Kit (SD)
57-2543 - K&N 57 Series FIPK, Performance Intake Kit (MAF)
The newer filters have come a ways, and don't pull in as much warm air as the oder ones.
I have not recalibrate the speedos, I remember checking awhile ago and finding something like a 6% difference between stock and the 31's so I didn't find it significant (does this sound right?), plus i keep toying with 3.73's and didn't want to recalibrate them twice. When I get on the highway, i average 80, partially because it's necessary to stay in the powerband when i go through the mountains, but also I do enjoy the speed.
the old K&N FIPK's for the SD trucks.
or one of the newer ones:
57-2542 - K&N 57 Series FIPK, Performance Intake Kit (SD)
57-2543 - K&N 57 Series FIPK, Performance Intake Kit (MAF)
The newer filters have come a ways, and don't pull in as much warm air as the oder ones.
Both trucks should do a lot better than that, have you recalibrated your speedos for the bigger tires? I'd also say that 3.55 gears is about the minimum for 31" tires and you could see milage improvements with a gearing change depending upon how fast you drive on the highway.
Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
I don't have anything made by KN anymore. It lets more dirt in and it doesn't flow that well as it gets dirty. Also, all the cleaning drying and oiling is just a pain.
Also the fact that it can damage the MAF sensor is not worth it to me.
I had the KN FIPK for mass air but it is basically the same thing on my truck for a little while. Its a waste of money. All it did was decrease fuel economy and cause my truck to run really bad on hot days.
Even if the engine is not stock, the OEM air box especially with the I6/460 tube flows adequately.
Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
Many car manufacturers have TSB's about KN.
Most of the European car guys as well as the hot rod deisel guys won't run KN either. I also read that the exotic car shops won't use them either.
Here are a few links.
ISO 5011 Duramax Air Filter Test Report
Technical Articles: Debunking the K&N Myth - Why OEM is Better
Air Filters, Including My Thoughts on K&N
There are filtration and flow tests at the bottom of this link.
Air Filtration Test
Most of the European car guys as well as the hot rod deisel guys won't run KN either. I also read that the exotic car shops won't use them either.
Here are a few links.
ISO 5011 Duramax Air Filter Test Report
Technical Articles: Debunking the K&N Myth - Why OEM is Better
Air Filters, Including My Thoughts on K&N
There are filtration and flow tests at the bottom of this link.
Air Filtration Test
Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
I believe that since your truck is an 89, you have to change your speedo gear to recalibrate for the tires. The 92-96 can actually be reprogrammed.