Gas mileage and computer accuracy with different sized wheels.
#1
02-29-2012, 01:32 AM
Gas mileage and computer accuracy with different sized wheels.
I have an 02 Dodge Ram 1500 SLT with the 5.9 L. only Mods are a Magnaflow cat-back system and a K&N Cold air intake.
It seems im getting really poor gas mileage (9.4 according to the trip computer). i know not to expect good gas mileage but that seems lower than it should. i do have 20inch wheels on it. those were the ones on it when i bought the truck. i believe that stock wheels on this was 17 inch. could the 20 inch wheel make either the gas mileage go do or make the computer off?
another question is about my gas tank. its the first dodge ive owned so im new to it. when my gas light comes on(when its less than 1/8 of a tank) i go to put gas in and it only takes a little over 22 gallons. could there still be 4 gallons still in there?? thanks for the help!
It seems im getting really poor gas mileage (9.4 according to the trip computer). i know not to expect good gas mileage but that seems lower than it should. i do have 20inch wheels on it. those were the ones on it when i bought the truck. i believe that stock wheels on this was 17 inch. could the 20 inch wheel make either the gas mileage go do or make the computer off?
another question is about my gas tank. its the first dodge ive owned so im new to it. when my gas light comes on(when its less than 1/8 of a tank) i go to put gas in and it only takes a little over 22 gallons. could there still be 4 gallons still in there?? thanks for the help!
Last edited by drave199; 02-29-2012 at 01:39 AM.
#2
02-29-2012, 07:02 AM
Yes 20" wheels are significantly heavier than 17" wheels and will negatively effect both performance and MPG. However, if the tire diameter is the same as stock then the speedometer/trip computer/etc. won't be off. If you are running larger diameter tires than stock, then you are getting better gas mileage than the odometer or trip computer would indicate.
You have a VERY stout engine and many guys on here have well over 200,000 miles on that 5.9, but you need to remember, it was basically engineered in the 1960s, with only minor changes (like fuel injection) through the years, so it's HP per displacement and MPG are pretty poor when comparing to modern engines. The Hemi for example, is slightly smaller at 5.7L, but makes over 100 more HP while getting a good 25% better fuel economy.
Yes, it's not uncommon to have 3-4 gallons of gas still in the tank when the gas indicator goes off...
You have a VERY stout engine and many guys on here have well over 200,000 miles on that 5.9, but you need to remember, it was basically engineered in the 1960s, with only minor changes (like fuel injection) through the years, so it's HP per displacement and MPG are pretty poor when comparing to modern engines. The Hemi for example, is slightly smaller at 5.7L, but makes over 100 more HP while getting a good 25% better fuel economy.
Yes, it's not uncommon to have 3-4 gallons of gas still in the tank when the gas indicator goes off...
#3
03-02-2012, 02:15 PM
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Yes 20" wheels are significantly heavier than 17" wheels and will negatively effect both performance and MPG. However, if the tire diameter is the same as stock then the speedometer/trip computer/etc. won't be off. If you are running larger diameter tires than stock, then you are getting better gas mileage than the odometer or trip computer would indicate.
You have a VERY stout engine and many guys on here have well over 200,000 miles on that 5.9, but you need to remember, it was basically engineered in the 1960s, with only minor changes (like fuel injection) through the years, so it's HP per displacement and MPG are pretty poor when comparing to modern engines. The Hemi for example, is slightly smaller at 5.7L, but makes over 100 more HP while getting a good 25% better fuel economy.
Yes, it's not uncommon to have 3-4 gallons of gas still in the tank when the gas indicator goes off...
You have a VERY stout engine and many guys on here have well over 200,000 miles on that 5.9, but you need to remember, it was basically engineered in the 1960s, with only minor changes (like fuel injection) through the years, so it's HP per displacement and MPG are pretty poor when comparing to modern engines. The Hemi for example, is slightly smaller at 5.7L, but makes over 100 more HP while getting a good 25% better fuel economy.
Yes, it's not uncommon to have 3-4 gallons of gas still in the tank when the gas indicator goes off...
#4
03-02-2012, 03:32 PM
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The wheel diameter themselves will not effect the reading on the computer but if the overall diameter of wheels/tires had been increased, then it would be off. My truck stock had 245/70/R17's on it and I then went to 35" tires. Basic conversion turns the stock tires to 30.5 inches tall and my 35" Cooper STT's show 34.7 on tirerack (roughly) which is a little more then 10% taller. All around for my truck shows 12/12.5 on the puter usually. I just add 10% for quick simplicity which takes actual all around for my 4.7 4X4 to roughly 13.5 real MPG's. Of course my odometer just passed 50000 so in reality I have put about 55000 since new.
A few othe notes as 10% +or- a tad seems to be the usual increments for me. If I put my stock tires back on I am up another 10% to around 15 MPG all around. (actually 20% by computer as it goes back to an accurate reading). I lost another 10% by leveling it which means for the first several thousand miles on my truck I was getting about 16/16.5.
Another bit I found was I traded in a 04 4.7 2WD for the 07 4X4 and I was getting in the mid 17's all around and saw 18 a bit as well. Upwards of 20 on the highway. So that front axle and transfer case seemed to knock 10% off as well from what I was used too.
A few othe notes as 10% +or- a tad seems to be the usual increments for me. If I put my stock tires back on I am up another 10% to around 15 MPG all around. (actually 20% by computer as it goes back to an accurate reading). I lost another 10% by leveling it which means for the first several thousand miles on my truck I was getting about 16/16.5.
Another bit I found was I traded in a 04 4.7 2WD for the 07 4X4 and I was getting in the mid 17's all around and saw 18 a bit as well. Upwards of 20 on the highway. So that front axle and transfer case seemed to knock 10% off as well from what I was used too.
