lost MPG need help

[jrgough]

I had a bone stock 2006 2500 with 265/70/17 BFG All Terrains load range E tires and consistintly got 18-20mpg. I added the KORE HD leveling springs and Toyo ATs in the 285/70/17 load range D and are now getting 3-4 miles lower. I really like the way the truck looks, but dang with the price of fuel something has got to give. Is it the lift or the tires?

 

[Bernie]

Probably both:

Lift=Higher truck and therefore more wind resistance, more fuel needed to overcome the wind resistance.

Heavier tires=more torque needed to turn the tires, more power (fuel) needed to get them turning and keep them turning

More aggressive tires=more rolling resistance, and again more power is needed to overcome the resistance, and therefore more fuel is used.

 

[hearingyourlies]

Are you going hand calculated or using that stupid computer? Because if you haven't had the speedo adjusted you're actually going 62 mph when it says you're doing 60. Which means you've actually traveled 516 miles when it says you've traveled 500 ...

 

[jrgough]

no i have not hand calculated the mpg i was going from the overhead console reading which i now is not accurate but there has been a difference since the install. when i take off it also feels sluggish.

 

[Bernie]

Are you going hand calculated or using that stupid computer? Because if you haven't had the speedo adjusted you're actually going 62 mph when it says you're doing 60. Which means you've actually traveled 516 miles when it says you've traveled 500 ...

That math looks correct. You are traveling about 3% farther than your odo shows (and, about 3% faster).



Now, with that said if your 3-4 MPG loss represents a lot more than the 3% odo difference represents.



-Overhead reading 18-20 MPG. From experience, the overhead in my 06 was a lie-o-meter (while it is just optimistic in my 03). On my 06 I read 18, but was only getting 16.

-At 16 MPG, it takes 625 gallons to go 10k miles. That will cost you $3281 in diesel (at $5. 25 per gallon)



-With your new lift and tires, Overhead reading 14-17 MPG. I would guess, given the 06 gauge tendency to exaggerate you are probably getting 11 to 15 MPG. We will call it 13 MPG to do the cost.

-To adjust for your odo difference, 9700 indicated miles equals 10k actual miles traveled.

-It will take 756 gallons of diesel to go 10k actual (9700 indicated). That will cost you $3917 in diesel (at $5. 25 per gallon).



-756 gallons compared to 625 gallons is more than a 17% drop in fuel efficiency!



-So, if you go 10k miles per year, your new heavier tires and taller (more wind resistant) truck will cost you $636 in fuel per year.

-I travel about 50k miles per year, so for me that kind of loss would mean $3180 per year.



You can't just look at MPG. 1 MPG makes a big overall difference when we are looking at 10 MPG to 20 MPG range. It makes a lot less of a difference at the 30 MPG to 40 MPG range. I always recommend doing the math on what the fuel will actually cost you with your driving habits. That will give you a much better picture of what to expect.



I think the US is the only county to advertise MPG. Most other countries use the liters per 100 km formula. This is a much clearer picture of how much fuel you used.



Hand calculating your fuel usage and cost will always be the most accurate. However, for a quick reference when making fuel efficiency changes to your truck try the l/100km setting on the overhead console.