MPG with skinny tires (255/85/16)

I’m running Cooper ST’s on stock rims. I’m getting 14.7 per the computer. That’s not accounting for additional tire height or anything. What are you guys getting? I dont Drive especially hard and even on the highway I dont Get much better. What are you all getting on skinny tires running 70-75-80mph?

 

Has your speedometer been recalibrated after the tire size increase? Based on the average size 255/85/16 tire increase from a stock OR size 265/70/16 you have approximately 8% speedometer error according to the tire size calculator so if you think you're doing 65 you're actually doing 70mph, 70mph on the speedo then 76mph actual and so on.

My experience with a 265/70/17 is mpgs drop significantly when running over 70mph.

 

Problem is the tires are much heavier than your stock tires as well. Yes skinnier tires will have better MPG than a same weight tire that is wider, but ultimately going to be a loss in MPG due to tire weight and changing the aerodynamics of the vehicle.

 

If you’re going to be running over 75MPH don’t expect to get good MPG.

I don’t have thag size tire but if I keep it under 70MPH my MPG’s do well, anything over and it starts dropping.

 

If you haven't regeared and or recalibrated the speedo, then don't bother checking the computer for mpg. It thinks you have traveled much less than you really did. Therefore it shows a low mpg. Fill it with fuel. Get on the highway. Watch the mile markers and run out 10 miles. Compare to your trip meter. Find percentage of difference. Now burn up that tank of fuel. Fill her back up and record how many gallons used and how many actual miles traveled. Now you will know.

 

Ditto ^^^^^ same with 295/70/17 and 4:88’s keep it at 70 or under for best MPG results

 

I’m getting 15.8mpg when adjusting for the tire size driving like a normal person. There’s no way to justify that, IMHO.

 

Justify what?

 

Ignore the dash. It doesn't know what's going on. GIGO is at play here.

Calculate by hand. Use the Tire Calculator to get the % delta in your old and new tires, which 'corrects' your odo reading for calculating purposes.

Because of larger circumference, you aren't recording as many miles as actually being driven. Think of it as a way to extend your warranty period.

You've also decreased your final drive ratio. Meaning you should be at less RPM for a given MPH, which is good for MPG. However, you've added weight, rolling resistance and impacted (negatively) aero of the truck.

Every mechanical mod is a trade off of something, improving one thing at the cost of another.

 

Hmmm I got 18.8 mpg from Las Vegas to Carmel recently, even with my setup.

To be perfectly frank tho, when I changed gears , suspension and tire size...I really did not care about MPG anymore! If you do that kind of mods it’s going to effect your mpg’s period...still I was shocked after doing the math !!!

 

The adjusted MPG is 15.8. Most people are getting 19ish with similar mods.

 

Obviously there is a trade off but you’re getting 3 more mpg than me. That’s SIXTY MORE MILES BETWEEN FILL UPS

 

Ahhhthen perhaps it’s the operator?

 

I drive Like grandpa.

 

I was surprised at the MPG from thAt trip, typically lower , but a lot of that is bacause of my driving habits

 

That could be it !
Depending on which grandpa were talking about lol

 

I'm a grandpa and drive 70mph and below, sounds like you dont drive like me.

What's your elevation where you drive and how much of your drive it stop and go?

 

His screen name would indicate he drives below sea level with continuous stop and go.

But he may have moved. Or live out from NOLA somewhere.

 

Just outside of Nola. Even on trips my mpg is shit.

 

Are you lifted at all?
When I was driving with more of a lead foot bringing up the RPM’s to 3000-3500 from a stop and constantly going 75-80 on the freeway, I was getting anywhere from 14.5MPG-15.3MPG.

Once I stopped doing that and kept my RPM’s below 2000 from a stop and going 65-70 my MPG’s went up. I am now at 17.8MPG.
I have 275/70/17, E rated tires also.