Extreme drop in MPG

[HunterBoy9]

2013 200. Had 33" KO2's on and routinely got about 18mpg. Made the jump to some 34.5 KO3's and fuel economy dropped to around 11. Went back to a set of Toyo Open Country RT in 265/70/18 (33.6") and mileage has not come back. Engine appears to be running as well as ever. just serviced all fluids. Could I have a fuel filter or something that just happened to go down at the same time as the tire swap?

 

[doru]

There is no fuel filter in the US production cruisers.
It may be a coincidence.
How did you measure it?

 

[HunterBoy9]

I am going strictly off the on-board display. I have reset a few times and tried different driving styles - highway,, around town etc.

 

[sdnative]

Maybe disconnect the battery for a few minutes and reconnect? This should force it to relearn driving behavior, fuel maps, etc.

 

[AZLX570]

18mpg is quite....impressive but not unheard of on just the highway. Have you tried only driving downhill with the new tires?

On a more serious note, what was the load range/weight of the old tires vs. new?

 

[Omega3651]

Have you tried ethanol free fuel for a couple tanks?
Engine runs way smoother and quieter with it.
Highway miles increased with it as well.
When I ran 295/70/18s my mileage never dropped below 15mpg mostly city use but I was getting 18 easily on the highway.

 

[Heckraiser]

@AZLX570 is on the right track. Tire size is only part of the equation. Tire weight can play a big part, as determined (in part) by load rating.

Also your original 33" KO2's were likely closer to 32" whereas your current Toyos are likely true to size and in reality closer to the 34.5 KO3's you had in the interim. BFG's tend to run smaller than spec in most sizes, sometimes pretty significantly smaller--about an inch.

 

[Sandroad]

And if your reading the on board display, use the tire diameter numbers from @Heckraiser and adjust mpg +/-

 

[bloc]

PCV valve could be contributing. Very cheap to replace with a Genuine Toyota part.

Also I'd support what Heckraiser said about tire diameter.

 

[bj70bc]

two posts above, and yes, small (lying) bfg's and big (real size) toyos

 

[GrouchyTech]

2013 200. Had 33" KO2's on and routinely got about 18mpg. Made the jump to some 34.5 KO3's and fuel economy dropped to around 11. Went back to a set of Toyo Open Country RT in 265/70/18 (33.6") and mileage has not come back. Engine appears to be running as well as ever. just serviced all fluids. Could I have a fuel filter or something that just happened to go down at the same time as the tire swap?

The Toyo is a 52lb, 33” tire. That’s where your mileage went.

My 61lb 285/65R18 KO3s get about the same 10-11 mpg city. Last year I borrowed a set of standard size/weight tires on some factory tundra 18s for two tanks and the mileage went back up to about 14 city.

 

[Supra Turbo]

Are you measuring the mpg accurarely and comparing apples to apples city vs city or highway vs highway (at the same speed)?

I ran 33" KO2s on my rig and got 18mpg highway, mostly around 65-70mph (75-80 would take a hit to 16).

Then I switched to 34" KO3s and my mpg drooped by 1mpg to 17mpg highway at the same speed (75-80 takes a hit to 15mpg).

 

[HunterBoy9]

@AZLX570 is on the right track. Tire size is only part of the equation. Tire weight can play a big part, as determined (in part) by load rating.

Also your original 33" KO2's were likely closer to 32" whereas your current Toyos are likely true to size and in reality closer to the 34.5 KO3's you had in the interim. BFG's tend to run smaller than spec in most sizes, sometimes pretty significantly smaller--about an inch.

The last set of KO3's rubbed at full lock, the new Toyo's do not so i take they are not quite as large a diameter. Weight may be different, as well as a little tread pattern difference. KO3 tires seemed to wear out faster than the OG KO2.