Under 8 MPG

[sbman]

This likely wont help with mpgs but what do you mean by "factory?" The OEM tires were a P-Metric tire and if your tires are currently an LT you would need to look at load inflation tables to have the correct PSI.

e.g.

P275/70R16 = 2480 at 32 PSI / 1.1 derated P tire = 2255
LT275/70R16 = 2295 at 45 PSI (Load inflation must be equal to or greater)

So I would double what your tires are P, SL, LT etc and what the corresponding PSI is.

This. Probably not the source of your issue, but possibly a contributing factor. If you are running LT tires and inflated to the P metric PSI you can see an 8-10% mileage hit from being under inflated. Factory pressure spec is only applicable to factory tire spec.

 

[elripster]

Well, I’m currently at the mercy of the shop.
Currently out of town for another couple weeks. Dropped off the rig before I left, wanted it fixed while I was away.

Makes sense. I usually fix my own stuff but kid #4 came along when my engine needed rebuilding and I punted.

Owning old trucks seems to present us with two paths, we learn the trucks and trade our time for money, or we pay someone else and do the same in the other direction.

If this shop seems to be stuck and time is in short supply, Cruiser Tech is in Laguna Hills and I have been hearing good things about them. Georg Estere / Valley Hybrids is farther away in Stockton but is exceptionally knowledgeable and has an outstanding reputation in the cruiser community. I have done business with Valley Hybrids many times and personally recommend them. I dealt with a shop, Alternative Automotive down here in Escondido, last year to troubleshoot my engine which resulted in finding a cracked head and going the rebuild route. My truck runs solidly well. The owner is a former dealer tech and races yota straight sixes so knows is way around our trucks. His shop did a good job on two engine rebuilds in our Beach N Toys club.

If you find you want to give troubleshooting it a shot, we can go through measuring the key sensors and see if we can understand what the ECU is trying to do and why. Hopefully that will direct next steps.

Frank

 

[jjdeneen918]

This likely wont help with mpgs but what do you mean by "factory?" The OEM tires were a P-Metric tire and if your tires are currently an LT you would need to look at load inflation tables to have the correct PSI.

e.g.

P275/70R16 = 2480 at 32 PSI / 1.1 derated P tire = 2255
LT275/70R16 = 2295 at 45 PSI (Load inflation must be equal to or greater)

So I would double what your tires are P, SL, LT etc and what the corresponding PSI is.

I’m running the Nitto Trail Grappler, 35X11.5r17. It’s a 6-ply C rated tire with a max rating of 50 PSI.

The “factory” PSI I mentioned was the door card recommendation, which I believe is 32 PSI.

So what would be the recommended PSI for this tire on our rigs?

 

[JoeCova]

I’m running the Nitto Trail Grappler, 35X11.5r17. It’s a 6-ply C rated tire with a max rating of 50 PSI.

The “factory” PSI I mentioned was the door card recommendation, which I believe is 32 PSI.

So what would be the recommended PSI for this tire on our rigs?

That would be P-metric to Flotation and it being a goofy size a lot of inflation tables wont have it, Nitto doesnt even have that size listed so I dont know. Closest on the charts would be 35-40psi..

 

[jjdeneen918]

That would be P-metric to Flotation and it being a goofy size a lot of inflation tables wont have it, Nitto doesnt even have that size listed so I dont know. Closest on the charts would be 35-40psi..

That is definitely the correct size of the tire.
I wanted a tall & ‘skinny’ tire. It was nearly the only 35” tire narrower than the standard 12.5”.

No clue on your tire terms, gonna have to google them.

Edit: tire terms.

Discount Tire | Tires and Wheels for Sale | Online & In-Person

www.americastire.com

 

[sbman]

That is definitely the correct size of the tire.
I wanted a tall & ‘skinny’ tire. It was nearly the only 35” tire narrower than the standard 12.5”.

No clue on your tire terms, gonna have to google them.

Edit: tire terms.

Discount Tire | Tires and Wheels for Sale | Online & In-Person

www.americastire.com

The load tables I have don't list that size either, so it's kind of a guess. Nitto should be able to supply the tables for their tires, I would think. Between the two sizes that it would fit into in the tables I have, I'd also guess close to 40 PSI would be appropriate. I'm surprised Costco would install oversize tires, I've never been able to buy tires from Costco because they always tell me they can only put the OEM size on it and refuse to sell me any other size.

 

[JoeCova]

I'm surprised Costco would install oversize tires, I've never been able to buy tires from Costco because they always tell me they can only put the OEM size on it and refuse to sell me any other size.

Same, I was only able to get them slightly larger on an old F250 only because the size I wanted was already mounted. So I think they can do either OEM or match what's already on it.

 

[jjdeneen918]

Tires were not sourced at Costco.

I think the only mention of Costco I made was filling tires there using their self-service air machines.

Sorry for the confusion.

 

[AK Troutbum]

Sorry if this has already been addressed, I didn't read through all the posts, but have you adjusted for the tire size in your calculations? I just went from stock size 31x10.50r15 tires in my '92 to 35x12.50r15 and no other changes to the vehicle, other than a 2" OME lift. Now for every 1 mile that my odometer shows, I'm actually traveling 1.13 miles. So, using your last example, if my odometer shows that I traveled 153 miles (burning 20.3 gallons of gas), in actuality I've traveled approx. 173 miles. So instead of only averaging 7.53mpg, I've actually averaged 8.52mpg. Obviously not a huge difference, but still over 13% difference/increase, which is something. I used to get about 250 (mixture of hwy/city), miles out of a tank of gas with the stock size tires, now I'm lucky to get 200 miles out of a tank (using my calculations).

 

[JoeCova]

Sorry if this has already been addressed, I didn't read through all the posts, but have you adjusted for the tire size in your calculations? I just went from stock size 31x10.50r15 tires in my '92 to 35x12.50r15 and no other changes to the vehicle, other than a 2" OME lift. Now for every 1 mile that my odometer shows, I'm actually traveling 1.13 miles. So, using your last example, if my odometer shows that I traveled 153 miles (burning 20.3 gallons of gas), in actuality I've traveled approx. 173 miles. So instead of only averaging 7.53mpg, I've actually averaged 8.52mpg. Obviously not a huge difference, but still over 13% difference/increase, which is something. I used to get about 250 (mixture of hwy/city), miles out of a tank of gas with the stock size tires, now I'm lucky to get 200 miles out of a tank (using my calculations).

I haven’t seen this after going to 35s my odo matches GPS almost perfectly. I'll need to retest since 13% is within a reasonable margin of error. Based on your correction math I should get 377 miles per tank and thats def not happening

 

[Broski]

I haven’t seen this after going to 35s my odo matches GPS almost perfectly. I'll need to retest since 13% is within a reasonable margin of error. Corrected I should get 377 miles per tank but im lucky to get 250

Did you not re-gear to 4.88 ?

 

[JoeCova]

Did you not re-gear to 4.88 ?

I did, I guess I need to experiment some more to see what I get. I burned 5.7 gallons of gas on an 80 mile trip but maybe it was actually 90.

 

[Broski]

I did, I guess I need to experiment some more to see what I get. I burned 5.7 gallons of gas on an 80 mile trip but maybe it was actually 90.

4.88s and 35s should put you right back to stock hearing and why your speedometer reads spot on.

 

[elripster]

So, I like many have 4.88's and 35's. I find I am about 9% undergeared with some wear on my tires. Soooooo yeah, I go less far than indicated so MPG's are actually worse but no where near 8MPG. If I am easy on it I can still get 14 on the highway. I am rarely easy on it though.

Frank

 

[elripster]

I believe 4.56's and stock put you about spot on. 4.88's and 37's get you close but 35's should leave you undergeared.

Frank

 

[Broski]

I believe 4.56's and stock put you about spot on. 4.88's and 37's get you close but 35's should leave you undergeared.

Frank

4.11s are stock
And it really depends on the tire, very few are what they say on the side wall.
But that’s another thread

 

[Devils Paw 80]

Sorry if this has already been addressed, I didn't read through all the posts, but have you adjusted for the tire size in your calculations? I just went from stock size 31x10.50r15 tires in my '92 to 35x12.50r15 and no other changes to the vehicle, other than a 2" OME lift. Now for every 1 mile that my odometer shows, I'm actually traveling 1.13 miles. So, using your last example, if my odometer shows that I traveled 153 miles (burning 20.3 gallons of gas), in actuality I've traveled approx. 173 miles. So instead of only averaging 7.53mpg, I've actually averaged 8.52mpg. Obviously not a huge difference, but still over 13% difference/increase, which is something. I used to get about 250 (mixture of hwy/city), miles out of a tank of gas with the stock size tires, now I'm lucky to get 200 miles out of a tank (using my calculations).

Reduction from 250 to 200 miles per tank is 20%, so possibly your stock tire size was 235/75r/15? I believe some FJ80s came with this size. They’re about 29 inches in diameter. (35-29)/29 would be approximately 20%. That’s a significant change.
Of course, other explanation would be that the bigger tires simply lead to worse MPG, certainly a possibly.

 

[Marvelicious]

Stock speedometer gearing may not be 100% accurate. 35/31 works out to 1.129, but comparing my gps to the CPU's speed sensor in my Torque app gives me more like 1.08, but my mileage comes out around 13-14mpg with 35s and stock gears.

 

[elripster]

Stock speedometer gearing may not be 100% accurate. 35/31 works out to 1.129, but comparing my gps to the CPU's speed sensor in my Torque app gives me more like 1.08, but my mileage comes out around 13-14mpg with 35s and stock gears.

That makes sense. To get back to MPG's, bigger more aggressive tires definitely increase road load (more rolling resistance, wind resistance, mass, and inertia) but not to the tune of 8MPG. I could get 16 when my truck was stock and I gave up 2-3MPG most of that being tires but the roof rack and other stuff adds up too.

Large tires and stock gears can mean your foot is in it so much the torque converter isn't locking up and that will also hurt in addition to the extra road load though I still don't think you should get under 10 in a 1FZE. Probably 12 is more like it. So, I don't think tires explains what the OP is seeing. I think there is something else amiss. Hopefully the shop will figure it out.

Frank

 

[AK Troutbum]

Reduction from 250 to 200 miles per tank is 20%, so possibly your stock tire size was 235/75r/15? I believe some FJ80s came with this size. They’re about 29 inches in diameter. (35-29)/29 would be approximately 20%. That’s a significant change.
Of course, other explanation would be that the bigger tires simply lead to worse MPG, certainly a possibly.

Actually, I don't know for sure what the stock tire size was that were put on them/mine in 1992, the 31x10.5 is what was on it when I bought it and they seemed to correlate with the odometer. I've only had the 35's on now for about two weeks, but I've been using it as my daily since then and I'm on my 3rd tank of gas, so the 200 miles/tank was thus far a "lucky" scenario.