Fuel Economy Changes

[Hoss 350]

I got to thinking a little about Kevin'sOffroad's posts about getting better fuel economy in his Excursion, and my reply to it.

In my reply, I stated that if anything, bigger tires would result in a net DECREASE in fuel economy, due to several different factors overcoming the benefit of the higher ratio of the tires. However, I realized that I have no direct experience with this on these trucks in particular, as both of my PS trucks had and still have the stock sized tires on them. On my older trucks, the 1989 Chevy in particular, I did notice a slight decrease in FE when I went to 33 12.5's, but it was pretty darn marginal, at best.

So, the purpose of this post is to solicit for actual experience, since I intend to upgrade to 285's on the stock rims once my current set of 265s burn up.

Did your FE change? How bad was it? I cannot imagine that the change would be ALL that discernable, but I don't know, since I haven't run them on my truck. My friends PSD seems to get similar FE to mine, and he runs 285s. Any additional info as far as pros/cons in running 285's? Do they scrub? too high ratio? (Again, I can't imagine the difference is even noticeable, but hey, I'm asking!)

 

[BIG JOE]

Heres my .02 on the tire size verses MPGs, and my exsperiences with the issue, on my 2K, DRW.

First off, I'm a ..... With an 8000 pound truck, with the Aerodinamics of a shipping crate what can you exspect... Kinda guy. But, When I bought the truck it had 215s on it, ran those about 500 miles. Got about 16 mpg. Did'nt like the Firebombs, or the 215 size. Bought a set of 235 GoodYears. Got about 16.5/17.

My thinking on this is: you'd have to drive ALOT of miles at a 1, maybe 2 mpg increase to recoupe anything if you factor in the cost of a set of bigger tires. (Especially on a DRW) And, OVER tireing anything.... you can get to a point, purdy quik, when lots of other things, >can<, go the other way.

Where I'v seen a REAL mpg gain is in opening mine up, to let it breath.... tweaking the fuel maping and squeez'n more air into it. And other things that eek more efficiency out of it.

I get a purdy consistant 17/18 mpg, 'round town, 19/20 on the highway. But thats useing Goesinta math, at the pump. The Shipping Crate applies here. I think it could be a bit better, but I have trouble controlling my right foot quite often.

When it boils down to a gravy... IF you just plain LIKE to drive one of these big 'ol things, or you have a real need to drive one... you just need to "Bite the Bullet" on MPGs. They GET, 13 to 20 Miles per Gallon. Bottom line. We can buy alot of 3/4 dollar Diesel fuel for the cost of tires & mods.

But DAMN, aint it sweet (?) drive'n one ?

JOE

 

[Mobeydick]

My mileage dropped 2 MPG going from stock to 285s on 10" Wheels. 01 7.3 F 250 4X4 CC LB Lariat. That is acounting for the 4% increase for tire size!! IE: 96 miles traveled with 285s really means you traveled 100 miles!

 

[dmd]

Biggest milage mod is to just slow down... I try to keep the TC locked, and not go over 2000 RPM. Keep it at or below 65-mph. Get almost 20MPG on the fwy. If I go 60-mph I get 21.5MPG, but it is too slow.

Pulling 10K trailer I keep it at 59 vs. 63. This gained me almost 1-MPG, which is about 9% gain.

These didnt cost a penny.

 

[SDEric]

I don't think that the aerodynamics of a shipping crate would change if you added a tire size one to two inches higher. However if you increase your tire size, if you hadn't requested it you more then likely you have increased your tire width at the time of purchase. With the increase you have a larger footprint, you are reducing your MPG. If you went taller and thinner you would retain or increase your MPG. I have not tried this yet, however logic tells me that I would get slightly 1, 2 at most, better milage.

Of course a lighter foot on the pedal also helps, as suggested before.

Just my .02

 

[KevinsOffroad]

... If you went taller and thinner you would retain or increase your MPG. I have not tried this yet, however logic tells me that I would get slightly 1, 2 at most, better mileage...

Thanks for bringing this question up in a new post, Hoss. I'm looking forward to seeing the answers. However, one thing that wasn't asked of the forum is to post their stock tire size and gear ratio. My suspicion, though maybe from inexperience, is that not everyone had our 265/75R16 with a 3.73 ratio from the factory. Would you guys mind posting your new tire size and any gear ratio changes along with your stock size and stock ratio so that Hoss (and others, myself included) can get a discernable answer as to whether our stock ratio is "right" for fuel economy, "right" for towing, or "right" for a blend of the two. I'd be willing to lose some towing torque in trade for fuel economy in the city and on the highway unloaded, as I tow my trailer less than 5% of my total driving miles.

Thanks,
Kevin

 

[Hoss 350]

Biggest milage mod is to just slow down... I try to keep the TC locked, and not go over 2000 RPM. Keep it at or below 65-mph. Get almost 20MPG on the fwy. If I go 60-mph I get 21.5MPG, but it is too slow.

Pulling 10K trailer I keep it at 59 vs. 63. This gained me almost 1-MPG, which is about 9% gain.

These didnt cost a penny.

Not trying to mod for fuel economy. I was asking what sort of changes one could expect going from the stock 265's to aftermarket 285's. To satisfy my curiosity. I am already getting 18 MPG out of my truck, without babying it one bit. THat's all I need. But it isn't worth taking a hit in FE going to bigger tires, so I wanted to know what the hit would be if I decided to do so.... Real world experience...

 

[dmd]

Not trying to mod for fuel economy. I was asking what sort of changes one could expect going from the stock 265's to aftermarket 285's. To satisfy my curiosity. I am already getting 18 MPG out of my truck, without babying it one bit. THat's all I need. But it isn't worth taking a hit in FE going to bigger tires, so I wanted to know what the hit would be if I decided to do so.... Real world experience...

Hmmm... Title of the thread seems a bit misleading then...

 

[whatabudro]

Hmmm... Title of the thread seems a bit misleading then...

So, the purpose of this post is to solicit for actual experience, since I intend to upgrade to 285's on the stock rims once my current set of 265s burn up.

Stated quite clear, intends to upgrade to 285's. he did not say "what is the best tire for FE". The purpose of the thread is to find out whether larger tires hurt fuel economy based on fact instead of assumption. I would say they have hurt my economy, but I do not calculate fuel milage very often so I have kept my mouth shut.

I just took off 265 Mud terrains and replaced with 285's this week. I got 17mpg with 265's in town last tank and will check this next tank. I don't think you can get accurate readings over one tank though. I'll post anyway just for giggles.
Budro

 

[SDEric]

After much contemplation on the tire size and fuel economy, I have come to a small realization. If you were to increase your tire height and width you really wouldn't be gaining or losing any economy. what ever you gained in height is lost to width. The height of your vehicle doesn't really matter till you are trying to put 48" tires on. but that is a whole larger subject. A few inches gained aren't going to matter about wind resistance and tire sizes are really going to matter till like I said, a much larger tire. Not a scientist, just a treeshade mechanic.

"Shipping crates weren't designed to fly" curtousy of Big Joe