Yeah, I understand the 3.73 vs 4.30 has been debated here so much that it's like kicking a dead horse. But I have searched the forum and cannot seem to get my question and am looking for someone with the exact setup. Long and skinny, I am looking for real world towing and MPG experiences with someone who is running the 2017-2019 F-250 with a 285/75r18 AT. I am wanting to run this set up as I already have tires, snow chains for this size and don't need or want a full size 35" tire. However, gearing is another such decision I need to address before placing an order and since I am going to a gasser, 4.30 seems like it would be the correct solution for this set up. However, the 285/75r18 comes out to 34.8 where the factor 20's come to about 34.2 or so and the 3.73 might net me better highway MPG's. I do understand that we do not buy these large beasts for mpg's, however I would like get a guess as to what to expect. Most of my driving is rural backroads (empty) and the occasional highway road trip (few hundred finds in the bed) at usually no more than 70 mph. Towing is limited to 7-9K around twice per year and that is for hunting. Does anyone else have a similar tire set up that can chime in?

 

I don't have that set up but you don't need to think about 4.30 gearing until your choose to get 37's.

 

My worry is that by putting a plus size tire that is will kill the performance of the 6.2. Even with a 4.30, a 285/75r18 should bring the actual ration down to a 4.09 where is the same size would bring the 3.73 to a 3.55. I run 90% of the time on flat or rolling hills but the other 10% is in the mountains and have zero intentions of ever going to larger rubber.

 

i ran that size toyo at2s on my 2014 3.73 and averaged 14 unloaded 2 lane roads. my 17 with 4.30s gets 10 on small factory tires.

 

 

I have this exact combo, 2018 F250, 4.30, 285/75r18 AT tires. Biggest factor seems to be speed, drove from MN to FLA few weeks ago and got 13.7 whole trip, driving a steady 70 mph or so. If i drop speed to 55-60 mph will easily exceed 15.5 mpg. Pulled our 13K lbs 5ver 3800 miles over Xmas over the Blue Ridge/ Smokies got 7.5 overall, often driving 65-75 mph. For me the 4.30 was a must, as pulling 5ver is main purpose..

 

Upon first taking delivery of my '17 F-250, I installed the 285/75R18 Toyo ATII Extremes, as I purposely ordered the 4.30 gearset to offset the tire size I wanted to run. After a season of tugging our 5'ver (~10,500#) around through the BC Rockies, I subsequently went back down a size to 275/70R18 at the start of this winter. While I did see a MPG increase (1-2) after the switch, my primary rationale was for towing and to avoid dropping to 2nd gear on some of the bigger pulls. It would almost hold 3rd, but once it fell out of the meat of the torque curve, I knew 2nd gear was coming. My decision was made even easier by wanting to run all-weather rated all-terrains, as understandably the Toyo's performed poorly in frigid temps. Lastly, I fully admit I did not pay attention to the weight of the Toyo's prior, but after going through this experience, it is something I am cognizant of now. Hope that helps FWIW.

 

 

Just do it and don't worry about it! I have that size in the ridge grapplers with 3.73s and still have plenty of power. I just sold my camper but it was 7400lbs dry and after adding the tires my truck still pulled it fine on the interstate. Lately I have been averaging around 13mpg could get better if I tried.

 

I couldn't imagine owning a gasser without 4:30's even with the stock 18's (which I have). I would think 35 inch tires would be the perfect combination. At least that is what I plan on adding when the stockers wear out.

 

Thats is what I am concerned with mostly. I really like the 285/75r18's but am worried about running empty at 70 mph on the highway with 4.30's. Granted oversized tires is about the worst thing you can to for mileage.

 

I would think a 35 inch tire would put the 6.2 and the 4:30's in the sweet spot at 70 mph and that is roughly 2,000 rpms. Perhaps someone with that combo will add to the conversation?

 

I have a stock 6.2 with 373`s and the factory tires at which measure 34.5 inches on the stock 20 inch rims. I think its perfect, At 75 mph rpm`s are 2000 and it can get 17 mpg all day long on the highway with the bed loaded with gear.

When i tow its usually not more than 8000lbs which is not hard for these trucks. I wouldn't even think about 430`s unless i was towing everyday as a work truck or planning on 37`s. For the average guy 373`s will give you the best fuel milage and still offer plenty of towing power

 

Where you drive is also important. I live in CO and tow over 11,000' passes. Altitude takes ~3% per 1,000' from normally aspirated engines. So, where I live/tow, I'm losing 20-30% of my power. So, I'd hedge by grabbing the largest numeric gears I could. If I were shopping for a 6.2 SD, I'd grab the 4.30.

If I lived in South Carolina, I may consider dropping down to the 3.73.