Impressed with fuel mileage. Should I be? (1 Viewer)

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I'm going to throw out another theory - the gas.

My cruiser generally gets about 14 mpg. I get to around 230/240 before the low fuel light comes on. This is with 285 AT tires and low elevation. This also is my daily driving, not highway trips, so 25 mile jaunts for the most part on secondary roads. (Uncorrected mileage and well maintained vehicle)

For the last 3 or 4 tankfuls, I've been getting around 260+ before I get near the low fuel light. Exact same driving patterns. This last tankful (different gas station) is early, but looks like it looks more like the old mileage.

I would have thought it was a "winter gas" thing, but it is obviously the fall and, as far as I know, we use the same gas year around in VA. So now I'm wondering if it is ethanol content or something similar (I go to different gas stations). But I can definitively say I saw a significant change in mileage over several tankfuls with no change in driving patterns or state of tune.
 
I was running 285's on the 80, 162k miles with p0401 code, and consistently averaged 12 to 12.5. The 450 is running 275's (stockers) with 175k miles and a p0401 code.

The 80 did smell quite rich, may have been timing, I just can't believe tire size would have that much effect. Whatever it is I hope it continues.
 
I average 11.5mpg. I recently did full topend rebuild, tune up, and full emission delete. I have no added weight, 265/65/16 tires, and drive 63 and try to accelerate at a steady pace. I predict I could possibly see 15 all highway, but the best so far was 13.3. I have been tracking mileage over the last 10-12 tanks. I have new O2 sensors to install and I am going to see if they affect mileage any(I suspect they will).
 
The winter blend fuel will definitely affect gas mileage, which a lot of us as starting to see.
 
I just did a tuneup with valver cover gasket and running 295's (55psi). I get between 300 and 350 on a tank depending on speed. I drops over 70 mph fast.
 
16mpg on 275 tires...consistently in city driving...I get 300+ before the light comes on and still have 5 gallons left....stock for the most part
 
The winter blend fuel will definitely affect gas mileage, which a lot of us as starting to see.

That, and ethanol increases the octane while lowering the energy density -> lower mpg.
 
I also wonder about the correction factor.

I have 285/75/16's (33's) on my truck, and to get the correction factor, I used the roadside "odometer check" signs along the highway and over several tests determined that I have to multiply my trip meter reading by 1.08 (8%) to get my corrected mileage per tank.
 
I never get better than 15 on the freeway, 100% stock LX450. Just stepped up to 265/75/16 tires a few days ago, hoping the slightly more narrow footprint will make up for the slight increase in height.
 
I lost ~2mpg going from stock 275's to 295's. I was getting 15-17, now 13-15. My truck is up to date on all maintenance, tune ups.

I did recently advance the timing 3* from the stock NA setting, but don't really notice any difference.

I also have been running 91(premium here in CO) for 3+ years. I'm going to try 87 again to see how it likes it, but my truck has liked the higher octane. It idled better and more consistently and seemed to run smoother...
 
bone stock

Thought I'd chime in.
Original owner of a 94 bone stock with lockers, 92k miles for real.
No racks, no hitches, no sliders no nothing.....
Michelin LTX 275/70R-16's (same as original equipment).... I get and have always gotten 15-16.5 avg mpg.
Living in the NYC metro area but do 75% highway keeping close
to the posted speed limits. Keeping under 65 on a road trip gets me close to 17.
Mixing more city brings it to 15. Regular gas.
No problem.
 
I've got 4.88 gears and 35" tires. I get 12.5 most of the time on the highway. I did tow a deep hull, full windshield fishing boat to Lake Michigan and managed to still get 11.5.

My correction factor is exactly 25% more mileage more than reported on the odometer. I've checked with road markings and with GPS.

Worst tank yet was towing a (too) heavy enclosed trailer with a large four wheeler and tons of gear to Colorado. We had a 30 mph head wind and could barely drive above 60 at WOT. I aired the tires to the max and drafted semis to get up to 70.

Coincidentally, my roommate has a bone stock 80 that I borrowed for a trip. We averaged 14 :(
 
My best:
340miles per tank on 275's Michelin LTX.
320miles per tank on 285's BFG's AT's.
 
Wow, these numbers are unreal. I've never seen more than 250 miles to a tank. On stock michelens I would see between 240-250, and now running 285s I'm lucky to get 220 a tank. I'd like to l know what's wrong so I can fix it. I would be blown away to see 300, hell I'd be stoked to see 250-260.
 
I got ~340 my last tank, with 33's. I'd say 50% was socal freeway and 50% was around town babying it. I do keep it around 60mph on the free way though. If all surface streets I'll get around 290 a tank (right before filling, 270 when the light comes on). I've found that using a scangauge really helps me regulate my throttle. Oh and cruise control helps too. Oh and I use 89 octane. Probably not worth the extra money.
 

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