n2moto

I drive 80 mph when at all possible. I don't do it if I have to weave or drive like an edit but I drive 80. The overhead says 17.4 to 17.6. So I just sold my first born and filled up my truck and reset my overhead. I made myself drive 1800 rpm or about 62 mph. My overhead now reads 21.4 to 21.7 mpg. I know I didn't do it by hand but I know my routes and that's the number.

I need taller tires! I'm going to go 33's I think that should get me close to 75and not exceed 2K. NV5600 and 3.73 rear.

Does that sound about right or am I on drugs?

P.J

Yes, drugs.

Larger (heavier,wider, even though taller) tires will almost certainly cause you a net LOSS in MPG's.

n2moto

I've heard that and I could see it doing stop and go driving but.... I don't do much of that. I'm not looking for wider yes they will be heavier. Doesn't the fly wheel take effect when on the hiway? I don't recall the difference when I put them on my 97 but I don't remember the mileage going down. It was quieter cruising down the road with lower RPMs. I think spinning these motors kills your mileage worse than taller tires.

Fortuneatly my tires are in great shape so I don't have to buy any soon. Unfortuneatly my tires are in great shape so I don't get to upgrade any time soon.

MikeyB

I'm turning right at 2k rpms at 70mph with the 285's. I didn't see a gain by going to the larger tire, but at least I didn't loose any.

MikeyB

BlackSunShyne

I saw a gain going to a taller tire(the 35 vs. stock BFG tire). I do have 4.10s tho...

n2moto

Mike do you remember how much it dropped your RPM? If you can keep the same speed not loose any mileage and drop your RPM then that is a good thing in my book.

PRO-NRA

I went from the stock 285 to 37X12.50 just to lower my RPM on a short geared G56 expecting a penalty on MPG. To my surprise, I picked up about .5MPG on the highway. IMO, you will lose some on city driving but if you drive mostly highway you will probably gain a slight MPG or at least a wash but you will be spinning the engine slower therefore less noise and maybe wear? My $0.02.

MikeyB

It was about 100 rpms. My speedometer was off with the stock 265's (2 mph slower than indicated) so there's a slight change due to that. With the 285's the speedometer is dead on using the GPS.

MikeyB

n2moto

Don't the 04.5 have the third or second injection event? If that is the case spinning it slower should help? I'm guessing and really don't know what I'm talking about. If somebody does please chime in.

snoyes

RPM drop is one thing, but in order to get there, with the bigger tire, you raise the truck up increasing the drag on the truck. At 80 MPH, while you will drop RPMs with the bigger tires, the drag at that speed will most likely negate alot of the good the lower RPMs give you. So, 62 MPH gives you good mileage not only based on RPM but also the decreased drag on the vehicle at that slower speed.

2003Ram

No gain or loss going from 265s to 285s for me.

2003Ram

You have to account for the wind resistance factor as well. You'll find the (mileage) sweet spot somewhere between 65 and 70 with your new tires.

dozer12216

The sweet spot is "The slower - the sweeter" if you manage the throttle playing with economy in mind.

n2moto

I understand slower is sweeter when mileage counts. I travel hundreds of miles on a weekend doing my hobby. The difference between 65 and 80 can be an hour or more. When I make the longer trips it is 3 or more hours. Ok on the long trips I'm running harder.

Lower rpms higher mph, I don't expect higher mpg but a quieter motor and the same mileage would be nice. Around town slower with taller I think will improve the mpg.

I've started tracking my fill ups so I'll know.

Thanks all for your input. When I burn through these biscuits I'm going to 33" tall and I'll post my results.

mmurray

Traveling @ 80 going from 265 stockers to 35" Toyo MT's I lost about 3.5 mpg's....

Slowing down to what ever the posted speed limit is (i.e. 55, 65, 70 on most major highways) has gained about 2.5 mgp's back...

265 Stockers: @ 80 overhead (22.5mpg), Hand Calc (17.5mpg)
@ 60 (who knows? diesel was relatively cheap back then! hahahaha)

35" Toyo MT's: @ 80 overhead (19.8mpg), Hand Calc (14mpg)
@ Posted Speed Limit, overhead (20.3mpg), Hand Calc 18mpg)