M0RRIS

I didn’t say it, I quoted someone. Look man, you’re not happy, bring them back to the store and tell them that. If you can’t buy new, sell these and cut your losses.

meceres

I doubt the tires will be causing that much difference. There could be a vacuum leak.

M0RRIS

I agree, some piece of info is missing. OP I’m not saying your omitting anything but I think there’s something you don’t know about. Maybe a vaccumn line got cut like Merceres said.

i went from a 275/55r20 to a 305/55r20. The weights I have down seem a little extreme and might be wrong, 43lbs to 52lbs. (EDIT: I just searched the web, they’re 43 to 59) My mileage went from 14mpg to 15.5. What I’m getting at is you kept the same size and have a huge change in mpg, I went larger and didn’t. There is an unknown variable.

Rb0553

Morris, my apologies, I see you did quote someone else. But I do appreciate the fact that it sounds like you have looked at the tires in the meantime and saw the difference in the tread design. I was of course aware of that also. But like you, I was having trouble thinking all that mpg loss could be tires. I am also going to talk to the folks I bought the tires from and see what they say. I think they do have some kind of a satisfaction guarantee. Thanks for your time and input. I have my detective work cut out for me.

new_2_trucks_guy

If you bought from Discount Tire, my experience has been that they will work with you if you are unhappy with a purchase. Other reputable dealers should as well. Lots of drivers who buy A/T tires don't give a rip about fuel mileage, so even if you've put a few thousand miles on them, the dealer should be able to resell them.

Regarding gas, you stated that you buy "cheap". Do you have a Costco membership and store nearby? They sell Top Tier gas at cheap prices. I go a little out of my way to fill at Costco about 90% of the time.

I would be in the same place you are if that happened to me. (i.e. upset) In fact, I may actually be! I've only owned my truck for a few months, same motor, 2WD and I get nowhere close to 22 mpg highway. So maybe I also need to look into more fuel efficient tires when I make my next change.

I hope you figure out the problem and come back here to share any resolutions.

Rb0553

Thanks for the reply. I will also say I had a detail done around the same time, including engine. But I have looked under the hood and see nothing out of place. Vacuum lines etc. Truck started fine and runs fine since. I did speak with the tire dealer. He is a local dealer that does the mounting etc. for Tire Rack. He matched their price so I bought from them. Nice guy I worked with there. And whether it was he was avoiding the tire issue or whatever, while on the phone he remembered my deal, but still looked it up on Tire Rack and said no to the tires being the problem, after looking over the specs right down to the fact that it wasn't a switch from LT tires to passenger tires. All that data was the same also. He also went for the gas treatment idea. But as I delve further into this debacle, I will post here and pass on the info. I am a newbie to the forum, and already appreciate the available and friendly help here. Thanks all!
p.s. When I saw what this 5.0L engine could do re mpg both in town and highway I was stoked. I actually ordered the truck from the factory because nobody had one with the equipment that I wanted, and my Wife was the Business Mgr. at Ken Grody Ford in Buena Park, Ca. I purposely ordered the last year of that current build, right before they went to the aluminum body figuring they had probably gotten all the bugs fixed. And for me, I saw the new aluminum body build as something that hadn't been tried and true yet. Yeah I missed out on some goodies, but have been very happy with the truck so far...well..that is until this.

diegoo.jayjay

22 mpg???? I'm gonna say that's alot honestly. 16 sounds more realistic but if that drop is true, you shouldn't have seen that. Especially with CA going to summer gas.

Check everything at this point. Battery, spark plugs, maybe a hanging brake caliper?? The other day I found a hay string wrapped around my brakes, so you never know.
Brakes are the only thing I could think of that dropped you that much significantly.

M0RRIS

I hit 22/23mpg on a road trip across Michigan when I was stock.

Rb0553

Yeah...Morris has got the same basic drive train setup as I do. And the long distance freeway thing, especially with some down hills in it, yup I did get 21-22. I wouldn't say it was there all the time on these trips. But it would certainly be there for a lot of my trip. But then....it happened....WAAAHHHH this last trip I almost made it to 17 a few times.

joedotmac

What you've got is probably a combination of things that are all adding up to your total loss. If the only change associated with the symptom is the tires, then it's the tires.

In the performance world it's generally understood that unsprung weight is a factor x10 the amount of sprung weight. Unsprung would be wheels/tires, hubs, control arms, axles and the like.

A 2 lb increase in tire weight (unsprung) is like carrying an extra 80 lbs in the bed of your truck.

There's going to be additional negative impact due to bringing the heavier rotational mass up to speed, this will require more work (torque) to bring to equal speed of the lighter tire. Now this is marginal at best, but is a factor. Tread pattern will also be factor.

Tirerack dot com has pretty good specifications on most all tires to compare and contrast weight, tread width, total width and the like.

Many tire manufactures offer ECO branded tires, simply it's a combination of light weight, tread pattern, and tire compound that provide the mileage difference over the non-ECO tire. So the tires alone can certainly make a change in observed efficiency.

Again probably more than one contributing factor the tire change has incurred to the current drop in MPG.