Realistic mpg's

Havvkeye · December 21, 2016

And the tires look flat when they're that low. Max psi is 50 and never had any problem keeping them between 42 and 45.

You really think running 13psi over the recommended is better? 5psi below the MAXIMUM does not leave much room for increased psi from driving. 32psi always looked and rode fine for me when I had the stock tires on. I only run around 45psi in my oversized LT tires where the max is 60 (because that is what the tire manufacturer recommends)

edit: For the OP, I have seen ~3mpg drop from the winter gas mix alone this year and I still get ~13mpg with my heavier tires, front level and a lead foot.

sdeeter19555 · December 21, 2016

You really think running 13psi over the recommended is better? 5psi below the MAXIMUM does not leave much room for increased psi from driving. 32psi always looked and rode fine for me when I had the stock tires on. I only run around 45psi in my oversized LT tires where the max is 60 (because that is what the tire manufacturer recommends)

edit: For the OP, I have seen ~3mpg drop from the winter gas mix alone this year and I still get ~13mpg with my heavier tires, front level and a lead foot.

The maximum is cold inflation, which accounts for the tire heating up and the pressure increasing accordingly...

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gr8almty1 · December 21, 2016

2015 LTZ Crew cab. Standard Bed. 22" stock tires, wheels, and air.

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Havvkeye · December 21, 2016

The maximum is cold inflation, which accounts for the tire heating up and the pressure increasing accordingly...

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That is interesting... seems like it leaves a lot of room for variability. Wonder what PSI it tests at for a true max then...

sdeeter19555 · December 21, 2016

Yup, tires aren't that sophisticated.

The guy I worked with got tired of filling this woman's leaky tire every night, pump a standard old car tire up to 100 psi and it held. Most have a "not to exceed" for seating beads...

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SouthernSilveradoGuy85 · December 21, 2016

I've also always had trucks with nice sidewalls, none of that low pro crap. So 32-35 psi makes the tires look flat with a big bulge at the bottom. Then imagine putting a decent amount of weight in the bed. I just found having it between 42 and 45 seems to be the sweet spot for me. Gives a good enough ride and doesn't seem low. I've never had the psi go over 48 after driving even in the summer on a long trim and never had wear problems running that range of psi. So ya 35 just seems low to me for a full size truck. It might work on a low profile tire since the sidewall is probably more stiff and doesn't bulge, but just seems like the more sidewall you have on a heavy truck the more psi you can and should run. Even on a passenger rated tire.

beertestr · December 21, 2016

I had a 15 Yukon XL 5.3 4wd and tow package (3.42) for 14 months and 33k miles. Daily commute is 18 miles each way, 4 miles highway, 14 miles 45mph Blvd and city stop/go. Regular mpg was 17-18, highway was 20mpg or higher. Winter was lower, remote start can drop mpgs a lot with relatively short drives. 8-10 min idling (0mpg) and a 35 min drive (17-19 mpg)....

Food for thought. A fully warmed up 5.3l, according to the CAN data idles at 6-6.5g/s airflow. That's fully warmed up, no AC load. AC cycles on with defrost, and cold engines have higher friction, so this is likely the lowest air flow rate. Assume the engine is running stoichiometric, so divide the 6 grams/s airflow by 14.7 to get fuel flow rate per second. A few other calculations later, and converting to gallons, and idling 5.3 consumes about a quart of fuel per hour.... Minimum. It adds up, doesn't it?

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Rolling Thunder · December 21, 2016

Tire makers and auto makers spend millions on research, testing and engineering to the point that they paste a sticker on every vehicle with the recommended OEM tire pressure, tire makers also post recommended tire pressures when they are newly bought as repl;acements, and guys here essentially tell them all indirectly they are full of $hit by running absurd tire pressures on their own without a lick of engineering evidence. Is it me lacking common sense or is this the trend today?

Does everyone have their speedos adjusted when tire sizes are changed?

SouthernSilveradoGuy85 · December 21, 2016

Tire makers and auto makers spend millions on research, testing and engineering to the point that they paste a sticker on every vehicle with the recommended OEM tire pressure, tire makers also post recommended tire pressures when they are newly bought as repl;acements, and guys here essentially tell them all indirectly they are full of $hit by running absurd tire pressures on their own without a lick of engineering evidence. Is it me lacking common sense or is this the trend today?

Does everyone have their speedos adjusted when tire sizes are changed?

People also mod their cars, trucks and motorcycles everyday to change what the engineers designed so it's really not that big of a deal to run the psi that you want to run as long as it's safe. I've ran 42-45 psi for years with different tires and guess what, 0 problems with wear and no tire blowouts. With a tire with actual sidewall that's not low pro psi between 32 and 35 just seems low for the tire. There's a huge bulge at the contact patch and to me that seems like over time it may even weaken the sidewall. I'd probably prefer high psi over low psi.

But hell, I'm usually wrong so it's probably a hazard to follow any of my advice.

sdeeter19555 · December 22, 2016

I go the other way...calls for 60 front and 70 rear...run 55 all four corners, tires wear perfect and it rides well.

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Pearl2017 · December 22, 2016

I must agree also, Been running ~42psi on every vehicle I own for many years without a problem. If you want mileage it definately helps. Also most tires go down over time too so if you are at 31 and it goes low the sidewall can overheat from flexing and blow out. A guy I once worked with did that one even after i pointed out how low it looked.

Cowpie · December 22, 2016

Tire makers and auto makers spend millions on research, testing and engineering to the point that they paste a sticker on every vehicle with the recommended OEM tire pressure, tire makers also post recommended tire pressures when they are newly bought as repl;acements, and guys here essentially tell them all indirectly they are full of $hit by running absurd tire pressures on their own without a lick of engineering evidence. Is it me lacking common sense or is this the trend today?

Does everyone have their speedos adjusted when tire sizes are changed?

Well, there is some truth there, but it also applies only to the tires that came as stock from the OEM. Once you change brand, tire, rating, etc and the sticker in the door quite possibly is inaccurate. And the vehicle OEM really doesn't do any R&D regarding tires. Tire makers do the bulk of the R&D. Auto makers figure out what tire specs are needed and get bids from tire makers to supply them. Not always the "best" tire for the vehicle or what it is used for.

But in keeping with your line of reasoning, do like I did.... get on the the tire brand website and do the contact page thing. Ask them for a load pressure chart on your particular tires. DO NOT STATE what you have them on! Else they will punt to the OEM. If you state the tire only, they will give you a chart that shows the proper tire pressure for the loading on the tire. I got this from BFG a while back when I changed from stock Michelin to KO2's on my pickup. Moved up one size on tires at the same time. Tire maker Recommended tire pressures not close to OEM sticker. But then, the OEM doesn't make tires, BFG does. And I follow load charts religiously in my commercial heavy trucks. Probably why I got 447,000 mile out of my last set of drive tires on my semi and still had 8-9/32 tread left and no uneven wear.

I didn't have my speedo adjusted when I went up one size in tires. Actually the speedo was off by about 1 mph (faster than I was actually going) and the new tires brought it dead on.

Havvkeye · December 22, 2016

Does everyone have their speedos adjusted when tire sizes are changed?

My very scientific experimentation (driving by police speed signs) tells me that I am about spot on in terms of speed with my 305/55R20

Rolling Thunder · December 22, 2016

My very scientific experimentation (driving by police speed signs) tells me that I am about spot on in terms of speed with my 305/55R20

If your 305/55 R20 tires replaced an OEM 275/55 R20 then your speedo is 4.1% off and you're screwing yourself out of 1440 miles of a 36,000 mile warranty..

https://tiresize.com/comparison/

Andy Seibel · December 22, 2016

I've also always had trucks with nice sidewalls, none of that low pro crap. So 32-35 psi makes the tires look flat with a big bulge at the bottom. Then imagine putting a decent amount of weight in the bed. I just found having it between 42 and 45 seems to be the sweet spot for me. Gives a good enough ride and doesn't seem low. I've never had the psi go over 48 after driving even in the summer on a long trim and never had wear problems running that range of psi. So ya 35 just seems low to me for a full size truck. It might work on a low profile tire since the sidewall is probably more stiff and doesn't bulge, but just seems like the more sidewall you have on a heavy truck the more psi you can and should run. Even on a passenger rated tire.

The psi rating on the door jamb is for the factory tire size based on the weight of the vehicle. If you put 10+ psi above that number I bet your ride is quite bouncy. Now if you drive around with an extra 1000 lbs of sand in the bed for winter, it might ride fine.

There are so many variables that change when you change the tires, that you should do as cowpie stated and get the load charts from the tire manufacturer. But if you stick with the same load rating and size that GM put on your truck, there's no reason to go overboard and overinflate your tires. I bet the center of your tread is wearing off.....

Anyway, I average around 20 mpg highway to 17 mpg city.