Extremely Poor Gas Mileage Troubleshooting

[rtr2000]

I recently purchased a 2013 Silverado 1500 LTZ 5.3 crew cab and am averaging 13.6mpg. I understand it's a truck, but I figured it wouldnt be that terrible. I use cruise control and coast as much as possible, but still have the poor mileage. It has 117,000 miles on it. I have 33x12R20LT Trac Grip M/T Thunderer tires and XD series wheels. I feel like I should be getting better gas mileage than this. Suggestions?

[richard wysong]

put it up on a lift and make sure there's not a brake dragging or any major resistance in the driveline in neutral, if it's 4wd make sure the front axle is disengaged and the transfer case isn't in 4wd, when were the sparkplugs last changed,air filter, clean the MAF, at that mileage the O2 sensors may be getting lazy and are due to be changed, make sure you buy them from a reputable supplier, there's a lot of counterfeit crap out there even at Rockauto. Scan it for soft codes that won't set the CEL, check your tire pressures and go 5psi over what it says on the door. Are you sure the odometer is accurate with those tires?

[richard wysong]

I wouldn't expect more than17-18 mpg in  mixed driving, low 20s hiway, my Caddy only gets 13 in town but 25 hiway

[rtr2000]

Had a tune up at 115,000 miles. I just replaced an O2 sensor on the passenger side two weeks ago. I am not sure if the odometer is correct with the tires. Is there a way to make sure the speedometer/odometer are correct without having to pay a lot of money to get it checked? Also, my oil pressure is reading low, but I dont have any leaks and I recently replaced the Oil sending unit with AC delco and its still reading low. Do you think I could have an electric problem that's causing that issue and also causing me to use too much fuel?

[rtr2000]

Also, do you think that a cold air intake might help it?

[Robertabf]

I think the culprit is the higher ethanol content allowed because of higher prices...My mileage is down as well

[richard wysong]

Save your $, cold air intakes are more for show, the factory system is CIA and designed for maximum efficentcy

[richard wysong]

Robert may be right. if you have a scan tool look at the fuel trim numbers and that will tell you if everything is working as it should

[richard wysong]

as far as checking the odometer/ speedo you can do it with your phone, some1 explained how in 1 of the posts not long ago but I don't remember the procedure

[CamGTP]

Remove your heavy tires and watch the mileage climb back up.

 

12-12.5 wide tires will eat away at fuel mileage. And if they are mud terrains with huge lugs for tread, forget about fuel mileage.

 

I bet you are at least 40lbs heavier per corner than a stock wheel/tire combo. Those 33's probably weight 60-70lbs each and the aftermarket rims can be heavy as well. Stock 20's in a non load range E are only 40-43lbs for most tires.

Edited July 16, 2022 by CamGTP

[rtr2000]

23 minutes ago, CamGTP said:

Remove your heavy tires and watch the mileage climb back up.

 

12-12.5 wide tires will eat away at fuel mileage. And if they are mud terrains with huge lugs for tread, forget about fuel mileage.

 

I bet you are at least 40lbs heavier per corner than a stock wheel/tire combo. Those 33's probably weight 60-70lbs each and the aftermarket rims can be heavy as well. Stock 20's in a non load range E are only 40-43lbs for most tires.

What are some good options for tires that are larger and look "aggressive" but wont kill mileage. I honestly dont care too much about the aggressiveness of the look, i just like the ride height im at now and dont want to downsize for that reason

[CamGTP]

Going with 33's isn't a big deal, so you are fine going with that size again.

 

Just don't get mud terrains and don't buy load range E tires that are super heavy.

 

The new stock size for 20's are 275/60/20 on 2019+ trucks, those are 33in straight from the factory. They are 1.4 inches narrower than the current 33's you have and way lighter.

 

Toyo Open Country AT3, Falken Widepeak AT's, Nitto Terra Grapplers and many more tires will all come in that size.

 

Going to a 285/60 or even a 305/55/20 pretty much only gives you LT tire options and those are load range E and much heavier and cost a lot more.

[CamGTP]

Just for giggles I googled that tire you have, they are actually a load range F in a 33x12.5/20. That's a lot more beef than a 10 ply load range E tire.

 

I couldn't find an exact weight of that tire but it's for sure over 60lbs. Then I looked up a Toyo Open Country in a standard load rating and they are only 45lbs each. Figure you'll save roughly 20lbs per corner just in tire weight going to a different tire and with less width the contact patch the truck will work less to do the same thing.

[richard wysong]

on your op problem it may be the oring on the pickup tube to the oil pump DIYR has done extensive posts on the fix

[Jworks]

You've got some good suggestions above in these posts.  I'm no expert but the tires came to my mind first thing.  I have just regular street tires (Continental) on my 4x4 and I get 20-21mpg on the hwy on a long trip.  Same engine but 2011 model truck. Local driving I get 17mpg.