12.2 mpg unloaded driving like a granny

Alaskanpeeps · Aug 3, 2016

I have a 2013 ccsb 4x4 hemi 42k miles. Hand calculated I get 12.2 mpg around town. When I bought the truck I had 265/70/17s and was geting 16mpg around town. Things I have changed.... Sport 20s, 305/50/20 Toyo At's, Mcqaughys 2" springs, spark plugs, redline oil. K&n drop in filter. I run 90 octane because I can't get 89. It's 87 or 90. This doesn't seem right so I wanted opinions. It's nothing I can't live with. But is there anything I can do to get a lil better mpg? T

Ram444 · Aug 3, 2016

Did you have the speedometer recalibrated or is the tires the same OD as the OE equipment??

Alaskanpeeps · Aug 3, 2016

Stock tire is 31.6 new tire is 32. I didn't think that was a big enough difference to bother with. But maybe that's where it's at?

Ram444 · Aug 3, 2016

Alaskanpeeps said:
Stock tire is 31.6 new tire is 32. I didn't think that was a big enough difference to bother with. But maybe that's where it's at?

Nope but it is a little wider too which would increase the rolling resistance. That's a pretty significant drop in mpg. Did you by chance add an after market exhaust? I once had a custom exhaust builder build me a not so custom exhaust. My mileage dropped like yours right after the exhaust was put on. I had him cut off the exhaust and found it was narrowed to 1.5" in one spot.

drittal · Aug 3, 2016

Unsprung mass also inreased. I'm guessing a more aggressive tread pattern as well.

Could be something else too, but bigger wheels and tires with more aggressive tread aren't helping mileage.

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sbuko213 · Aug 3, 2016

That tire is wider, causing more rolling resistance. If you have a tuner you can most likely adjust this.

Alaskanpeeps · Aug 3, 2016

Stock exhaust, new manifold studs, no tuner. Tires are 1lb lighter. Idk the weights on stock aluminum 17s verses stock sport 20s. What about this injector flush the dealer tried sailing me? I use a can of sea foam every couple months

Ram444 · Aug 3, 2016

Well that sucks. You can swap out your differentials/transfer case with full synthetic might help??? Last question, does your exhaust have some black smoke if you rev it up or soot on the paint near the exhaust exit. If so, you could pull one of your plugs to see what it looks like.

Alaskanpeeps · Aug 3, 2016

No black smoke or soot. Changed plugs 2k ago. I thought 30k plug change was crazy but at 40k I was getting 8 to 9 mpg and check engine light came on with a cylinder 5 misfire. That's what got me chasing mpg. Plugs, filter and oil change at 40k. I'll change trans/diff fluid and I guess it is what it is. After all I didn't buy a truck for the great mpg. Thank you for ur thoughts.

TRCM · Aug 3, 2016

That's about all I get in mine around town....but then again my around town driving is like 30 miles of stopping and going every 1/8 mile.

But on the highway, I am upwards of 22 mpg.

and yes, that is hand calculated.

atc06jh · Aug 3, 2016

your rolling friction can be calculated at .02. If that helps. (only people that work crashes will get that!)

jasonw · Aug 3, 2016

What spark plugs did you use?

freefallin · Aug 3, 2016

I'm completely stock with ~900 miles. Hand calculated at 11.3 mpg, mostly city driving pumping 89. The 3/4 ton with the CTD was averaging 14.5 mostly city, also hand calculated, but that was after 12k miles. When new, she was at 11-12 mpg. I'm hoping the mpg's will improve a bit after break-in and first oil change.

Treburkulosis · Aug 3, 2016

I'm getting a little over 14 right now with a small load in the bed. It's about 1 mpg better. I'm a 12 2wd hemi.

Alaskanpeeps · Aug 4, 2016

atc06jh said:
your rolling friction can be calculated at .02. If that helps. (only people that work crashes will get that!)

Calculating rolling friction! Yep no clue lol

jasonw said:
What spark plugs did you use?

Ngk 92174 lzfr5c-11 stock plugs for 2013 to b replaced every 30k

from some of you that posted your mpg. It looks like I'm not doing to bad. I've just seen quite a few people comment on other threads that there getting 14 to 16 mpg and runing 35s. That must be high way miles. And though I was getting 16 new there are some variables to consider. I appreciate ur feed back thx

6.7CumminsDrvr · Aug 4, 2016

I get around 13ish "city" driving on my current setup.

tmletourneau · Aug 4, 2016

I get around 13 in town with mine as well, 2016 CCSB 1500 Hemi.

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Hemi395 · Aug 4, 2016

drittal said:
Unsprung mass also inreased. I'm guessing a more aggressive tread pattern as well.

^^This. I went from the stock GY SRA's to the Cooper Discoverer AT3s in the stock 275/60/20 size and lost 1.5-2MPG just from the tread pattern and added weight of an AT tire.

14hemiexpress · Aug 4, 2016

I don't think your far off honestly city driving is a killer for the hemi city driving. The wider tires don't help.

Treburkulosis · Aug 4, 2016

Rams were never known for good mpg. You pretty much know that going in. My dad had a 00 ram 5.9 it got maybe 9mpg. A 03 4.7 ram that got 12 mpg and then my 12 hemi seems to stay between 12 and 14 mpg no matter what. I like my ram for the on tap power, the ride is nice, and the seats are comfortable. It also can haul pretty much whatever I throw at it. You have to sacrifice somewhere. You can never have the best of both world's.

12.2 mpg unloaded driving like a granny

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