cat mpg opinions and advice

**droy** · 11.07.2009

Originally Posted by Jfaulk99

On a side note while it may be "proven" that 22.5LP get bet better fuel mileage. (not sure what the actual improvement would be, mpg wise) they also make about 31 more revolutions per mile than a full size 24.5 which means they will wear out sooner. So without doing any real experiments or hard math I'd say if you take any fuel mileage improvements and subtract the tire wear it may kill any advantage. BUT 22.5's are cheaper BUT they have a lower weight rating if you haul heavy, I blew 2 and gave up on them. It definitely wouldn't be worth buying new wheels and tires just for a fraction of MPG improvement.

I tend to agree with you on the "wear out sooner" point, but am going to paraphrase something I read awhile back; it just doesn't make sense.
Taken from Heavy Duty Trucking, out of an article on "specing trucks for fuel mileage". A rep from a major tire manufacturer stated that "due to the compound put in the smaller diameter and lo- profile tires, there is not a lot of difference in the tread life of a 22.5 tire compared to a 24.5", he also stated that the difference in tire replacement cost was less a factor than brand/type of tire and price shopping.
Although I DO believe that two identical trucks, one with 24.5, & one with 22.5, run for, say a million miles, the 22.5 equipped truck will cost less to run, (tires & fuel). Less rolling resistance = better MPG; and cheaper purchase price for the smaller tire. I have a hard time using what the tire rep said as part of my argument. If the compound of the smaller tire lets it get almost the mileage of the taller tire, why not put that same compound in the taller tires?
If there is truth in this, could the reason be the fact that large fleets use the small tires, and evil O/Os use the biguns?

**swaan** · 11.07.2009

The parts guy at cat told me that they are out of stock on the remans (10r7155) , so if i order a reman i will most likely get new(130-9710).
Your prices are better then i could get, I was quoted 1338 for reman plus 791 for core. Or $2359 for new. Keep in mind this is canadian.

**SpeedRacer** · 11.07.2009

Originally Posted by droy

I tend to agree with you on the "wear out sooner" point, but am going to paraphrase something I read awhile back; it just doesn't make sense.
Taken from Heavy Duty Trucking, out of an article on "specing trucks for fuel mileage". A rep from a major tire manufacturer stated that "due to the compound put in the smaller diameter and lo- profile tires, there is not a lot of difference in the tread life of a 22.5 tire compared to a 24.5", he also stated that the difference in tire replacement cost was less a factor than brand/type of tire and price shopping.
Although I DO believe that two identical trucks, one with 24.5, & one with 22.5, run for, say a million miles, the 22.5 equipped truck will cost less to run, (tires & fuel). Less rolling resistance = better MPG; and cheaper purchase price for the smaller tire. I have a hard time using what the tire rep said as part of my argument. If the compound of the smaller tire lets it get almost the mileage of the taller tire, why not put that same compound in the taller tires?
If there is truth in this, could the reason be the fact that large fleets use the small tires, and evil O/Os use the biguns?

It probably has something to do with the LP tires having less flex (hence rougher ride) and the taller tires need a different compound to make them wear right with the flexing. Just a guess. I agree with your reasoning though, it definitely makes since to order a spec'd right for 22.5's if you can, otherwise run what ya got. I think it's more important to have it spec'd right for whatever tires you have, but ideal if you can spec right with 22.5LP.

Mr. Haney, any reason for me to think about a cam upgrade in the 6NZ down the road? Or just better keep it stock and run the 58 injectors and upgraded turbo/ecm?

**Mr. Haney** · 11.08.2009

Originally Posted by SpeedRacer

Mr. Haney, any reason for me to think about a cam upgrade in the 6NZ down the road? Or just better keep it stock and run the 58 injectors and upgraded turbo/ecm?

I like the cam upgrade, because I find that the soot level drops in the oil. This tells me that more air is making it into the cylinder for a better combustion cycle. I also see about a 1/2mpg increase in fuel mileage with the cam I recommended. I've never had anybody I know use the 130-9710 cam to get feedback from. I've been told this cam is worth 50 Hp on a chassis dyno and doesn't create a lopey idle when used with larger injectors.

**smokin809** · 11.08.2009

Originally Posted by Mr. Haney

I like the cam upgrade, because I find that the soot level drops in the oil. This tells me that more air is making it into the cylinder for a better combustion cycle. I also see about a 1/2mpg increase in fuel mileage with the cam I recommended. I've never had anybody I know use the 130-9710 cam to get feedback from. I've been told this cam is worth 50 Hp on a chassis dyno and doesn't create a lopey idle when used with larger injectors.

Mr haney is bang on with his cam selection, i've gained near 1/2 mpg, and soot is down according to my spinner.

**SpeedRacer** · 11.08.2009

Originally Posted by smokin809

Mr haney is bang on with his cam selection, i've gained near 1/2 mpg, and soot is down according to my spinner.

My soot runs 0.4 now on my samples running the Gulf Coast Filter. I don't know if I'll go much lower. If I was to reduce soot though, I may be able to extend my change intervals out even farther.

I'm definitely going to keep my eye on the soot as I make any changes. Oils samples are invaluable, and I swear by the GCF.

**droy** · 11.09.2009

Originally Posted by swaan

The parts guy at cat told me that they are out of stock on the remans (10r7155) , so if i order a reman i will most likely get new(130-9710).
Your prices are better then i could get, I was quoted 1338 for reman plus 791 for core. Or $2359 for new. Keep in mind this is canadian.

I am totally ignorant about the American dollar / Canadian dollar thing, and am sure that if it was good economics, all you guys north of the fence would be doing it; but what about ordering the cam from the main store in Peoria, IL? Does shipping and tariffs kill any savings, or is it the dollar exchange thing, or maybe a combination?
My price, with sales tax for the cam and core was $1764.81; almost $600.00 less than your quote. A nice chunk of change, no matter what country you're in.

**droy** · 11.09.2009

Originally Posted by Mr. Haney

I like the cam upgrade, because I find that the soot level drops in the oil. This tells me that more air is making it into the cylinder for a better combustion cycle. I also see about a 1/2mpg increase in fuel mileage with the cam I recommended. I've never had anybody I know use the 130-9710 cam to get feedback from. I've been told this cam is worth 50 Hp on a chassis dyno and doesn't create a lopey idle when used with larger injectors.

As I stated earlier, I feel the cam replacement had a lot to do with my increase in MPG; but because of other mods, (like the new flash file in my ecm), the turbo, etc, I am sure the cam replacement is not solely responsible.
Had another injector replaced last week; #3 had went out, apparently not all at once. My mileage had dropped to a low of mid 5, to a high of 5.9, and really couldn't hear a engine miss. I figured this was due to the water in fuel problem our terminal was fighting. After replacing the bad injector, I made two trips,
(1) Lake Charles, LA to Waxahachie, TX
(2) Lake Charles to Valdosta, GA.
Three fill ups for the two trips gave me 6.07, 6.19, and 6.39; (average of 6.2166). Yes, I'm aware it was mostly flatland running, and just three fill ups, but after seeing averages of 4.8-5.0 when I first purchased the truck, the grin on my face as I put up the calculator shows how I feel about the work done to my engine, and the added power is a big bonus.

**haystack** · 11.09.2009

Blakesreman.com out of denver is showing an exchange price of 650 for the pn 10r7155

**C16KIWI** · 11.09.2009

I am also very interested in doing a cam change looking in my service manual the C-15,C-16 and the C-18 with part number 201-2677 all have a exhaust lobe of 8.515mm and the C-15 and C-18 have the same inlet of 9.702mm with the C-16 being 9.431mm.
Injector lobes are all much the same C-15 10.471mm,C-16 10.451mm, C-18 10.451mm.

My question is the only difference must be the duration how do you find this out????