3126b mpg ??

[bigdog]

I have a Tradewinds 7390 LTC with 91K on it and have had it for 5 months now and am getting between 6.5 and 7.5 mpg. I am running around 25,500# and pulling a Trailblazer weighin 4500#. The last service was done about 3K miles ago and all the filters were changed then.I have talked with several folks and they say I should be getting 8-9 mpg out of that set-up.. I am doing a number of short trips with the longest being a 450 R/T up and down I-5 in Wash and Oregon.I run around 62 mph and in 5th gear and try to keep the rpms at 1900-2000..What else can I do?
Is there a re-flash from Cat or something else?

[EngineerMike]

That certainly isn't great mileage given the weight & displacement. I'm getting 8 w/a "425" hp, 8.9 liter Cummins pulling 4500lbs behind 31,000lbs. Is that a mechanically injected rig? If so maybe the injector springs are weak. do you have a lot of residue in the tailpipe indicating over-fuel in the combustion mix?

[OneRVer]

I average 9.5 mpg. I run at 1800 rpms in sixth gear. Approx 63 mph.

[Martind4]

We've been averaging over 9 mpg with the toad (Jeep Grand Cherokee) for the last month. Wind affects us a lot and tailwinds are welcome. Generally travel between 60-62 mph w/o cruise. 3126B with 113,000 miles.

Maybe time to have the valves adjusted?

[geodays1]

2001 Dutch star , 72k miles 7.4 to 8.5 mpg based on gallons consumed and miles run. However with a Cat computer Flash it pointed out the average life consumtion over 62k miles was 7.4 average and average speeds were 62mph. I also tow an extended trailblazer! Always run with Cruise control on and mode on on the Allison
I feel its normal.

[autofish]

2001 Horizion 34BD with 3126B towing 04 jeep GC. Speed, wind, and hills make a big diferance with mpg from 6mpg to 10.6mpg but the cat compter has an average of 7.8 over 55k miles. However if I keep the speed at 55mph it will av. 9.5 -10 tank after tank.

[Garbageman]

As said before it might be time to take it to a CAT shop and have diagnosed for any problems.
I just completed a trip from the Oregon Coast, over the coast range to Portland and then up I-5 to Bremerton, WA, and averaged 8.45 mpg. I have a 36 ft Ultimate Advantage and I was pulling an enclosed trailer with my racecar in it, 7200lb. gross, travelling between 55-65 mph. I was surprised and pleased at my mpg.

Paul

[WOODYDEL]

Changing the speed you travel can make the biggest changes in your mpg. Air resistance varies with the square of the speed, and the power needed to overcome it varies with the cube. This is true whether your engine is running optimally or not. Sometimes a small increase in speed will give better mpg which doesn't make sense but anything which travels above 65 mph will decrease their mpg. Differences in MH weights will make a difference big enough to make a comparison between them difficult.

[WOODYDEL]

There is another invisible killer of mpg. Your dual tires all have to have the same pressure. A tire lower in pressure than the other is like mildly applying your brakes. Tires of the same diameter are mandatory as well. Go to Bridgestone and Michelin websites to verify this.

[OneRVer]

Also helps if you use a quality fuel system additive. The injectors will get dirty and needs to be cleaned. I am not saying to add the additive each time you fuel up but you should add some a couple of time per year.

[bigdog]

My last trip was r/t from Bremerton to Harrisburg Or for the Camp Freightliner and I got 7.2 and that was I-5 all the way towing the Trailblazer at around 62,most of it in cruise and 5th gear staying between 1900 and 2100 RPMs. The tires were ALL at 95#,we had a whole section of class on tire pressures,and I don't run any additives in the engine as I keep the fuel tank full between tanks and it's not suggested by the manufacturers.

[OneRVer]

Quote:

Originally Posted by bigdog My last trip was r/t from Bremerton to Harrisburg Or for the Camp Freightliner and I got 7.2 and that was I-5 all the way towing the Trailblazer at around 62,most of it in cruise and 5th gear staying between 1900 and 2100 RPMs. The tires were ALL at 95#,we had a whole section of class on tire pressures,and I don't run any additives in the engine as I keep the fuel tank full between tanks and it's not suggested by the manufacturers.

Yes I know, they never suggest additives. But when ever I get down to 8 mpg and I add fuel additive, my mileage will go back up to 9.5 to 10. That is the honest truth. My last trip to Mt. Hood going up the north side, Hwy 35 to Sandy OR., climbing that steep long grade pulling a jeep I got 10.5 gpm. On the freeways I run at 1750 rpm at around 62 mph.

Keeping your tanks full helps keep the moisture out but you still get contaminated fuel. That is one reason injector's will fail.

[WOODYDEL]

Have you followed the flat towing procedures in your owner's manual? Not all Trailblazers are the same.

An additive for your fuel which will not make you unhappy is Star Tron diesel additive. It's cheap.

I can usually beat my cruise control in MPG. Especially, with any hills. Though not fashionable I would try a slightly lower speed. Max out at about 58 mph and use your foot instead of cruise. That's about a 6 1/2 percent decrease in speed..

[WOODYDEL]

bigdog, I have found what you need. Actually, everybody could use this.

https://ohe.cat.com/cda/files/287140/7/LEGT5364.pdf

Makes sense to me.

Thank *** I was saying the right stuff. My trip to Alaska last year limiting my speed to 55-57 mph paid off. Short trips don't really matter. It's the long one's which really pay off.

That sound you hear is me patting myself on the back.