Pablo - where do you go for bio?

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2006 Jeep Liberty CRD, Limited
GDE Eco Tune, GDE TCM Tune, Bauer 203* Tstat, Amsoil EaA 201 Filter, Clean MAP, Samco CAC Hoses, Magnaflow Muffler #12226.
New Mopar Fuel Filter, K&N Filterminder, Fumoto Oil Drain Valve
225/75R16 Hankook Dynapros

I saw this topic come back to life a few days ago and figured I'd add my latest personal record.

Houghton, MI to Alpena, MI - 375mi - 9.643 gallons ($24.00) = 38.88mpg

Actually the odometer only said 346mi, which would be 35.88mpg (still awesome) but I believe the actual distance was about 375mi, especially considering the construction detour. This was under IDEAL driving conditions, meaning sunny weather, light traffic and a light tailwind.

CRD is stock except for SEGR and EHM, tires are at 50psi. Cruise set at 60-61mph (indicated) and I try to grab 5th gear as much as possible. This is, as I said, a new record by quite a bit. Usually I'm in the low 20s, lucky to get 30 on most trips. Easily in mid-teens in winter. If it matters, it's an '06 with about 34k on it now.

On a side note, I got my first CEL a few days ago on the way up there, it came on just as I shut off the cruise coming off the Seney Stretch. Went to three places trying to get the code read over the next couple hours, then it just went off by itself and I haven't seen it since. Everything seems fine, I'm hoping it was just a false reading?

Nice! What psi are your tires rated for?

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2006 Jeep Liberty CRD, Limited
GDE Eco Tune, GDE TCM Tune, Bauer 203* Tstat, Amsoil EaA 201 Filter, Clean MAP, Samco CAC Hoses, Magnaflow Muffler #12226.
New Mopar Fuel Filter, K&N Filterminder, Fumoto Oil Drain Valve
225/75R16 Hankook Dynapros

...may want to bleed your fuel head. I get a CEL from time to time because of this...have a new head that should arrive soon and need to install the lift pump. Outside of the lag on take off, it runs fine otherwise.

Why is this thread still called "Gas" mileage?

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Manure green 2005 CRD sport4x4, GDE Hot tune, Cat Gut, OE skids, Draw tight hitch, Duramax lift pump, 160K on multiple varieties of fuel, XM radio, Escort live with Redline, fog light mod, GPS, Icom IC7000 all band radio call sign KC9QPF, Grabber AT2s on Soft 8s, FIA grill blanket.

Azbiodiesel

With the GDE tune my wife went from a 19mpg (heavy commuting traffic ) average to 26 and she has a lead foot. Haven't done any freeway yet but stock she was getting about 26 freeway.

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Chris
Current:
2007 Steel Blue Metallic Grand Cherokee CRD Limited
GDE Eco Tune and DPF delete
CB Engineering DPF delete pipe
EHM

Past (sold to Mountainman):
2005 Patriot Blue Liberty CRD Limited

My tires are rated for 44 psi, so going five over (ok, they're at 49 not 50) is not too crazy.

I'll check the fuel head, it could've been that. I've never experienced the stuttering or lag other people report, so I haven't worried about it too much. Thanks for the suggestion.

I don't know why it's still called "Gas Mileage". Is there a way to change it without just starting a new thread?

I think 26mpg freeway, in the winter anyway, sounds about right to me. I don't get on freeways much though.

some of my wvo buddies that hypermile jetta tdis use nitrogen in e-rated tires,rides like a brinks truck,but 65-70 MPG ain't nothing to complain about.Lots of little things will help alot. I get 24 MPG in a 8,600 lb ford excursion by running tires at max,and going 62mph,and thats on WVO (which has 8%-10%less cetane then ULSD,also less BTUs per pound.MPG is 1/2 car and 1/2 driver..........H

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2005 greaser KJ,jeeper greaser

Using nitrogen in road tires is a waste of money. Racers use it so they can have a known expansion rate of the air vs heat regardless of ambient conditions. Air in different places and at different times has different amounts of water vapor and other bits that can cause the air to expand at different rates as the tires heat up - this can cause a change in expected traction. On the race track where you're on the edge of performance this is important. On the road it is pointless.

My guess is they're "hyper" inflating the tires. Don't need nitrogen for that. Personally I'll trade a few mpgs for saving my kidneys and having some traction available in case I need to stop suddenly or turn quickly.

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Chris
Current:
2007 Steel Blue Metallic Grand Cherokee CRD Limited
GDE Eco Tune and DPF delete
CB Engineering DPF delete pipe
EHM

Past (sold to Mountainman):
2005 Patriot Blue Liberty CRD Limited

Oh yes...the nitrogen in the tires bit...one of my biggest pet peeves. There's this lore that oxygen diffuses through the rubber at a faster rate than the nitrogen is therefore the is the reason "air is inferior." More probably leaks through the seal of the valve stem or the seal around the rim than any possible rate of diffusion. The lack of water vapor is the only plus and that could be accomplished with dry air. My next pet peeve...Shell's commercials for their "nitrogen enriched gasoline." I think they're playing off of the tire thing. What a load of crap. In regards to tires, manufacturers work hard to arrive at the recommended tire pressure for specific reasons...safety being the first one and economy being the next one.

Tell me why every tire on every commercial jet uses nitrogen and also the small jets. When I worked at Southwest the mechanic would check the tires of every jet that overnited with a little bubble of nitrogen and very rarely would he have to add any nitrogen to any tires, even after a whole day of takes offs and landings the pressure would stay very constant. Just an observation about nitrogen in tires.

I found this on a google search....:

"More important, nitrogen doesn't support combustion, which is one reason aircraft and the space shuttle use nitrogen in their tires. The wisdom of this precaution was brought home by the crash of Mexicana Airlines flight 940 on March 31, 1986. Shortly after the Boeing 727 took off from Mexico City en route to Puerto Vallarta, an overheated landing-gear brake caused a tire improperly filled with air instead of nitrogen to overheat as well and explode, rupturing fuel and hydraulic lines. The ensuing fire and crash killed 167 passengers and crew. However, unless your driving habits are of the X-treme variety, the chances of your tires catching fire anytime soon are slim"

Can anyone guess what this is a picture of?

Temp. extremes, at 30000ft it can be -40C to-70C, your CRD tires stays nice and warm on the ground.

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06 LIMITED 100000miles, MAGNAFLOW, HOMEBUILT CCV FILTER, POLAR PAD, 02 AIRBOX, CUMMINS LIFT PUMP, SEGR, PILLAR GAUGE POD, CAT FILTER MONITOR, SPYDER TRAX, ALWAYS A LITTLE TWO STROKE OIL OR BIO, WATER/METH INJECTION

the nitrogen is so that I can get in my Excursion,@-15F,drive non-stop to fort Myers FLA without worrying about temp flux and over inflation.All the blow-out you see going south are usaully from tires that are not monitored during extreme weather changes in a short amount of time(-15F to +80F ambient in 26 hours).The best maintence is a well designed set-up,with longevity AND performance in mind,I run 12 ply E rated Nokian Vativa tires @ 78PSI,80PSI being max.I hope to get the same set-up for the CRD and will let you know how it improves MPG..............H

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2005 greaser KJ,jeeper greaser

Get them in a 215/85 and it will improve quite a bit. I know it has on mine with the BF Goodrich commercial E-rated in that size.

It's not to say that there isn't benefit to having nitrogen in automobile tires, but a lot of the stuff that is advertised/explained is more based on marketing than actual science.

It doesn't matter where you're using normal air or nitrogen, the air pressure is still going to increase on the order of 20% with that temperature range. The good thing is that you don't have the water vapor which probably increases the pressure at a greater rate. So if you're starting at 78 psi when it's -15 F outside and going south, you're going over the 80 psi max pressure limit anyway.

Use P2 = P1(T2/T1) where P is pressure (units don't matter since it's a ratio) and T is the temperature (units need to be in Kelvin).

That's what I didn't understand about the nitrogen claims - don't all gases (heterogeneous or homogeneous) obey the idea gas law under normal passenger tire usage conditions?

- Chris

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Used to own:
2006 CRD Sport
Suncoast TC, Transgo shift kit, Inmotion, ORM, EHM, Magnaflow SS exhaust, Fumoto valve, EVIC added, Hensley TruControl brake controller, Pirelli Scorpion ATR LR-D in spring/summer/fall, FIA winter front and Blizzaks in winter

nitrogen does not expand at the same rate as air,it is much slower to expand,alot of truckers use it for this very reason.And the 80 psi would be cold temp with a percentage over cold max allowed for expansion,based on AIR,so there is a plenty of flex for nitrogen use...............Ask any northern trucker that goes south of memphis in the winter months what he has in his drive tires Air or Nitrogen? hands down nitrogen.And it adds a little more cargo before you tip the scales..

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2005 greaser KJ,jeeper greaser

Well...none of these are ideal gases...but this approximation is the best we have without doing a lot of extraneous math that I don't remember how to do.

That's the thing, nitrogen is really no better in terms of inflation than other gases. The pressure increase with temperature is going to be nearly the same for nitrogen and air since its 80% nitrogen. Not having water (or water vapor) present is the only plus since it can lead to rust in steel wheels. Water vapor will increase in pressure at a faster rate with respect to temperature than the nitrogen or air which is were it also becomes a problem.

There's nothing wrong with using nitrogen in automobile tires. It is beneficial. But the marketing and stated benefits are over the top. Monitoring your inflation pressures will largely accomplish the same benefits in terms of fuel economy.