Gas Mileage (Improved with Nitrogen filled tires??)

[Pioneer]

This is my first attempt at a thread, i briefly looked to see if this issue has been addressed, and i know we don't buy these vehicles for better gas mileage, but here we go...

Just bought a 97 tlc 80 in Las Vegas last month...
the guy i bought it from claimed he got 21 mpg on highway...
drove it back to Albuquerque NM and got 20 mpg during the last leg of the trip from Flagstaff to NM...
filled up on cheveron 88 octane...
wouldn't have believed it if i didn't calculate it myself...
Was with a fellow mudder of High Desert Cruisers here in ABQ who helped me buy the tlc...
he couldn't believe it either...
was runnin michelin light truck tires 270/70/16's on factory wheels...
semi bald tires... on snowy road conditions on I-40...
no other mods...
fram air filter and oil filter, castrol oil...
drivin about 75-80 mph...
Biggest mod... Nitrogen fully filled tires...
just as all military aircraft landing gear tires are filled with nitrogen...
ofcourse we know that we can't adjust our air pressure as easy as natural air...
can we carry around nitrogen tanks to make adjustments...
is it worth it...
guess it depends on how much we off road...
maybe it's worth carryin an extra set of tires, just like snow studded tires...
does it run the tires down quicker...
i guess we're talking about density...
expansion/contraction... pros/cons...
thoughts, questions, concerns, advice...
v/r

Pioneer
ps... i welcome all salutes...

 

[Romer]

Welcome,

I hadn't heard of this before. So where did he get the nitrogen to fill the tires?

This looks to be a good technical discussion.

 

[jditom]

Sounds like you have a nice tig there!


Welcome

Tire air pressure will change mpg. But nitrogen alone should not. The advantage is your tire hardly ever looses any pressure so they are always right were you left them. They can save mpg by keeping tires at proper pressure. You can do the same with regular air but you need to check and add air more frequently. For most of us mud compulsive types this is not a problem

 

[cruiserdan]

Nitrogen? Better fuel mileage because of?

 

[Cruiserdrew]

This has come up before. There is no good argument for using nitrogen in a street driven truck. There may be specialized applications where Nitrogen may have a marginal advantage-like a race car or a military jet.

What is air? It's 81% Nitrogen already. Most of the rest is oxygen with some argon and CO2 thrown in. There is no difference in thermal expansion-at our temps and pressures air and nitrogen both behave like an ideal gas.

Keep your tires inflated, but don't waste money on nitrogen fills.

 

[tech_dog]

OK...

<hijack>

I've always wondered about you guys that use CO2 tanks. With mountain bikes, using a CO2 charge causes your tires to slowly lose pressure as the CO2 works its way through the rubber.

Is slow pressure loss an issue when you fill your big offroad tires with CO2?

</hijack>

 

[Cruiserdrew]

OK...

<hijack>



Is slow pressure loss an issue when you fill your big offroad tires with CO2?

</hijack>

Yes, and it isn't that slow.

 

[jamisobe]

Looks like the thinking is that heat causes rolling resistance and Nitrogen dissipates heat quicker (hence the military using it in airplane tires). Nitrogen also seeps slower than air.

http://suvs.about.com/od/tiresandwheels/a/nitrogentires.htm


They guy in the article says not to go out of your way for Nitrogen. Costco fills them with Nitrogen for free.

 

[Beowulf]

was runnin michelin light truck tires 270/70/16's on factory wheels...

I think you mean 275/70R16 tyres. I don't think they make 270's.

Your 20mpg calculation is likely from some type of error. We had one guy that swore he was getting a certain MPG and after about 2 weeks of pounding on him for details on how he was calculating the mileage we found out he was estimating the gallons consumed based on the dash gauge. Another guy claimed abnormally high MPG figures and he was calculating wrong ... can't recall the details but he was waaaay out there on the math.

A stock 80 will get somewhere around 16 highway and 12 city. If you nurse it at 55 MPH, unloaded, no A/C, windows up, tyres inflated to 40+ psi, tailwind, and downhill, you might get 17-18 using reliable consumption calculations.

You've changed tyre sizes now so you have to take the 6% error into account on any MPG calculations you make. Also, your odometer could be off so check it with a GPS.

Congrats on the new Cruiser!

-B-

 

[chibo]

There has to be something wrong with your calculations or something, I'd kill for that kind of gas mileage

 

[Pioneer]

Beowulf,
you're probably right...
some sort of fluke...
but we filled up on gas in flagstaff and rolled down hill probably with a snowy tailwind, no cruise control, and filled up again near Gallup NM boarder some 150 miles away...

But seeing how the previous owner swears by 21 mpg's when he was driving it cross country, and i calculated at 20 mpg's...
we ran the calculation twice and couldn't believe it...
i really still don't...

which is why, I'm still wondering if it's logical to go with Nitro filled tires...

oh, and yes, they were 275/70's...

pioneer

 

[joinerman]

Try this site to get your mpg

www.mileagecalculator.co.uk


Joinerman

 

[Romer]

When I bought my truck and drove it from Dallas to Denver in stock condition I averaged 18. Then I reached altitude and ethanol gas and it went down to 16. Next came lots of toys, bigger and then bigger again tires and well . .

we didn't buy these for their gas mileage.

 

[firetruck41]

Try this site to get your mpg

www.mileagecalculator.co.uk


Joinerman

That works if you buy gas (petrol) in Liters.

 

[GXO]

If you add unobtainium 230 to your gas you can get 32 mpg

Agreed, we didn't buy these for fuel efficiency...and nitrogen does nothing but ensure proper pressures as temp and time change, nothing more.

 

[SR.GRINGO]

So I don't live in the U.S. any longer but I started wondering why everybody had green tire caps on thier cars. Costco fills with nitrogen--apparently in hot/cold weather the pressure doesn't change as much.

 

[RavenTai]

OK...

<hijack>

I've always wondered about you guys that use CO2 tanks. With mountain bikes, using a CO2 charge causes your tires to slowly lose pressure as the CO2 works its way through the rubber.

Is slow pressure loss an issue when you fill your big offroad tires with CO2?

</hijack>

Yes, and it isn't that slow.

That does not make any sense, C02 is a larger molecule than both nitrogen and oxygen the major components of air,

Nitrogen is used in aircraft tires not because of any thing great about nitrogen it is more about what is not in it, water being the biggest thing any water in a tire will be ice after a few hours at altitude, also water will cause corrosion of the rim, also pure nitrogen contains no oxygen and therefore cannot be a fire hazard,

but the biggest reason is that it is hard to fill a tire to 205 PSI using 115 PSI shop air and we have left over nitrogen cylinders with low pressure from filling 3k psi accumulators door bottles and alike.

 

[Bambusiero]

If tire heat causes any change in rolling resistance, then air and
nitrogen will be practically identical in that respect.
N2 molecular weight = 14
O2 molecular weight = 16 -> not much different, and it's only about 20% of the volume anyway.

I think the reason for jets using N2 is that at very high tire temperatures the O2 could support either oxidation/degradation or
outright fire. Max performance braking down a few thousand feet of
runway makes for hot brakes. For some odd reason those folks take a dim view of fire and blowouts,
can't imagine why.

If you plan on reducing your tires to the size of buggy wheels, fillling 'em up to 200psi and doing max performance stops from
200 mph, then I would ignore these naysayers and go for the N2.

 

[DesertCruiser]

FWIW, I don't really buy into the whole nitrogen thing. My other car (1984 Mercedes 300D) has tires purchased from Costco, and thus nitrogen in them. I consistently lose more air than I ever have before in any vehicle with any tire. This is about the least technical response you'll ever see here, but it's just an observation.

 

[Grench]

For all intents and purposes the air we breathe is mostly Nitrogen.
Check http://en.wikipedia.org/wiki/Air

N2 78%
O2 21%
Ar (Argon) 1%
The remaining 0.037680% is irrelevant to this issue.

The whole N2 tire fill thing was a brilliant marketing maneuver by tire stores across the nation. Here they could put $0.25 worth of gas in 4 tires and charge $16.

Why do they fill military aircraft tires with it? Because it is bone dry and there will be no condensate pooled up in the tire. Unless you're going to be driving at 36,000+ feet, this isn't an issue.

Run your compressor to pressure, fill your tires with good 'ol air. What you're putting into your tires is drier than the air you breathe simply as an effect of the compression cycle. Be sure to let that water out of your compressor at the end of the day through the drain cock.

Nitrogen inflation is pointless and a waste of the energy used to purify the Nitrogen in the first place. Make (nearly) pure N2 for yourself if you like. You can do it by burning something, catching the gases coming off, then compressing it until all of the oxygenated compounds fall out as precipitate. Tada... a stream of dirty water and a stream of nearly pure Nitrogen. If you want a laboratory grade, you'll have to do a few more steps to pull out the Argon, etc...

It isn't rocket science. Its marketing. If it were rocket science we would be filling up with Argon.