True Dennis - and made worse by some brands of pneumatic tools used in auto shops that are supposed to have a trace of oil in their air for lubrication.  I'd think that most body shops would have good air and oil separators though, as oil or water in the air makes a hash of spray painting - even cheap 1/8 hp hobby systems come with decent air and oil separators.

But my point remains - nitrogen for filling tires is an excuse to sell you an expensive and unnecessary 'add on'. 

I will admit that I check my tire pressures on dry days, not in the pouring rain, to minimise the amount of moisture getting into them - I can't access the college's pneumatics air supply for my tires!

James
Festo Pneumatics Instructor
Ottawa ON

> Date: Tue, 20 Oct 2015 23:11:02 -0400
> From: d23haynes57@HOTMAIL.COM
> Subject: Re: Nytrogen and tires
> To: vanagon@GERRY.VANAGON.COM
> 
> Very few automotive or even body shops not have equipment to remove moisture
> from their compressed air systems. Heck most don't even adequately deal with
> the oil carry over from the pumps. There are various methods used to remove
> moisture from compressed air with the most being refrigerated dryers or
> desiccant systems. The effectiveness of air dryers system is measured using
> the dew point.
> 
> Dennis
> Compressors up to 350 HP and clean, oil free air systems drying to dew
> points of -40f.
> 
> 
> -----Original Message-----
> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of
> James
> Sent: Tuesday, October 20, 2015 10:07 PM
> To: vanagon@GERRY.VANAGON.COM
> Subject: Re: Nytrogen and tires
> 
> Dry air is expensive to generate?   Funny, it's 'generated' in pneumatic
> equipment all over North America on a daily basis.
> 
> The pneumatic doors at your local food plant or airport aren't powered by
> nitrogen gas - dry air is much cheaper!  Another 'justification' for
> charging you $10 for nitrogen that costs 5 cents - and replaces 2 cents
> worth of air.
> 
> James (who teaches pneumatics as part of his course load) Ottawa, ON
> 
> > Date: Tue, 20 Oct 2015 11:16:53 -0600
> > From: jondvo@GMAIL.COM
> > Subject: Re: Nytrogen and tires
> > To: vanagon@GERRY.VANAGON.COM
> >
> > The reason Nitrogen is used is because it eliminates water vapor
> > issues with freezing. Nitrogen is free of water vapor and "dry" air is
> > as expensive to generate.
> >
> > On 10/20/2015 9:55 AM, Angus Gordon wrote:
> > >> PV = nRT ( T in Kelvin)
> > >> It's all you need to know Angus. For tires, balloons, business
> > >> meetings :)
> > >>
> > > I knew I'd been missing something. It's all about hot air, says
> Alistair...
> > >
> > > Angus
> > >
> > >
> > >>
> > >>> On Oct 19, 2015, at 3:53 PM, Angus Gordon <birdworks@GMAIL.COM> wrote:
> > >>>
> > >>> Thanks David, I've been using a rule of thumb of 1% per 5F for a long
> time but I don't know where it came from. Michelin perhaps. Normally I only
> use it to overinflate when headed to a cold destination. Kept me out of the
> weeds so far...
> > >>>
> > >>> Angus
> > >>>
> > >>>
> > >>>> On Oct 19, 2015, at 3:46 PM, David Beierl <dbeierl@attglobal.net>
> wrote:
> > >>>>
> > >>>> At 11:19 PM 10/17/2015, Angus Gordon wrote:
> > >>>>> I have experience with nitrogen filled tires on aircraft and can
> tell you that it certainly doesn't negate pressure changes with temperature.
> That's still something we deal with. I don't see any real value in using
> nitrogen in car tires.
> > >>>> I believe pressure change as a percentage per degree will be
> essentially the same no matter what gas or combination of gases is used to
> fill a tire.  It amounts to roughly one psi per ten degrees Fahrenheit for
> tires at ordinary pressures and temperatures.
> > >>>>
> > >>>> Yrs,
> > >>>> d