Fill tyres with nitrogen and gain 5% MPG ?

sassy_one

I have nitrogen in all my tyres, they put this is for nothing when I had all my tyres changed last.

I have found that it has maybe given me an extra mile to the gallon however it's such a small return I can't say for sure

Lum

A typical car tyre will be inflated to what? 28psi? Which is 2 atmospheres.

When the tyre is fitted to the rim, it's already full of air, which is 78% nitrogen, 22% other gasses. If you then inflate them with air these proportions stay the same, with a 100% nitrogen inflation you should end up with about 7.33% other gasses (78/22 + 100/0 + 100/0 divide by 3). If these other gasses are so quick to escape and deflate your tyre then they're still going to do so.

By contrast aircraft tyres are inflated to a couple of hundred PSI, at which point the quantity of other gasses is pretty much insignificant.

So "they do it for aircraft tyres" isn't a valid sales pitch for this service.

sassy_one

Lum wrote: »

A typical car tyre will be inflated to what? 28psi? Which is 2 atmospheres.

When the tyre is fitted to the rim, it's already full of air, which is 78% nitrogen, 22% other gasses. If you then inflate them with air these proportions stay the same, with a 100% nitrogen inflation you should end up with about 7.33% other gasses (78/22 + 100/0 + 100/0 divide by 3). If these other gasses are so quick to escape and deflate your tyre then they're still going to do so.

By contrast aircraft tyres are inflated to a couple of hundred PSI, at which point the quantity of other gasses is pretty much insignificant.

So "they do it for aircraft tyres" isn't a valid sales pitch for this service.

Late evening Lum


I only had it has it was free when I had the tyres fitted, I think it's a just a market scam but heyho.

Lum

Well assuming the statement that nitrogen won't seep through your tyre walls is correct then it will make a difference in how quickly they deflate. If it's free then it's worth doing. In theory your tyres would deflate at 1/3rd of the rate they would normally.

I've seen places charge up to £10 for this service though, and for that money, I'd rather just go out there with a footpump every so often and pump them back up.

sassy_one

Lum wrote: »

Well assuming the statement that nitrogen won't seep through your tyre walls is correct then it will make a difference in how quickly they deflate. If it's free then it's worth doing. In theory your tyres would deflate at 1/3rd of the rate they would normally.

I've seen places charge up to £10 for this service though, and for that money, I'd rather just go out there with a footpump every so often and pump them back up.

Agreed.

On another note, my Mondeo is doing 15 MPG instead of it's average 22-23 MPG the past week, thought it was maybe me, but have checked it 3 times now on filling up and I've defo lost 7-8 MPG somewhere

skiddlydiddly

When did you last clean/replace your air filter?Have you got a leaky fuel pipe/injector?

haveibeendone

Quote from Kwik Fit Web site

Nitrogen

Filling your tyres with nitrogen may seem odd but that’s exactly what motor sport and aviation professionals have been doing for years. Nitrogen is completely safe. And by using it in a mixture with oxygen to inflate your tyres the theory is that it’s possible to negate the issue of slow deflation, which is caused by oxygen slowly infusing through the tyre wall from the atmosphere.

The above text taken from the KF web site says using nitogen in a mixture with oxygen. Is that not what air mostly is.

I am confused.

Also how would the oxygen "infuse through the tyre wall FROM THE ATMOSPHERE".

cyclonebri1

haveibeendone wrote: »

Quote from Kwik Fit Web site

Nitrogen

Filling your tyres with nitrogen may seem odd but that’s exactly what motor sport and aviation professionals have been doing for years. Nitrogen is completely safe. And by using it in a mixture with oxygen to inflate your tyres the theory is that it’s possible to negate the issue of slow deflation, which is caused by oxygen slowly infusing through the tyre wall from the atmosphere.

The above text taken from the KF web site says using nitogen in a mixture with oxygen. Is that not what air mostly is.



I am confused.

Also how would the oxygen "infuse through the tyre wall FROM THE ATMOSPHERE".

Agreed, low pressure to high pressure migration I think not, otherwise tyres would increse in pressure:rotfl::rotfl::rotfl:, maybe they mean "difuse" or on the other hand have'nt got a clue.

The only tangible advantage of nitrogen fill is in high performance cars that are driven very hard, on track or such like. Nitrogen gives much less thermal expansion than air. Still can't see any use for it on the road.

Coveredinbees!!!!

sassy-one wrote: »

I have nitrogen in all my tyres

In that case it has to be baloney :rotfl:

fatbelly

If this slow deflation argument had any logic to it, they'd use CO2, which is a larger molecule than N2 or O2