Improved Fuel Mileage!

[slickbrave]

About a month ago, I had my tires rotated and the tire dealer suggested I let them put nitrogen in my tires. He said Nascar has been doing it for some time now and the advantages are: nitrogen doesn't change pressure based upon the weather like air does, it gives a smoother ride, it would prolong the tread wear on the tires, and it would give better fuel mileage. I was skeptical, but they would only charge me $10 since I bought the tires there, so they removed they removed all the air and replaced it with nitrogen, replaced the stem cap with a green one so I wouldn't forget, and away I drove. I can't tell much difference in the ride, but I check my mileage religiously, and I am getting 1 1/2 to 4 MPG better. I have made no other changes, so I think this might not be snake oil.

Anyone else tried this?

 

[bmw046series]

How did he fill them with Nitro?

 

[slickbrave]

He had a separate tank of nitrogen. It looked similar to an air tank except it was green. If you google "nitrogen tires" you'll see a lot of information. I'm a believer.

 

[m5runner]

I have done that before in my ride. It makes a big difference in the summertime and is definately worth the money if you live in hot climates. Nitrogen doesn't "improve" gas mileage. The entire concept behind it is if you use nitrogen, your tire pressure will remain the same despite the outside air temperatute. Planes use nitrogen so that when they climb 30,000+ feet, the tires on the landing gear stay the same pressure for landing.

 

[Wadula]

plus, notrogen filled tires tend to not loose pressure over time. that is a pretty neat security and convenience feature in my books.

 

[sm32589g]

does the tire pressure decrease? like if you maybe lets say accidentally hit the stem and release a pound of pressure what would you do? im wondering because maybe i should put nitro in my tires

 

[m5runner]

the pressure won't decrease unless you let it out. ofcourse it will go down after time, but i can assure you that it will be a very long time before it does, if ever. I always nitro up when I get new tires. Putting nitro in tires that are older and more proned to getting flats may be a waste of time and money. Not sure how well your funds are in the GW era, but mine are short, hence recharging once a year.

 

[Big Daddy]

I crewed on a NASCAR Southwest Tour car for many years and yes we used nitrogen in the tires, however we evacuated the tires first so they were filled with 100% nitrogen. Tire dealers are not evacuating your tires first therefore you are not getting 100% nitrogen in them. Consider that Nitrogen’s coefficient of expansion is .8, as compared to air’s 1.0. So there’s only a 20% difference in the reaction to temperature changes. Let’s say (to make the math easier) that your tire pressure goes up by 10 PSI after this test, running regular air. (test: Fill a cold tire with air to 32 PSI, run it about 50 miles on an 80 degree day, then chek it again.) With Nitrogen, it’ll go up by more than 8 PSI. As I noted above, the coefficient of expansion of Nitrogen is .8 as compared to air’s 1.0, and your tires won’t be filled with pure Nitrogen. At best, you’ll get a 2 PSI difference. In reality, it’ll be less than that.

The theroy is that you get better gas mileage and tire wear because the pressures remain more stable with nitrogen, this is extremely with NASCAR due to stagger. It does not make that much difference with you street car and therefore if it costs you for the nitrogen it is overkill. I understand that Costco uses it at no extra charge.

 

[slickbrave]

What's involved in evacuating a tire besides removing the valve core to let the air out? If you put Nitrogen in new tires from the beginning, this would definitely be a non-issue. I have no scientific proof, but if the 2 extra MPG I'm getting are due to the nitrogen, it shouldn't take too long to recover a $10 investment.

 

[Big Daddy]

Evacuating the tire is done with a compressor where the air is sucked out of the tire until it collapses in on it's self. The tire is than filled with nitrogen. A properly inflated tire, regardless of the gas inside of it, maintains the correct footprint on the road, which minimizes squirm and rapid tire wear and drivers get better fuel mileage because a properly inflated tire has less rolling resistance than an underinflated one, it has nothing to do with the nitrogen. However considering that 80% or so of the drivers on the road today never check their tire pressure there is an advantage to them using nitrogen, but they are not the types that will!

Here is a popular mechanics article on the issue: Click Here Their bottom line, "Bottom line: I'd fill new tires with nitrogen if the tire shop will do it for free or at least at a discount. Most will. But just cruising in and topping off from a nitrogen hose for 20 bucks? Save your money."

 

[slickbrave]

I would agree that $20 for topping off with Nitrogen would be a waste. In my case, I had a bent wheel that had to be replaced. They mounted my tire on the new wheel and filled it with Nitrogen, then removed the valve cores from the other 3 tires and let the air escape, obviously not to the point of the tire collapsing on itself, so I know not all of the air was removed. Then the 3 tires were "filled" with nitrogen. This cost me $2.50 per tire for a total of $10. Since the tires only had around 4K miles on them, I figured what the heck.

 

[sm32589g]

cool thanks what would be good new tires for a 1999 323is m-package? i kind of want eagle f1s but if you guys know any ones that are better please let me know. oh and i want sporty tires i dont drive the car in the rain or winter for that matter.

 

[sm32589g]

?????

 

[slickbrave]

I like Michelins.

 

[DSK]

We are in the tyre trade here in the UK.

Firstly the Nitrogen thing is slowly picking up here in the UK, few large establisments use them, mainly on high performance vehicles only. We are getting one in the next month.

As for filling tyres with 100% Nitrogen, we would only do it provided the wheel rims are in good condition and are not leaking. Leaking rims can usually be cured with sanding down any rough rusty spots and then treaded with a bead sealer. All tyres are fitted with new valves (stems?) and then will be filled with Nitrogen. This will ensure that only Nitrogen is in the tyre.

As for tyres, I like Goodyear F1, they always perform awesomely regardless of the conditions but they some how seem to last a respectable amount of time too.

But I have just put Pirelli P-Zero Assimetrico on my 328i and I love them just as much, they get the power down better, have phenominal grip in the dry and are decent enough in the wet considering that the outer 1/2 of the tyre is like a semi-slick! But they wear faster than Goodyear F1's and are a bit noisier.

Continental Sport Contact is another top brand option, very good in the dry and wet and they have decent levels of communication. The Sport Contact '2' is actually a very quiet tyre but isn't as good in the wet due to the continuous bands on the tread.

Michelin are always priced around 20% more than its competitors. They are supposed to last a bit longer than all the others and is generally quieter but is that extra 20% really worth it considering that tyres from Pirelli, Goodyear and Continental are in the same league with 'performance' levels to match and exceed Michelin?

(BTW- I have Michelin Pilot Sport on my Volvo C70 T5 at the present moment on test)

To be honest, you can't go wrong with the above manufacturers especially with their high performance range of road tyres, but everyone has a different driving style and prefers a different feel, so I guess try a few and see what suits you.

For what its worth, I run my cars as follows.

BMW 328i Coupe
Summer = Pirelli P-Zero Assimetrico
Winter = Goodyear F1

Volvo C70 T5
Summer = Pirelli P-Zero Assimetrico
Winter = Continental Sport Contact 1