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Old 05-11-2018, 10:33 AM   #1
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Busting Myths

Every spring I see a lot of people asking many questions about fuel ratings, nitrogen air filled tires, vortex generators, etc...

I wanted to start this thread to educate people (It's what I do for a living) and provide solid, reliable, and applicable scientific evidence to help people navigate some of the sales pitches we get. If you have more information to add, please feel free, but be prepared to back up ANY claims with reputable sources.

Here we go:

#1 - "I want to 'treat' my car/truck/RV to some special fuel and buy premium gas"

This is a VERY common myth. Premium fuel has higher octane and costs more money. This in turn causes people to think it's 'better.' In the U.S. Octane ranges from 85 octane - 97 octane with a few degrees in between. The PRIMARY function of octane is to prevent pre-ignition. That means that a higher octane fuel will ignite at a higher temperature and compression. What does this mean for you? Your Toyota Corrolla does not need high octane fuel. It has a regular engine that does just fine with lower octane. A high performance vehicle however, has a higher compression ratio and requires higher octane to prevent the fuel igniting before the spark plug ignites. If you put low octane fuel in this kind of vehicle, you'll burn holes in the tops of pistons.... this is bad. If you hear pinging while going over a pass while pulling a TT or in an RV, fill up with higher octane and it SHOULD get better.

Another thing to note. There is no such thing as 'mid-grade' fuel. When you see the typical three grades of fuel at the pump, the middle one is just a mixture of premium and regular gasoline. HOWEVER, it's mixed at a 3:1 ratio of regularremium. Which means that it's the WORST value for money at the pump. You're better off either buying regular or premium.

If in doubt about which to buy, consult your owner's manual.
More reading material Selecting Gas


#2 - "I want the highest cetane for my diesel"

This is VERY similar to octane for gasoline, and performs nearly the same function. However, modern diesels require a higher cetane content. Also, if you live in the great frozen north, you'll need high cetane content to prevent your fuel from freezing in the winter.

Cetane Ratings



#3 - "They want money to put nitrogen in my tires.. that means it MUST be better!"

Nope. Nitrogen provide next to zero advantages over regular old air. Common statements are:
---- "It's a dry gas! It won't let things corrode inside your tire!"
While it is technically a gas that does not dissolve water vapor readily, wheel corrosion on the interior has not been an issue for 40 years.

---- "It keeps your pressure more steady when temperature changes!
This is just completely false. ALL gases expand and contract at the same rate over the same temperature changes. (Guy Lussac's Law)

---- "The molecules are bigger so it will leak less!
While technically correct... the difference between sizes is so small that effect is negligible.

The fact is this. Air that you breathe is the same stuff that gets pumped into your tires is 78% nitrogen. Unless your tire has been mounted in a special room that is 100% nitrogen, it's impossible to have your tires inflated with 100% nitrogen. The tire itself has a volume of air in it when it's mounted and the amounted of compressed nitrogen that's added is only a percentage of the volume that's already there. Suffice it to say, it's a scam.



Please feel free to post more common myths, but make sure to have sources and data to back up your claims!
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Old 05-11-2018, 10:46 AM   #2
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#4 - I want to install Vortex Generators to improve fuel mileage!

This one is FULL of anecdotal evidence, but ZERO data to back up the claims that salesmen are saying. AirTabs are a prime example. These small devices were originally developed to create steady airflow and reduce drag over airfoils like wings, rotors, and turbines, and in this fashion they are absolutely beneficial.
However, for large vehicles like semis, RVs, Trailer, etc... the effects are negligible. You are taking a device that was developed for airfoils that have a very minimal cross section over their trailing edge and applying them on something that is essentially a giant brick with a massive cross section. The effect will NOT be the same. These vortices are so small that you cannot counteract the giant drag coefficient on the back side of your rig. This is why you see those GIANT cones or aerodynamic panel skirts on the backs of semi trailers. These DO reduce drag.

In short, things like AirTabs DO generate teeny tiny vortices, and do decrease drag. But you'd only start to notice after a million miles and you may save a few bucks... But they're pretty much useless, and they have zero data to back up their claims apart from anecdotal stories.

If anybody has some hard data to prove me wrong, I'm happy to change this.
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Old 05-11-2018, 10:47 AM   #3
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#5) "The extra cost extended warranty is totally worth it."

You would be far better off taking the thousands of dollars that the extended warranty costs and put it in the bank for future repairs. Chances are, IF they are needed, it will cost less than what you paid for the warranty. And if you don't need repairs in that time, you are money ahead. Factor in deductibles, financing (because they are usually rolled into the purchase price and thus financed), and what is and isn't covered, they usually (but not always) not worth the cost.

#6) "well then... That free 'Hitch to Bumper'" lifetime warranty my dealer is touting has got to be a fantastic deal. I mean, it's FREE right?"

Not so fast... Nobody makes money by giving stuff away for free. The catch on those 'free' warranties is that you are required to bring your camper in once (or sometimes twice) a year for 'inspection'. The will give you a laundry list of things they look at. Most of them are stuff you can do yourself in an afternoon. Of course, the inspection isn't free at all. And if they make a recommendation that you have to have some service done, like rotating the air in the tires or port and polish on the hitch ball, you are compelled to pay to have that done, or the warranty will be void. If you want to see what the real value of that free warranty is, just ask the dealer how much money will they take off the purchase price if you decline it. My guess is $0, and that pretty much illustrates how much they are worth.

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Old 05-11-2018, 11:28 AM   #4
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#8 It is always best to run the MAX PSI the tire will handle.
use a load inflation chart unless you are near the max capacity of the tire.
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Old 05-11-2018, 07:16 PM   #5
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When the outside temp reaches 32 degrees, everything will instantly freeze.
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Old 05-11-2018, 07:34 PM   #6
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-A Flux Capacitor will be a great investment. LOL
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Old 05-11-2018, 08:49 PM   #7
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Quote:
Originally Posted by BandJCarm View Post
-A Flux Capacitor will be a great investment. LOL
I thought it was. I have one in the back of my pickup, the trouble is I have never gotten it up to 88MPH.
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Old 05-11-2018, 09:02 PM   #8
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The second you hit 65MPH those China Bomb's will all explode simultaneously.
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Old 05-11-2018, 11:24 PM   #9
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The following myths are in no particular order:

Ford makes the best truck.
Chevy makes the best truck.
Dodge makes the best truck.
Toyota makes the best truck.
Nissan makes the best truck.

Fact: They all have their respective problems!
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Old 05-12-2018, 12:06 AM   #10
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Quote:
Originally Posted by Cowracer View Post
#5) "The extra cost extended warranty is totally worth it."

You would be far better off taking the thousands of dollars that the extended warranty costs and put it in the bank for future repairs. Tim
In theory, that's probably the right way to do things. Same thing as folks who say never finance, save up and pay cash. If I had to do that, I'd never have an RV. Doesn't hurt me a bit to finance something. But my point is this: it's real easy to say take those thousand of dollars and put it in the bank. Some people, especially after just closing a deal on an RV, don't have thousands of dollars to put in the bank for future repairs. That's where an extended warranty could be advantageous. If it's going to up your monthly payments by twenty to thirty dollars, that's affordable. I've bought extended warranties before, and had to use them. Glad I had them. It's just what fits your lifestyle and your budget whether to get one or not. IMHO, they do have their place.
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Old 05-12-2018, 12:12 PM   #11
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When you buy an extended warranty, you are betting that something bad will break. The seller is betting that nothing will break.

It’s bad juju to bet against yourself.
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Old 05-12-2018, 01:58 PM   #12
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There is no perfect RV.

You buy what you can afford. Then you fix-it-up to your taste. Then you almost have a perfect RV with one more thing to fix.

I had a TT and two class Cs before I purchased my Class A. It is perfect for me because my DW enjoys the ride & it fits in my driveway, but I am still fixing things.

I replace the toilet with a Dometic 320 toilet. A must for my DW.

There is always one more thing to fix or improve.
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Old 05-12-2018, 02:00 PM   #13
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I also have life insurance I really don't want to use, either!!!
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Old 05-23-2018, 06:33 PM   #14
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Quote:
Originally Posted by joshuajim View Post
When you buy an extended warranty, you are betting that something bad will break. The seller is betting that nothing will break.

It’s bad juju to bet against yourself.
When I said "No thanks" the salesman said "So you are a gambler, huh?" I told him actually the opposite.

Then I pointed out that just moments ago the floor salesman was telling me that this unit was absolutely amazing and they couldn't possibly drop the price one dollar more. Now you are telling me that unless I buy maintenance insurance, the thing will fall completely apart before I get it home.
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