The Binary Circumstance

Not too long ago, my 1987 Ford Ranger blew its head gasket.

I had another car, 1987 Chevrolet Cavalier which has been very reliable transportation for ten years, but it wasn’t any good for carrying anything.  It was originally my father’s car which I got after he died.  I had an emotional attachment to it because it always reminded me of my dad when I drove it.

I decided not to spend the money (more than $2,000) to fix the Ford Ranger because the truck was 18 years old and I’d only spent $1,000 on it to begin with.  I had really enjoyed its utility and its character.

Here’s the old Ford Ranger.

I didn’t like having two vehicles, both of them old, so I decided that I would get another small truck and get rid of the Cavalier.

A local dealer was having a huge sale of "reprocessed" cars and trucks and I found one there that I liked at a good price (after much haggling) and they even took the Cavalier in trade.  It’s a 2002 Mazda, with 70,000 miles but it looks like new, and drives really well.  It’s got electronic switchable 4-wheel drive, V6, automatic, and just about every other option you can think of.

Here’s the new Mazda truck.

Ironically, when I took it over to the Mazda dealer to get a second key made, I found out that these Mazda trucks are really just Ford Rangers inside a Mazda skin.  Ford owns a controlling interest in Mazda.

Sadly, it doesn’t get mileage as good as either my old Ranger or Cavalier, both which had four-cylinder engines.  Both of my old cars got 20mpg, with the Cavalier doing even better than that on the highway.

The salesman told me the Mazda would get about 25 miles to the gallon which was an outrageous lie.  I found out later that it’s only rated for 15-19.  The four cylinder, manual Mazdas probably get around 25.

With gas being so expensive, I started monitoring the mileage in the new truck on the first tank of gas.  The first tank only got 14.5mpg, the second 15.4mpg, and the third 14.4mpg.

Then I remembered that when I bought the original Ford Ranger, I was also disappointed in the gas mileage.  I subsequently found out the tires were underinflated and when I pumped them up to the proper pressure the truck suddenly felt like it had wings.  None of the tires had looked flat, but some were very low on pressure.

So I checked the Mazda’s tires which are larger than any tires I’ve owned before.  I saw they were rated for 80psi.  I’ve never had tires that were rated for anything over 35psi.  Should the tires really be pumped up to 80psi?

I checked the pressure and at it was between 30-35psi on all four tires.

After researching it on the Internet, I decided that the tires definitely needed much more air and I’m surprised that the dealer hadn’t properly inflated them.  The truck had been detailed and all the fluids had been changed so I don’t know why they didn’t put more air in the tires.

The sticker on the door which says the tires should be in the low 30’s specifically refers to "P" type tires which are "passenger" tires.  The new truck has "LT" type tires which stands for "light truck."  Light truck tires require much more air.

The amount of air also depends on how much load the truck is carrying.  At maximum load they are rated for minimum 80psi, so I figured since I don’t often have a full load, they should have less than that.  I found several web sites seemed to confirm that.  (The sidewalls of passenger tires give the maximum amount of pressure.)

So I’ve pumped the front tires up to 70psi and the back to about 60psi.  They didn’t blow up.

As with the Ranger, the truck suddenly felt much lighter and I noticed that it turned easier.

Underinflation is the number one cause of tire failure.  Bridgestone/Firestone blamed low tire pressure for the failure of its tires on Ford Explorers.

Low tire pressure is bad for the environment because all those tires that fail end up on the dump and fuel efficiency is compromised.  This page is a good summary of the problems with low tire pressure and the benefits of proper tire pressure.

The higher tire pressure in my truck has definitely improved the gas mileage.  The average for three tanks on the underinflated tires was 14.8mpg for combined city and highway. 

After adding more air, the average for two tanks is 16.3mpg combined city and highway.  That’s an extra 1.5 mpg!  That’s 10% better mileage just from adding more air.

I think most people hardly ever check their tire pressure.  Think how much gas and money would be saved if everybody in the U.S. habitually checked their tire pressure.

Today, it cost me $35 to buy 3/4 of a tank of gas.  I can console myself a little in the knowledge that with underinflated tires, I would have paid $38.50 to go the same number of miles.

With gas prices being what they are, saving 10% on each tank of gas will mount up quickly.

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