Tips on Stretching Your Non-Hybrid Car's MPG

Discussion in 'Start Your Journey Here' started by SkeeterVT, Jun 11, 2007.

  1. diamondlarry

    diamondlarry Super MPG Man/god :D

    Hmm, maybe the fact that my tires are a bit north;) of 60 psi explains the numbers I'm getting in a still green Prius.
  2. DoubleJ

    DoubleJ Member

    So, you're saying that my tires, with a MAX of 35# that I have inflated to 45# cold are going to be ok? I was really wondering about this as we come up on summer.
  3. SkeeterVT

    SkeeterVT Member

    I've had the misfortune of suffering a blowout on the New Jersey Turnpike during an extremely hot summer day in 1999. I was driving from my home in Burlington, Vermont to my brother's home in the Maryland suburbs of Washington. D.C. when the passenger-side front tire blew out. The air temperature was a stifling 98 degrees and the road surface temperature had to have been well over 120 degrees. When cold, my tires were inflated to 40 PSI, with a maximum pressure limit of 44 PSI.

    It turned out that the heat sent the pressure in the three surviving tires soaring to well over 55 PSI, with the driver's-side front tire as high as 58 PSI!! A subsequent examination of the blown tire found no evidence of a puncture -- No nails, no tacks, no broken glass.

    I should mention that these were Bridgestone tires, with over 30K miles on them. You may recall the rash of Bridgestone SUV tire failures during a particularly brutal heat wave in the South in the summer of 2001. Even today, between Memorial Day and Labor Day, I still often pass by the remnants of tires that suffered heat-related failure.

    It certainly appears to me that blowouts are more common in the summer than at any other time of the year. But I'll concede the very real possibility that MY blown tire was worn down to the point that it could no longer maintain its structural integrity.

    Nonetheless, based on my experience, I will always be leery of inflating my tires less than 5 PSI below maximum in the winter and less than 10 PSI below maximum during the summer (In fact, the owner's manual recommends 30 PSI for my car).
    Last edited: Jun 13, 2007
  4. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Skeeter:

    ___You can be leery but please try not spread disinformation here. We have the inside line on a lot of this and do know about what we speak of.

    ___Good Luck

  5. Mr. Kite

    Mr. Kite Well-Known Member

    Re: How To Read A Sidewall

    Just to clarify, it is well documented that the problem with the Ford Explorer and blowouts was with underinflation. Ford recommended running the Firestone (max 35psi) tires at 26 psi.
  6. psyshack

    psyshack He who posts articles

    Mr. Kite is correct. Also most that blew were for the most part worn out.

    I had a set of those self changing law suite tires on my 2k Ranger. I got 57k miles out of them before the stell belts in them crawled in the tire carcus.

  7. JimboK

    JimboK One owner, low mileage

    Thanks, Skeeter, for taking the time to describe your experience.

    I'm not discounting it, but yours is an anecdotal report that runs contrary to the body of evidence and the extensive experience of others. Heck, if I had experienced it, I might take the same approach. But as I look at it from the big picture, I'll stick with my current practice.

    I liken it to the guy who quickly escaped from his wrecked burning car because he wasn't wearing his seat belt. The evidence clearly says his risk of injury is greater without restraints, but because he's convinced not wearing them saved his life, he will never wear them. Again, I might do the same if I were him.
  8. Walter

    Walter Well-Known Member

    Re Tire Pressure: Other factors to consider in tire failure are previous hidden damage to the tire, manufacturing defects and the load in the car (i.e., are the tires overloaded).

    A question I have is if I am driving with the car loaded to its maximum, what tire pressure should I use? Underinflated I know is bad for a loaded car. But, does load capacity decrease when the tire is inflated past its sidewall max?

    If a tire is punctured and repaired can I still safely exceed sidewall max psi in it? When this happened with my old Civic I went back to ~30lb in all 4 tires. Other than punctures the only tire failure I've had was hitting a curb, which caused a leak. If that had been at 50 lb I suspect it would have been OK. My sons' Chevy Caprice (aka the BEAST) had a number of tire failures; probably bad rims causing slow leaks, in turn causing underinflation.

    SkeeterVT, I suspect that really hot temps are bad for tires beyond the pressure increase with temp.

  9. psyshack

    psyshack He who posts articles

    On our Accord the wife got a flat. It is pluged and I put the air psi right back up to max sidewall of 44 psi. Plug is fine.

    I think xcel has had some flats of late on his Accord. Im sure they are pluged or inside patched. One of the two. I bet his tire psi is at its normal setting.

    Tires now days are a total diff. beast than in the past. Stell belted tires have done wonders for us. :)

  10. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Jeff:

    ___Same tire and it is leaking again from what Cheryl told me last night. If I did not have $50.00 tied up in the 2 nail puncture repairs, I think I would be better off going somewhere else :( Still pressed it right back up to 62 not a mile from the Tire place.

    ___Good Luck

  11. pumaman

    pumaman Well-Known Member

    It is quite possible that there was an object that you didn't see which caused the blowout and simply didn't remain with the tire.

    I do think that a tire with lower pressure, when it hits a sharp object is more likely to retain the object in the tire which would cause a slow leak, where a highly inflated tire meeting with the same object could conceivably cause a more catastrophic type failure.

    Still, it's not the tire failing simply because of the pressure and heat, but rather it reacting differently to the trauma due to the higher pressure.

    I'm curious what the Senior Members think of this idea...:confused:

  12. JimboK

    JimboK One owner, low mileage

    And there's another possibility no one's mentioned (unless I overlooked it): a defective tire. I could see that contributing to Skeeter's high-pressure, high-speed failure.
  13. pumaman

    pumaman Well-Known Member

    Naturally just after being involved with this thread, I came out of the local supermarket yesterday and noticed that the right rear tire on my Legacy was very low. This is the first tire problem noticed since I've increased the air pressure. On the Legacy they're rated for 51 psi and I was running about 48-49 psi in them.
    Anyway the tire had some air left in it, so I nursed it the 4 miles back home. Later I took the tire off and couldn't find anything sticking out of the tread or obvious holes. So I pumped it back up but couldn't hear any air escaping. So out came the plastic tub and hose, and after immersing the tire and spinning it around for a few minutes I finally found a thin trail of bubbles coming out of a little hole the size of a #4 finishing nail.
    Whatever had caused it had not stayed with the car.
    So I got out the plug kit and fixed it up, I've done this several times in the past on various tires. The hole was so small I had to drill and then ream out the hole to a point that I could get the plug in. Filled it back up to 48 psi, checked it in the morning, and it hadn't dropped at all. Just drove it about 20 miles and no problems.

    So, older tire, high pressure, road hazard, no failure, just a slow leak easily repaired.
  14. Walter

    Walter Well-Known Member

    Later pumaman said:
  15. pumaman

    pumaman Well-Known Member

    Ya know, I kept waiting to get raked over the coals for that, but expected that would take place here, in writing. I had no idea they'd actually hunt me down and make their point in such a dramatic and personal way. Very effective though. ;)
    Last edited: Jun 19, 2007
  16. psyshack

    psyshack He who posts articles

    I got up Sunday morning to find a flat right front tire. First flay Ive had in a very long time. Found two screws in it. Took it to Wal-Mart. ( only thng open here on a Sunday ) Got it fixed with inner patches. Put the psi back at 54 and moved on.

  17. hobbit

    hobbit He who posts articles

    What's your preferred plug kit? I'm thinking I should keep one
    around... and how reliable are plugs done from the outside over
    the long haul? Usually tire places will also do an inside patch,
    but if I'm somewhere where it's inconvenient to bust the bead...
  18. ILAveo

    ILAveo Well-Known Member

    I learned to plug tires in my misspent youth when I was a car rental assistant manager (you get a life's worth of auto problems in about two months in that job). I've never had one fall out, though occasionally(for me about 1 time in 20) you can't keep a plug from having a small leak and have to get the leak fixed from the inside.
  19. pumaman

    pumaman Well-Known Member

    I've just used whatever is available at the local Auto Parts Store or Walmart. The one I'm currently using is called "Monkey Grip". They all seem to be similar. I've plugged 5 or 6 tires. I only had one that still leaked, because the hole was a little larger than normal. I just jammed a second plug in next to the first one and then it sealed up and didn't give me anymore problems.
  20. scottjustice

    scottjustice Member

    My concern has always been with the conflict that can often exist between the tire manufacturers recommendation and the automobile manufacturers recommendation. It's not at all uncommon to see the manual that comes with the car indicate one thing and the tire side-wall indicate something else. Although the difference is generally not huge, it has always perplexed me. I usually side with the tire manufacturer.

    Oddly enough, I have never, in my nearly 30 years of driving, experienced a "blow-out". Crap...I just jinxed myself! I have had a couple of flats. They were so subtle that I wasn't even certain I had a flat until I got out and looked. The point is that I had historically taken very poor care of my tires. So I'm guessing they are built to sustain even unreasonable conditions.

    One thing to note about the use of cruise control. The Eisenhower Interstate Highway system was designed with a few specifications from lessons they learned from both the older highway system and the Autobahn in Germany. Most notably was the careful use of grading. With only a few exceptions, all of the Ike highways were designed to have no more than a 6% grade. Most cruise controls today handle these grades with ease and you probably won't be able to improve much upon you're FE by doing it yourself. Mostly that depends upon how much effort you are willing to put into it. While you will find areas of non-Ike highways where using cruise control is feasible, you should also note that the steeper inclines you encounter can really kill your FE with cruise control on.

    My co-workers constantly rib me because I park at the extreme end of the parking lot where no one else parks so I can pull up next to a group of trees that provides shade for a couple of hours prior to my leaving for home. It keeps the car much cooler.

    I've found watching my rpms is much more useful than watching my mphs. For instance, at somewhere between 30 and 35mph my vehicle runs at about 1700 rpms but if I accelerate to 40 my over-drive kicks in and my rpms drop to below 1400. It doesn't matter if you're doing 15mph or 50mph. If you're running more rpms at 15, you're using more fuel.

    It should be noted that this is with pressure evenly distributed throughout the tire. Catching your tire on something causes a brief localized trauma and can compromise the integrity of the tire compound. This comment is not a slap at either of the posters but merely to point out the fundamental flaw in the method they used to rate the inflation level of the tire. Assuming they actually did it this way.

    The New Jersey Turnpike....'nough said.:D

    Defective tires? Why would a company make defective tires? That's just silliness!:p

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