The tires have tread wear indicators on them. Now, I have not been riding at 50psi the entire life of the tire more like ~2000-1500 miles.

As far as holes, I know where the bad spots in the road and can dodge them, however, I am usually not driving fast enough to do any damage if I do hit the bad areas of the road that I encounter.

 

This is true- visit ANY cave. I have explored several in the CA Gold Rush area, many abandoned mines in So Cal desert areas like Joshua Tree Monument, and over 100 coal, uranium, and shale oil mines in UT, CO, and MT. The only temperature difference would be if you pumped gas right after a tanker dumped a load that had been cruising down a very hot freeway for hours. Even then, the warm gas just delivered would chill back down quickly in the cool underground tank.

 

You guys have probably already looked into this a bit, how much better MPG do you get riding on such pressures as 35 vs 40 vs 45 vs 50 ?

For me I tend to check my pressure regularly mainly to ensure safety and catch problems early on; but also to maintain good mileage (I usually get about 40mpg on the highway despite all my modifications geared towards performance.... although I haven't had a chance to track how the new engine management system impacts that, but that is another story).

I know for you guys who participate in the cleanMPG site the mileage is almost a status symbol. But for folks on here that might be interested in getting good mileage and still maintain the full ability of the tires, I wonder what the compromise pressure would be?

Just a side note; something else came to my attention today about the high PSI. I would imagine that your suspension is going to take a beating. If you get more than a year or two out of your shocks before they start sagging I would be impressed. Maybe something like this; https://www.fitfreak.net/forums/fit-...tml#post312380
for the rears to extend the life?

 

I know when I had my psi at 40(because I was to chicken to rock the 50psi) I was having a hard time achieving 42mpg. When I inflated to 50 psi 45mpg was a piece of cake and my max mpg was 47.9mpg I believe. This was in my thread labeled Stock air filter vs. K&N air filter. I drove the speed limit, used cruise control and the A/C(only on the 2nd half the daily commute). With that said, I have not performed a test to isolate strictly psi but it was a constant and the only difference was the air filters and the obviously daily variables such as weather and traffic.

For now, I am stickin with 50psi. Though I am interested in whether or not it will prematurely wear out the tires, hell I don't even know how many miles these tires should last.

That brings me to another question:

Any one know of some good tires that would yield better mpg? I would imagine a lighter tire but I would like something that would last so that would obviously NOT be a sticky tire, since I am not a track star.

 

I was running 32psi when I achieved 42mpg on the way to and 44mpg from on my vacation destination last year. So many factors though... I was already running variety of mods, I have a feeling the tire size was a big factor because with the slightly larger diameter I was keeping the RPM under the Vtec engagement at highway speeds.

If I were to take my best stab at it, you are looking for two things; First, the treadwear rating would have to high and second, I think you would probably be looking for a tire that has a consistent contact with the road along the center. Anything with interrupted tread lines is going to grab a bit of friction as it impacts.

Another thing you could look at is maybe width. You could run a 185 tire instead of a 195 to further reduce your friction.

Actually now that I am thinking about it, the tires I have would probably be a good candidate. There is no interrupted tread line and the wear rating I believe it better than other tires.

Continental - ContiSportContact 2


I really wish you guys would run 40psi though just in case something ever happens, the car really starts to loose it's abilities at anything more than that

 

I know it's already been said many times here and in other threads but the driving habits in my experience have a profoundly bigger impact on mpg than anything else including tire pressure. I have bumped mine up a bit to 44. Even after warming then they are still within the craplop's max rating. I didn't notice any difference in mileage from that. The difference seems to me to come 97% from cutting speed, avoiding quick acceleration, buffering and coasting vs braking.

 

For those who are recommending to use the OEM's recommendation of tire pressure, do you know for what load that recommendation was made?

I seem to remember max tire pressure was for a full car.....

 

Pressure would be for the max axle loads, should be in your owners manual.

I already mentioned this, but generally the max PSI is determined by the tire and has nothing to do with the car. The tire will have it printed on the side somewhere for safety reasons.

 

DV - I think the load is determined in part by the tire's pressure, not the other way around. But I did a little reading on tirereack and others (Tire Tech - Tire Specs Explained) and it appears that the max load the mfr recommends may not directly correlate to the max psi they recommend, even though that would make sense. Given the tire markings are nearly always higher than what mfr says is "recommended" for "most" driving, honda is probably giving you an artifically lower inflation value to err on the side of traction and safety (given the ramifications, I think they care a lot more about safety than you getting the greatest possible mileage). Also, they have no idea what tires people might decide to pop on.

 

I see what you are saying, but still the max pressure is going to be dependent on the tire. The tire will be rated for a certain load (which I doubt the Fit will exceed even with over weight axles loads), if you exceed that load then you compromise the tire and it basically is at risk of a premature blow out.

As long as you don't exceed the load spec for the tire you can inflate up to the max PSI written on the side safely. I believe the lowest rating you can have is 50psi, people inflating tires over that sidewall marking are at serious risk of having it blow up in their face!

Now, that doesn't mean running at the max PSI is safe, your traction becomes compromised because without the proper amount of weight on the tires it will have a tendency to bulge out along the bottom (which is what the hypermilers are taking advantage of, less surface area means less friction and increased mileage)

You may be correct about the recommended Honda PSI being low. They may have adjusted that PSI to suit an unloaded car to maximize the traction as more of a safety factor. However officially speaking, that is the pressure that should accommodate the max axle loads. I would say that if you constantly run with more weight in the vehicle it wouldn't hurt to use 3 or 4 more lbs of pressure to ensure you are getting the right mix of traction and economy.

 

I have no chips in this pissing match, but will offer this fact. The 2008 Sport Dunlap tires say 51psi Max on the tire.

If you fill them to 50 at room temp, I assure you they will be greater the 51 after driving in warm to hot weather. No idea how warm they get in cold weather.

I live in South Fla and the roads get very hot here. Also the shell aggreget makes them get even hotter from extra friction. When I 1st started looking at this for my car in Feb, I experimented some. I posted the results on this site for all to read. I used a IR thermal gun and measured mine after driving for 30 min. Trust me, they get hot. The front a lot more than the rears for obvious reasons. Anyway, what I found is 45psi is the most I want at room temp to leave room for the expected and verified pressure increase at operating temp.

I doubt anyone on here knows how much over eng these Dunlap's are so I'm treating 51psi as it says max. Sugest you do as well

Now carry on.

 

For the people claiming significantly increased mpg with higher tire pressures: have you decreased the tire pressure and observed a decrease in mpg?

I ask because I've observed a significant increase in mpg for my fit over the first 8000 miles I've driven. Part of that has been my driving habits, but part of it could be "breaking in" the car. So perhaps the increase in MPG observed with increased tire pressure could be more from the Fit being "broken in" than the increased tire pressure. Or not.

 

I wouldn't say there is a pissing match going on, just discussion.

I believe that the max tire rating is going to be cold PSI, there is a previous post to an article on Tirerack which talks about this.

With that said, 51 psi is way to freaking much!!!

The theory behind it is pretty solid, however with a little attention to keeping the recommended PSI it will also yield better MPG. I think the problem is with a tire or two that is under inflated will start to eat into it much more noticably.

 

I recently experimented with 40 psi in the tires and didn't like the way the car handled. The steering was too light (similar to the way it feels when the tank is almost empty) and the car required more frequent steering corrections to stay on course.

My main gripe was the loss of traction in bumpy corners. Oklahoma roads are terrible - 40 psi really caused the car to lose its composure when the roads turned rough.

I promptly went back to 32 psi. I don't feel that any improvement in rolling resistance is worth the tradeoff in safety. My most recent tank came in at 40.4 mpg - that's good enough for me.

 

If you get dirt into your engine, wouldn't it affect the oil? Bad oil = bad mpg!!! I'd rather keep it clean for engine safty reason.

Depends on which set of tires. We are driving front wheel vehicles so it's ok to overinflate the back wheels. All those do is drag... As mentioned before, read the sidewall of your tires to see what's the max PSI. There should be a warning that says "Inflating over xx PSI may result in bearing seal damage" or something like that.

What competition? I see only 4 or 5 different gas station brands around here. Most of them are Mobile, Shells, and Arcos. If they were really competing against each other, one company will ramp up production like crazy to gain the extra margin of business. The gas stations are competing, not oil refineries where additives are inserted. The mobile 2 blocks away from me probably gets the same price of gas as the mobile 5 blocks in the other direction. But the gas station sells at different price for profit margin/competition.

 

Yeah on the Premium thing, I use to have a 94 Prelude that said Premium only, but ran just fine with no low octane ping on Regular. I'm sure there was a slight drop in performance but I tried premium for a month and didn't notice any difference.

What surprises me is that link to the Top 8 most fuel efficient cars. 8 was the Yaris which was stated to get 32mpg...which is worse than a fit.

 

It won't affect the oil. A dirty air filter does not let dirt in, it keeps air out.

A dirty air filter becomes clogged with crud and can't pass as much air through. With a dirty air filter the engine can't breathe as well and it won't be able to make as much power. The ECU will compensate for the lower amount of air by adjusting the fuel accordingly, hence no loss of fuel economy -- just a loss of performance.

 

That makes alot of sense. But I sometimes see the smudge on the wrong side of the filter. And if you keep them for too long, they tend to wear out. The good thing about the fit's air intlet is that it prevents rocks from flying into the airbox unlike my previous car. I guess I can conclude a clogged filter is ok, but a damaged filter is bad!

 

Tell you what : clog half or more of your air filter and see if you don't lose mpg; the faster you go the worst it is.

Some manufacturers tell you to use premium because their ignition system can't handle low test gas and results in detonation. And often premium has higher energy components than low test in order to attain the needed octane rating. The higher the energy rating in btu per lb the better gas mileagre you will get, all other things equal. Is it worth more than 8 cents per gallon at 3/gal? I doubt it nowdays. I agree that you should use the lowest octane gas the manufacturer recommends.

 

[
That brings me to another question:

Any one know of some good tires that would yield better mpg? I would imagine a lighter tire but I would like something that would last so that would obviously NOT be a sticky tire, since I am not a track star.[/quote]

Cavalier, sorry, cobalts, recently improved their mpg ratings by going to lower rolling resistance tires like the Prius uses. Unless you get a 'touring' Prius, which has regular tires and loses 2 mpg in the rating.
If you drive in the mountains on crooked roads the 'ergular' Prius is a handful. Some RV's will out corner you. You don't get low rolling resist for nothing. These guys running 50 psi should see the same reduction in cornering plus wearing the center of their tread. When the center gets down to 2/32" the outer grooves will be 10./32.
Anyway, if youre looking for low rolling resistance tires check the ones on Cobalts now.