How do I maximize Highway MPG?

[cheezy]

45-50 PSI in tires, use ethanol free fuel, have the oil level in your car at the halfway point between the 'stick marks of High & Low.

 

If your commute is nice and level, NOT hilly, use the Eco-cruise function.

 

Enjoy.

 

Our Dealer I just picked the car up from had the Oil level over the "Full" mark and the front tires were both under 40 P.S.I. Simple fixes. 

 

Enjoy!!

 

 

 

If you want the easiest way to remove oil from the Dealer's possible overfill, grab yourself a Pella oil vacuum pump from any mariner supply shop online; straw hose goes down the dipstick hole, and vacs oil out. Great for complete oil changes as well. 

Edited July 16, 2015 by cheezy

[ptjones]

Then again you could remove ICE cover and drain out some oil from drain plug which doesn't require spending any money. Easier to do when the oil is cold. :)

 

Paul

[Taz]

One other thing to consider as well besides mileage, is resistance to hydroplaning. There is a direct relationship between psi and speed at which a tire hydroplanes. From my flying days I was taught to take the square root of the PSI, multiply it time 9 and the will equal knots at which the tire can begin to hydroplane.

 

Since most of you don’t deal with knots for speed, a quicker, but not perfect version, is to take the square root of the PSI and multiply it times 10 to get MPH.

 

30psi =  ~55mph

35psi =  ~59mph

 

40psi = ~63 mph

45psi = ~67 mph

 

50psi = ~71 mph

55psi = ~74 mph

 

As you can see, even just being mildly underinflated can put you at risk of easily encountering hydroplaning in wet weather. At the high end, you are crazy to drive much over 65 mph in the rain with stock tire pressures.

[fbov]

One other thing to consider as well besides mileage, is resistance to hydroplaning. There is a direct relationship between psi and speed at which a tire hydroplanes. From my flying days ....

... At the high end, you are crazy to drive much over 65 mph in the rain with stock tire pressures.

While generally true, especially over a wide pressure range, you may want to revisit the assumptions before extending it to automobile tires.

 

Speed

Planes land fast and slow down. Cars start at rest and speed up. The latter has the option of sensing a reduction in grip before it's lost. The former has to make an estimate in the air, with no good alternatives to landing. Expect a very conservative rule-of-thumb as a result.

 

Tires

Plane tires are designed for drag racing - 0-to-100 MPH in 0.5 seconds! As such, they are crowned, so only the center makes contact initially. That makes tire pressure a direct driver of contact patch size, and hydroplaning is very sensitive to contact patch size.

 

Tread

Drag racing tires don't have much tread. Neither do the aviation tires I see in a quick search. That's a direct result of landing stresses, which no car tire will every see in normal use. If you've ever driven the famous Italian racing tire, the "Baldini," you know how valuable tread is in the rain.

 

And it's tread that makes your last statement pure nonsense. Tread depth and road water load/drainage are far stronger effects that tire pressure in the 40-50psi range. C-Maxers who choose to retain OEM pressures are not in additional danger of hydroplaning as a result of that choice.

 

So, your post has good stuff in it, but I don't see how it applies.

 

HAve fun,

Frank

[ptjones]

Assuming tire has significant tread (not Baldini :) ) the higher the pressure/smaller contact area would be less affected to Hydroplaning than  less pressure would be.  When I first had MADMAX  using 38psi  I ran through a  deep puddle during a rain storm and almost had the steering wheel ripped from my hands, WOW that was scary.  Now at 50psi it's not so bad. :shift:

 

Paul

[Taz]

And it's tread that makes your last statement pure nonsense. Tread depth and road water load/drainage are far stronger effects that tire pressure in the 40-50psi range. C-Maxers who choose to retain OEM pressures are not in additional danger of hydroplaning as a result of that choice.

 

HAve fun,

Frank

 

Many roads have inadequate drainage. Maybe at one time they did but I have been on many highways, all over the US, where the trucks have created "ruts" where there is a significant amount of standing water when it rains. I have been in some states where it appears the people who designed the roads put absolutely no thought into drainage. A few extra PSI can make a difference. 

 

As for tread depth, it is in a state of continually decreasing. I prefer to err on the safe side. I subscribe to the adage "There are old pilots and bold pilots, and no old, bold pilots." I have thousands of hours in aircraft from sub-sonic to Mach 2+. I never wait for my tires to get down to the treadwear indicators. Considering I am often driving in relatively extreme climates it isn't worth the risk to me or my family. Like most things, tires are a compromise. Unfortunately you don't always know what the compromises were until it is too late.

 

Even with almost full tread depth (3k miles on the stock tires and pressures) I encountered significant hydroplaning at about 60 mph outside of ABQ on a recent trip. There was standing water on I-40 and thankfully I had slowed down from about 80 when I first noticed the wet roads. The truck in front of me didn't. He must have rolled 3 or 4 times after losing control while spewing parts all over the highway. I don't know if he and his passengers survived or not. If I had maintained my previous speed I am not sure how it would have turned out for my wife and I. As it was, I lost total control for about a second or so. So while the maxims I learned regarding fly may be conservative, they likely saved our lives.

 

At a minimum it will at least have people here thinking about this topic whereas it was never mentioned before. At least with an aircraft landing at high speeds on runways, I was not dependent on the tires generally for directional control until I lost authority with the control surfaces. I don't have the option of adding a little rudder to compensate for a skid.

[ptjones]

I agree with Taz having flown my own airplane for 13yrs. and also know about the "ruts" on I-40. :)

 

Paul

[Redshift]

One other thing to consider as well besides mileage, is resistance to hydroplaning. There is a direct relationship between psi and speed at which a tire hydroplanes. From my flying days I was taught to take the square root of the PSI, multiply it time 9 and the will equal knots at which the tire can begin to hydroplane.

 

Since most of you don’t deal with knots for speed, a quicker, but not perfect version, is to take the square root of the PSI and multiply it times 10 to get MPH.

 

30psi =  ~55mph

35psi =  ~59mph

 

40psi = ~63 mph

45psi = ~67 mph

 

50psi = ~71 mph

55psi = ~74 mph

 

As you can see, even just being mildly underinflated can put you at risk of easily encountering hydroplaning in wet weather. At the high end, you are crazy to drive much over 65 mph in the rain with stock tire pressures.

Sorry, that's a silly statement. I took a 5000+ trip this summer. The speed limits in Wyoming and South Dakota were just raised to 80mph. I drove my C-Max at 85 mph. It was raining (torrential) and I never had any kind of a traction problem. My tires are at 40lbs, factory setting.

[Taz]

There is more to hydroplanning than just tire pressure. If the road is grooved like some highways that lessens the risk. The amount of tread on the tire, the siping, etc.

 

Whether you want to believe it or not, there is a relationship between tire pressure and hydroplaning. You don't have to believe me though, go here.

 

http://www.nhtsa.gov/cars/rules/rulings/TPMS_FMVSS_No138/part5.6.html

 

and here 

 

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=3

[fbov]

There is more to hydroplanning than just tire pressure. If the road is grooved like some highways that lessens the risk. The amount of tread on the tire, the siping, etc.

 

Whether you want to believe it or not, there is a relationship between tire pressure and hydroplaning. You don't have to believe me though, go here.

 

http://www.nhtsa.gov/cars/rules/rulings/TPMS_FMVSS_No138/part5.6.html

 

and here 

 

https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=3

Just to be clear here, both of these links deals with the dangers of under-inflation. We're discussing the opposite.

 

Is there any reason not to increase tire pressure from door placard values to tire sidewall values?

 

Have fun,

Frank

[ptjones]

Just to be clear FORD's placard says 38psi front and back, Michelin says 51psi MAX cold.  I have been running 50psi for 80k mi. , first set lasted 64K and I'm getting great gas mileage.  I don't see a down side to this. :)

 

Paul

[Taz]

Under inflation is relative. Quite often car manufacturers choose a PSI level that is a compromise, like almost all other aspects of the car. Most often on a "normal" car, they bias it toward the lower end of the spectrum for better ride quality but not so low as to maybe have a significant hit on mpg.

 

Higher PSI does reduce the risk of hydroplaning. I experienced it very severely already in the car at stock tire pressures. I am currently at 48 psi  and the car has been driving great. Best mileage so far and tire wear is very good. Ride quality didn't suffer as much as i thought it might.

 

The car is a bit more nimble too which is a nice plus when trying to conserve momentum through turns. Only on a fairly rare occasion am I reminded that the pressure is higher than stock.

[SPL Tech]

.

 

Higher PSI does reduce the risk of hydroplaning. I

Maybe, but it also increases the risk of flying off the road in every other possible senario. You need tire contact pach area for grip in snow, wet conditions, dirt, mud, and even dry pavement. If you increase the PSI, you lose grip in all conditions except driving through standing water in a turn.

Edited September 14, 2015 by SPL Tech

[fbov]

I have to disagree in the most strenuous terms. This is bunk. Back it up with some real data or delete it.

Frank

[ptjones]

I agree with Frank, Please supply some facts to backup your claims or Delete your Post.  There is too much misinformation out there and we don't want to get Members confused. ;)

 

Paul

[ptjones]

I have been noticing that my HWY FE has gone up this year especially this last month. My overall average this this year seems to be 2 mpg better than last year and it looks like I'm averaging around 54 mpg HWY.  The only difference I know of is using 0-20W Mobil 1 and K&N oil filter which I can't see them making much of a difference. My tires are down to 5/32" which might make a slight improvement. :headscratch:  :detective: ;)   I haven't changed my FE driving habits. :shift: 

 

Paul 

[BIG ROCCO]

I have been noticing that my HWY FE has gone up this year especially this last month. My overall average this this year seems to be 2 mpg better than last year and it looks like I'm averaging around 54 mpg HWY.  The only difference I know of is using 0-20W Mobil 1 and K&N oil filter which I can't see them making much of a difference. My tires are down to 5/32" which might make a slight improvement. :headscratch:  :detective: ;)   I haven't changed my FE driving habits. :shift:

 

Paul 

The tread depth might have more of an effect than you think...???

 

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=177

 

At the bottom it says:

 

Conclusion

While many of these individual differences may seem insignificant, it is easy to understand that when they are added together, the new tires may appear to reduce vehicle fuel economy. It also means that a Toyota Prius appearing to get 50.0 mpg just before replacing its worn-out tires with new tires of the same brand, type and size, might be reduced to registering just 47.25 mpg afterwards, even if all of the driving conditions were identical.

[ptjones]

The tread depth might have more of an effect than you think...???

 

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=177

 

At the bottom it says:

 

Conclusion

While many of these individual differences may seem insignificant, it is easy to understand that when they are added together, the new tires may appear to reduce vehicle fuel economy. It also means that a Toyota Prius appearing to get 50.0 mpg just before replacing its worn-out tires with new tires of the same brand, type and size, might be reduced to registering just 47.25 mpg afterwards, even if all of the driving conditions were identical.

Interesting. :)  so much for the 47/47/47 mpg, I've blown that out of the water. :yahoo:

 

Paul

[fbov]

The tread depth might have more of an effect than you think

+1

 

Look at LRR tire specs, and many have less tread depth than similar tires from the same maker. Our OEM's are 9.5/32, not 10/32 or more. Save a little here, a little there....

 

HAve fun,

Frankl

[ptjones]

I have been thinking about why my FE has gone up 2mpg on the HWY and the only thing that is different is I added the NOS Octane Booster racing formula and it claims to clean injectors. A year and a half ago I used Chevron Techtron injector cleaner so I guess it's been 50K mi. approx. since I've cleaned the injectors.  Strangely enough my City FE hasn't improved noticeably. ;)  

 

PS: Just checked and Winter Blend gas get less MPG's than Summer. :drop:

 

Paul

Edited November 13, 2015 by ptjones