Anyone overcoming gas prices by hypermiling?

[cute fuzzy bunny]

Bunch of bad ideas in general. Mostly stuff that saves you a few pennies now and costs you more later on.

Many vehicles are designed for a specific tire footprint and inflation rate. Changing that may result in changes to handling and braking. Overinflation wears your tires out in the middle fast while leaving tread unworn on the edges.

Pulse driving wears on a number of driveline components.

Tailgating can get you dead fast. You need to get within 10 feet of the truck in front of you to get a mileage boost. At that speed, you'll need to keep adjusting your speed to avoid crashing into the truck and keeping to within 10 feet. That on-off-on-off the gas can end up costing you mileage.

Eliminating unnecessary trips and driving under 55mph with properly inflated tires, avoiding any leadfooting and observing the traffic ahead of you and modulating speed gently to suit will offer pretty good gas mileage.

I just adopted a great strategy for picking up 7mpg. I started driving our Rav4 as my primary car instead of the Pilot.

 

[free4now]

My manufacturer recommends 33psi, but I find I get the best handling at 42psi. I used to always dread having to convince servicepeople that I knew what I was talking about and 42 was the right pressure for my tires, but recently I found a great workaround: I just made my own sticker that says 42psi and stuck that over the manufacturer sticker on the inside of the door and in the glove compartment.

Another thing I do for mileage is get regular alignments. Most people don't know that for $150-$200 you can buy a lifetime 4 wheel alignment warranty for your car. I bring the car in around every 10-15k miles, and every time they find something slightly out of spec. It's a bit of a hassle but also saves on tires because you get full warranty miles out of them.

Drafting? No friggin way.

 

[calmloki]

B) There is *some* evidence that a car can get slightly better mileage with the higher grade. It's slight enough to make it a bit tough to tell fill-up to fill-up.

C) The higher grade gas tends (I have not checked lately) to be a fixed amount higher (like 10 cents) than lower grade, rather than a % higher - this is important.


So, if you get say, 5% better mpg with high grade (say 21 vs 20), and it is a dime more, that is a wash at $2.00 gas. But, a dime added to $4.00 gas is a smaller % increase in cost, and makes higher grade fuel a good buy.

Even if those numbers are close - it's only about 2% gas price savings. But no risk, no effort.

So, anyone have good figures on premium vs regular mpg and cost delta?


-ERD50

I run a '93 BMW525it - station wagon - as a work truck for the rentals. It has an automatic and is loaded with supplies, making it pretty uninspiring to drive. It also has knock sensors, so can use regular gas, though premium is recommended. Premium continues to be $.20 more than regular, though the cost of both has gone up a buck. The price difference has shrunk a bunch as a percentage. Bought an engine performance chip from a respected maker (Mark DaSylva) and now must use premium. I now use about 20 gallons less gas/year, though that gas costs me about $91.60 more. So the chip, aside from it's purchase price, costs me about $20 extra/year figuring $3.60/gallon gas over my 11,000 mile/year average use.

My smile-age is way up though, and i consider the chip to have been one of the best things done for the car. Performance is much improved at all RPM ranges.

Also run the tires with several pounds more pressure (check your manual for suggested loaded pressures).

 

[Bestwifeever]

Re drafting behind a semi on the highway--wouldn't that hurt the semi's MPG to be pulling you along? I could see some sudden stops on the truckdriver's part to deal with that problem....

 

[Notmuchlonger]

Re drafting behind a semi on the highway--wouldn't that hurt the semi's MPG to be pulling you along? I could see some sudden stops on the truckdriver's part to deal with that problem....

No, because you are in the air the semi already cleared. (which is a super simple explanation)

Thats the problem sudden stops.

 

[Zathras]

Tailgating can get you dead fast. You need to get within 10 feet of the truck in front of you to get a mileage boost.

The tests I saw and from what I have seen there is a noticable benefit to following a semi as far as 20 car lengths. True, the most benefit is at 10 feet, but I agree with you on that, it would be crazy.

 

[Bestwifeever]

No, because you are in the air the semi already cleared. (which is a super simple explanation)

Thats the problem sudden stops.

Ahh, I see--thanks. I was misunderstanding.

 

[UncleHoney]

I find the biggest single helper is to use a light foot on the accelerator and brake.

So right you are Zathras.

DW's car has a trip computer that gives a direct readout of fuel mileage. It's amazing what just a little restraint on the accelerator yields in fuel savings. Even at highway speeds small changes can save big bucks over the life of a tank of gas. I've found I can easily beat the cruise control, especially when you encounter long grades. Letting the car slow down just a little till you top the hill really saves gas. Easing off the gas on the way down a hill instead of picking up speed by driving down the hill adds up too.

I like to avoid the packs of cars on the Interstates that require frequent speed changes too.

I always like to drive like there's a raw egg between my foot and the accelerator. Easy does it. And learn to anticipate road conditions ahead and make small changes in speed to avoid using the brakes.

 

[RunningBum]

No, because you are in the air the semi already cleared. (which is a super simple explanation)

Thats the problem sudden stops.

This was a Car Talk question this week! They agreed with you.

 

[Notmuchlonger]

This was a Car Talk question this week! They agreed with you.

Im qualified. I watch Nascar

 

[HFWR]

But you have to be going 180mph to draft off a car.

 

[Milton]

Okay, let's consider run the numbers:

• Savings achieved through better mileage: variable, but let's say an average of $200 annually multiplied by, say, three years (before an accident happens);
• Cost of destroying your vehicle in a rear-end collision: variable, but let's say an average of $15,000 (only incurred once in a lifetime);
• Cost of funeral expenses due to being killed in said rear-end collision: variable, but let's say an average of $10,000.

So, CBA suggests the potential direct financial costs ($25,000) outweigh the potential financial benefits ($600). And that's not even considering the non-financial costs, or the indirect financial costs.

No thanks!

 

[Notmuchlonger]

Need to setup those computer controlled cars for highway driving. That way traffic would be smoother. Drafting would be possible. Less traffic jams would increase mpg.

 

[cute fuzzy bunny]

Seems theres some misinformation on octane being thrown around.

Higher octane fuel has less total energy than lower octane fuel. It is not a "better" product, with a set of engine parameters it will produce less HP and lower gas mileage.

What it IS good at is lowering the tendency to detonate prematurely in an engine with higher compression ratios and/or higher heat in the combustion cylinder. That stability is gained through a loss of total energy during combustion.

Some engines will adjust the engine timing to reduce detonation if its detected, so you can use lower octane fuels. The retarded engine timing also reduces mileage and any detonation or knock (which may be undetectable to the ear) can damage pistons and valves.

Its highly advised that you use the fuel octane the manufacturer recommends. This is also a really bad place to try and save some money.

I also see the mileage increasers are recommending a reduced viscosity oil. Unless the engine manufacturer recommends it, I would not use less than a 30 weight oil especially if you operate in a climate over 80 degrees. Engine jobs are a lot more expensive than gas.

 

[Bestwifeever]

Okay, let's consider run the numbers:

• Savings achieved through better mileage: variable, but let's say an average of $200 annually multiplied by, say, three years (before an accident happens);
• Cost of destroying your vehicle in a rear-end collision: variable, but let's say an average of $15,000 (only incurred once in a lifetime);
• Cost of funeral expenses due to being killed in said rear-end collision: variable, but let's say an average of $10,000.

So, CBA suggests the potential direct financial costs ($25,000) outweigh the potential financial benefits ($600). And that's not even considering the non-financial costs, or the indirect financial costs.

No thanks!

Early inheritance and bonus life insurance for heirs and beneficiaries: priceless.

 

[ERD50]

Higher octane fuel has less total energy than lower octane fuel. It is not a "better" product,..

Agreed.

with a set of engine parameters it will produce less HP and lower gas mileage.

Sort of. If those 'engine parameters' dictate high grade only, you need to use high grade. If it is designed for low grade, then yes, high grade will give lower mpg.

What it [high grade fuel] IS good at is lowering the tendency to detonate prematurely in an engine with higher compression ratios and/or higher heat in the combustion cylinder. That stability is gained through a loss of total energy during combustion.

Some engines will adjust the engine timing to reduce detonation if its detected, so you can use lower octane fuels. The retarded engine timing also reduces mileage and any detonation or knock (which may be undetectable to the ear) can damage pistons and valves.

Exactly - and this is why some say that in a car designed to take a range of fuels (many of today's vehicles), high grade may improve mpg - because it can adjust the timing for better efficiency.

My guess is that if you drive conservatively anyhow, you will rarely hit those times when the engine needs to retard the timing to avoid knock (normally only under hard acceleration). So I also guess that high grade won't help conservative drivers get better mpg, but it may be possible.

Its highly advised that you use the fuel octane the manufacturer recommends. This is also a really bad place to try and save some money.

Yes, don't try a lower grade unless your manual says it is OK, like I said.

Seems theres some misinformation on octane being thrown around.

Where was the misinformation on octane? I missed it.

-ERD50

 

[ERD50]

My smile-age is way up though, and i consider the chip to have been one of the best things done for the car. Performance is much improved at all RPM ranges.

Do these still meet EPA regulations for emissions?


-ERD50

 

[ziggy29]

It's not worth an extra 5 MPG to significantly increase my chances of plowing into the back of an 18-wheeler. I don't care how much gas costs.

 

[ERD50]

Is the maximum PSI printed on the tires themselves an unsafe pressure? Would that PSI cause uneven wear on the tires, does anyone know?

No, the max is okay.

Leonidas, are you certain that is good information?

The way I look at it - the tire is one component; the car, it's weight, suspension, etc, are others that make up a system. I don't think it is correct to take one specification of a component, and assume it is good for the whole system.

Car suspensions are designed with the PSI that is on the sticker. Going beyond that range may not damage the tire, but it could adversely affect handling of the car, and make it less safe. I wouldn't do it unless the manufacturer said it was OK, and I personally think you should tell any passengers that they are in a car that has been modified past it's design limits. Maybe they'd rather walk.

My tires are rated for 170mph - but I doubt my brakes are! And the cylinder head bolts are probably rated to take 200 ft-lbs - but that is *not* the correct torque spec for the cylinder head. I think you are making potentially dangerous assumptions.


-ERD50

 

[free4now]

Overpressure is probably safer than underpressure. I don't have any statistical evidence, but it seems to me I've never suffered overpressure problems. Most of my tire failures in the past have happenned when I hadn't checked the tire pressure in a long time; I'm guessing the tire had too little pressure so the rim scissored it going over a bump.

A larger contact patch will also increase the amount of road debris (e.g. nails) collected by the tire. Also a large floppy contact patch has a tendency to work debris into the tires, whereas a small taut contact patch has a tendency to push debris away.

The right amount of pressure is the amount that causes even tire wear... the environmental and monetary costs of replacing tires early are not worth any gas savings that might accrue from hyperinflation. I measure my tread depth (center and sides) every time I get an oil change with a $2 gauge, so I know that my 42psi gives more even wear than the 33psi manufacturer recommended pressure.

 

[ziggy29]

The right amount of pressure is the amount that causes even tire wear... the environmental and monetary costs of replacing tires early are not worth any gas savings that might accrue from hyperinflation. I measure my tread depth (center and sides) every time I get an oil change with a $2 gauge, so I know that my 42psi gives more even wear than the 33psi manufacturer recommended pressure.

The manufacturer of the vehicle may be making recommendations based on the smoothest ride, not necessarily what's necessary for the rest of the vehicle to perform as it should.

 

[calmloki]

Do these still meet EPA regulations for emissions?


-ERD50

Some chips do, some don't. As i understand it going through the testing is very spendy, so while some aftermarket chipped cars may post better scores for emissions than stock chips they may not have undergone testing for all states. Superior power, tractability, emissions numbers, and fuel economy is achieved with better fuel maps, the chip taking readings of all the different sensors that give inputs for adjusting timing and fuel pulses more frequently, and tightening up the tolerances on timing for instance. BMW-wise I think Conforti is 50 state legal, Dinan is legal in California, DaSylva is not legal in California. I run DaSylva cause it has better dyno performance throughout the rpm range. California residents who happen to have left a DaSylva chip in their E30 have passed smog tests with super numbers. Good enough for me -

 

[maddythebeagle]

But you have to be going 180mph to draft off a car.

I personally just go to the truck stops and chain my vehicle to the semi's rear axle while the trucker isnt looking.....if you use a long enough chain, you have plenty of breaking distance....

 

[Leonidas]

Leonidas, are you certain that is good information?

Multiquote is not working for me today, so you'll have to go back to the first page of the thread to see my original post where I said overinflation was not a good idea due to handling, safety and wear issues.

I am certain that inflation up to maximum PSI is okay for tire wear, but that you have to fill them cold and be aware of temperature changes from environmental factors to avoid overinflation.

You are correct that almost everybody should run their tires at the recommended PSI (look in the owner's manual). Personally, I tune my tire pressure by adjusting it by a few PSI at a time until I find the spot where ride and handling feel right. It's usually very close to what the recommended PSI is. A couple of pounds of pressure difference can make a vehicle feel and act very differently.

However, when I was w*rking I usually kept my tires at, or very close to max PSI. It significantly improved handling, but I felt every little bump in the road. It also tended to track along with grooved pavement (not a good thing to have happen in curves at 140). But we ran V or Z rated tires and I also had lot of training and experience in how far I could push the car at different speeds and with that much inflation in the tires.

I have blown whole tires stores full of sidewalls over the years, but those all were because I got overly aggressive in a turn and my apex point was a curb that I kissed a tad too hard. The only negatives that I ever worried about were that tires with high inflation can break free from the pavement if you push them hard enough, and (I believe but can't prove) that they tended to hydroplane easier. The first wasn't too big of a problem because you had to be really aggressive in shifting weight around to make them break free - like a J-turn - and there were times when I needed to do some of things I could do when I aggressively shifted the car around and made the tires break free - like a J-turn. The hydroplaning thing scared the crap out of me though, and if it was raining I usually dropped the pressure down a couple of PSI at a time until I felt comfortable pushing the car a little.

I see your points and agree, although I think that anyone on this forum who is looking to boost gas mileage while talking about "imagining an egg on the accelerator pedal" is very unlikely to get themselves into trouble by riding on fully inflated tires. And if they are, then they probably aren't paying attention to anything I say about tire inflation - or saving gas.

 

[Texas Proud]

Some engines will adjust the engine timing to reduce detonation if its detected, so you can use lower octane fuels. The retarded engine timing also reduces mileage and any detonation or knock (which may be undetectable to the ear) can damage pistons and valves.
quote]

Yes... I have a car that 'requires' 92 octane... but it says you can get by with 87... but reading up on the results, it retards the timing and whatever else it does and the HP is lower and also the MPGs are lower...

And my thought.... if you paid a bundle for a car that NEEDS high octane then why cheap out and buy low octane fuel Decided upfront what grade gas you want and buy a car that uses it...