Good bye Good Mileage??

[bsams]

I didn't start paying close attention to my mileage until the end of June this year. Of course hot summer months = nice mpgs. Now that it's cooling off here in upstate NY I am noticing quite a significant drop in my mpgs. Now I know of course this is inevitable with the colder temps, but it seems like I am losing about 1mpg per 10degree temp drop. Is there a general rule of thumb for ambient air temps and how it effects mileage? Just curious... can't wait for winter! :thumbdown:

[dkjones96]

MY mileage drops when it gets colder but that's because the car runs so much better. On a 20 degree morning I beat the poor car to pieces as opposed to a 105 degree day when it can barely get out of its own way!

[Jay2TheRescue]

Maybe rig up a winter WAI, and remove it in the spring to maintian your mileage?

-Jay

[Erik]

At some point the refineries switch us over to the "winter blend" which yields less mpg

[Jay2TheRescue]

Yes, but a WAI will help soften the impact of winter blend fuel.

-Jay

[KARR]

Try blocking the air flow that hits the radiator. I've tried it once and mileage increased in 10 mpg, on average. I've done nothing that could explain this increase so I suppose it really improves mileage. Last weekend I've made a new "blocker" that covers a bigger area of the radiator.

[SD26]

At some point the refineries switch us over to the "winter blend" which yields less mpg
You beat me to it. Yes, winter blend fuels are different in that they will help the engine start in colder months rather than give the economy of warmer months. There are mandated periods of when those fuels need to hit the distribution chain and then when they should hit the street. I think they hit the marks pretty well.

[Jay2TheRescue]

Yes, a good grille block is usually good for an extra 10% MPG.

[FLAteam]

I've also noticed a drop in my MPGs...but its strange because Scangauge shows that I've been consistently getting 36-40 mpg per trip, yet this last fill-up yielded 34mpg. My cutoff is 4, which is 4 above 0 (my idle TPS) and its uncalibrated.

Could the cold weather be affecting how well the SG is reading my actual mpgs? Should I reset the ECU? I'm thinking seriously for a grill block soon...

[bowtieguy]

no need to wait until winter to do a grill block. i have ~3/4 grill block in temps higher than most. certainly positive or negative(over heating) results vary from vehicle to vehicle, however.

i was thinking of installing a WAI myself.

i'm actually hoping for BETTER FE during winter via limited a/c usage.

gotta add this as well...

in january, i'll think about you northerners while outside in shorts and w/out shoes playing w/ the kids.

[Jay2TheRescue]

I have roughly ~95% block on the beast, and it was fine in 100F + temps.

-Jay

[bsams]

Yeah I would like to install a wai and at least block the upper grille on my 3. The Only issue I have is the car is still under warranty. If anything happens to go wrong in the next 40,000 miles I don't want them to try to put the blame on me if they see I have modified the airbox to accommodate a WAI. Thanks for the replies!

[Jay2TheRescue]

For now do something that is completely reversible. You can save the agressive mods for later when the warranty is out. For example my WAI is nothing more than removing the lid from the air cleaner box and a piece of duct tape. It can be reversed in less than a minute.

-jay

[bsams]

I am beginning to think that it's not all about the weather... a couple weeks ago the local Express Mart switched from Mobil to Sunoco gas. Yes, Sunoco and it's lovely 10% ethanol... yesterday the weather was perfect...mid 70s... and my daily cruise control at 55 ride home from work was not giving me the numbers it normally did with this relatively warm weather... I can't blame the gas switch yet until I fill up again with either Mobil or KwikFill (both gave me consistent mpgs all summer long)... but it really has me wondering...

[Jay2TheRescue]

I'm actually doing pretty good on my current tank of Sunoco, but then again all fuel in this area is E10 so that really doesn't matter. I filled there because it was $3.25/gal which is far cheaper than anything else in the area.

-Jay

[BEEF]

almost 100% grill block on the old cav. just enough room to get my hand in to pop the hood.

that isn't really a fair statement since most of my cooling comes from underneath.

I used plexi-glass that you can buy from lowes. I did this on my wife's car with zip ties. if we ever want to take it off, a pair of dikes (diagonal cutters) will do the job in about 5 seconds. quick, simple, and completely reversable grill block.

also, depending on where your car takes the air from, you may cause a WAI by blocking off some of the grill. my car takes the air from the fender well but my wife's car takes it from behind the radiator. if she were to block off more of her grill, she would yield warmer temps.

all cars are different. pop the hood, see what you have, and go from there.

[Jay2TheRescue]

I took the lid off of my air cleaner, and duct taped over where it sucked the air from the fender. This coupled with the grille block gives me temps of up to 80F over ambient. All this and the grille block and air intake are completely reversible in under 5 minutes.

-Jay

[philip1]

I have a 90% lower block and an 80% upper block on my car with a HOT air intake on the 90* day we had last week my coolant stayed at about 204* and my intake was 140*. No over heating and great numbers for a great huge beast of a car.

[BEEF]

mine has hit 179 IAT but here lately has struggled to get in the tripple digits with 60-70 degree days. the morning is much worse than the afernoon. 40-50 degrees in the morning.

a little warmer lately has pushed me up to 115 or so for IAT.

I am thinking on adding more shielding just for the winter to keep temps higher. I will just have to remember to take it off for the summer.

[bobc455]

At some point the refineries switch us over to the "winter blend" which yields less mpg
In the past, I heard that this happens on September 15 in Massachusetts, although I've been unable to substantiate it. I also can't seem to find out when they switch back to summer blend.

-BC

[SD26]

In the past, I heard that this happens on September 15 in Massachusetts, although I've been unable to substantiate it. I also can't seem to find out when they switch back to summer blend.

-BC
I think that is the start of the modification of the blend, but it is changed also a month or two later. Summer blends start around March? It depends upon where in the country you are too.

[shatto]

1. You might check with your Amsoil dealer. http://www.amsoil.com/products/promos/P.i.GuaranteeWeb.pdf
Their P.I. gas treatment guarantees MPG improvement.
Worth a try, don't you think?

2. I get my gas from Costco because it costs less. Here they get it from; Tosoro, Shell, Chevron, Unocal and Exxon. Whichever is cheaper. It all has the Costco additive package when it goes into the truck. Gasoline that comes out of the refinery is essentially the same.
So, I suggest you fill at a high volume station so you are getting fresh fuel, and pay the lowest cost you can find.

3. And, sometimes you may experience a drop in MPG. This may be because the refinery made too much high octaine and sold it as regular to the station to get rid of it. Putting higher octaine than recommended in your tank reduces MPG.

[theholycow]

Putting higher octaine than recommended in your tank reduces MPG.

I don't think I've ever heard of that. Can you explain it more?

[Jay2TheRescue]

I've heard that before, but I don't think I've ever seen any data to back it up. Personally I feel that all things being equal (Ethanol content, additives, etc) the difference in mileage would be statistically insignificant.

-Jay

[shatto]

Fiat 1500 Station Wagon, Chrysler 300, Volvo DL, Honda Accord, Pontiac LeMans, GMC Sonoma, Dodge Dakota, Honda Prelude.
Simple 4-Banger to sophostocated 4-Cylinder, Original Hemi to....well, I havn't done it with the new Tundra.

At least one full tank of gas on I-5 between San Francisco and Los Angeles or between Los Angeles and San Francisco.
"The Grapevine" is the mountain pass between the LA Basin and the Central Valley and the rise is to 4,000 feet or so, the rest of the trip is nearly sea level.

Dividing miled drove by gallons consumed, gas mileage has always gone down using higher octane than recommended.

[theholycow]

Any guesses why? As I said, I don't recall ever hearing of anybody else who observed that data, but it's interesting if true. It behooves us to find out why; this is the sort of thing that eventually leads to a new strategy, modification, or idea, once we learn the concepts behind the observation.

A first simple guess would be that the additives required to raise the octane dilute the gas, but I doubt that the percentage of additive is enough for that.

[shatto]

Simply; The engine is tuned for the lower octane gas.

[theholycow]

That doesn't tell me anything about why it gets lower FE on high octane gas.

What does that mean, besides compression ratio / timing?

What is it about higher octane rated gas that makes it produce less power in an engine optimized for lower octane ratings?

[BEEF]

this is the explination that I heard, is it true? I don't know.

with higher octane gas, the engine must advance the timing. depending on your engine, your ECU may only be able to advance the timing so far or if you are carburated, you have to adjust the timing. I assume they are talking about the spark plug fire. most modern engines do this automatically and I can't see where it would be an issue.

do I have data to back this up? no

I was having issues with my riding mower and I was asked what kind of gas I put in it. I usually just fill the container when I fill my car and yes I usually put premium in my car. I have been putting regular in it lately because stations around here still don't have premium. they are starting to get midgrade back in stock.

this was just a "for what it's worth" statement. take it for what it is. just something someone told me. true? false? I don't know.

[Jay2TheRescue]

My dad always used premium in his lawnmower and tractor because they were initially built for leaded gasoline. His logic being that regular leaded gasoline had higher octane than your standard 87 octane does now.

[Jetta90GL]

I keep a log of my mpg for all of my vehicles in an excel spread sheet. I log octane for every fill and created formulas to average by each octane. My truck gets about 1 mpg less on 93 octane fuel than 87. On the other hand my 79 yamaha motorcycle was averaging 25.3 on 87 and 42.3 on 93. The sticker on my bike says it requires a minimum of 91 octane Leaded gas.
The way I understand octane is, the higher the octane, the less volatile it is for ignition. That way you will not get pre-ignition in high compression engines.
I would say that the 93 octane in my truck ignites too slow. Which would cause most of the fuel to be burned as the piston is already traveling down, wasting a lot of the power to compress the air/fuel mixture.
I could be wrong, but that is my best guess..

[R.I.D.E.]

Higher octane fuel ignites and burns slower than lower octane. The peak pressure of combustion is lower but over a longer period of time. In engines designed to work with the different pressure curve you can get more power with timing advanced to expolit the longer sustained higher pressure of combustion.

Generally speaking this required higher compression ratios, which in the sixties with leaded fuel approached 12.5 to 1. These same engines would quickly knock themselves into shrapnel with regular fuel.

In a car designed to run on regular fuel, premium is a waste. Many newer engines with knock sensors will run on regular but the timing will be more retarded that the same engine with premium.

My SLK owners manual gives specific instructions to avoid the use of regular except in emergencies. 8.8 to 1 compression with 7 pounds of boost.

My wife uses only regular in her Murano, which also recommends premium. Maybe one of these days I will see if the mileage improves with premium.

This is all my opinion but I think of the combustion properties of premium and regular in the same way as the burning rates of different gunpowders.

Pistol powders are very fast burning, they generally are used in straight walled cases and short barrels. Rifle powders are much slower burning and are mostly used in bottlenecked cases and much longer barrels. If you used the same weight of pistol powder in a rifle, you could easily blow up the rifle.

regards
gary

[theholycow]

:thumbup: Now there's some good explanations. Unfortunately, there's nothing new there. The only new (to me) information is that it actually results in reduced MPG.

[DracoFelis]

Now that it's cooling off here in upstate NY I am noticing quite a significant drop in my mpgs.
Others have already made a number of good suggestions. However, one that hasn't been mentioned yet is tire pressure.

When the air gets colder, you really have to watch your tire pressure and add air if/when needed. The reason for this is that air has higher pressure when its hot, and less pressure as it cools. So even if/when you aren't actually losing any air (and most tires/wheels leak at least some), you will be losing "air pressure" as the outside weather cools. And as has been pointed out many times in this forum, as your tire pressure drops, often so does your FE.

So when the weather starts getting cold, it is important to routinely check your tire pressure and add air (to bring the pressure back up) as needed. Otherwise, you FE will suffer "in the winter" due to the lower tire pressure you are running with.

[GasUser]

Others have already made a number of good suggestions. However, one that hasn't been mentioned yet is tire pressure.

When the air gets colder, you really have to watch your tire pressure and add air if/when needed. The reason for this is that air has higher pressure when its hot, and less pressure as it cools. So even if/when you aren't actually losing any air (and most tires/wheels leak at least some), you will be losing "air pressure" as the outside weather cools. And as has been pointed out many times in this forum, as your tire pressure drops, often so does your FE.

So when the weather starts getting cold, it is important to routinely check your tire pressure and add air (to bring the pressure back up) as needed. Otherwise, you FE will suffer "in the winter" due to the lower tire pressure you are running with.

Yes, tire pressure makes a significant difference and you will loose more than a pound or two when it gets real cold out.

I just picked up a set of plugs and will be changing them today. (30,000 miles on them)

Also I am running full syn fluids in the motor, a/t, both diff's and t-case. I suspect this does only make a very small difference, but at least it has better lube qualities than dino. I read somewhere that it takes 10 miles to completely warm up the entire drivetrain in cold weather. I am not sure if this is true, but I tend to believe it, as it seems logical. Your best FE in the winter will be after your drivetrain is warmed up to normal running temps. I also think the syn fluids help with this.

On cold start up in the winter, I do not let the motor run for 20 minutes. Rather 30 seconds or so at the absolute most. After that I start moving to warm the entire drivetrain at the same time and I turn on the heated seat to the low position and only run it until my butt is warm and shut it off. That is not long and by that time I am starting to get good heat.

I do not run the defrost unless I need it. When you turn on the defroster, your a/c runs to dehumidify the air. All vehicles do this unless it is a really old one. While it works great and keeps your a/c system properly lubed in the off season, I only use the defrost when I really need it. I installed the in-channel type vent visors so I can run with the windows cracked open and not hamper aerodynamics and help with defrost.

I am sure you guys all know this stuff so I apologize for my long post.

[theholycow]

I read somewhere that it takes 10 miles to completely warm up the entire drivetrain in cold weather. I am not sure if this is true, but I tend to believe it, as it seems logical. Your best FE in the winter will be after your drivetrain is warmed up to normal running temps. I also think the syn fluids help with this.

Synthetic fluids are known for reducing friction and better cooling (through imrpoved heat transfer). Those qualities, if true, would make me think that the drivetrain would warm up slower with synthetics (though they would also mean less frictional loss to begin with, of course).

[shatto]

Your Amsoil dealer might have an old brochure with the story of an airport service vehicle, perhaps a fuel truck, from the part of the country where zero degrees in winter is considered warm, that not only had a rear end failure but the oil had frozen to where it actually broke the housing.
Amsoil cured the problem.

[GasUser]

Synthetic fluids are known for reducing friction and better cooling (through imrpoved heat transfer). Those qualities, if true, would make me think that the drivetrain would warm up slower with synthetics (though they would also mean less frictional loss to begin with, of course).

I think that is an interesting thought, but I am not going to go back to dino. In fact, the a/t fluid and t-case fluid from the factory is synthetic per factory spec. All the other fluids I switched myself to synthetic.

[shatto]

I think that is an interesting thought, but I am not going to go back to dino. In fact, the a/t fluid and t-case fluid from the factory is synthetic per factory spec. All the other fluids I switched myself to synthetic.
I think your theory is backward. Synthetics transfer heat better so the gearboxes would heat up to running temperature faster.
On the other hand........so what?

[theholycow]

I think your theory is backward. Synthetics transfer heat better so the gearboxes would heat up to running temperature faster.
On the other hand........so what?

If is transfers heat better, then the items generating the heat would have it transferred away more quickly, and therefore would take longer to warm up (though, importantly, the oil itself would warm up more quickly). If it transfers heat worse (in other words, if it's a better insulator), then the gears would warm up faster.

As for the "so what", I was pointing out that the logic used for "Your best FE in the winter will be after your drivetrain is warmed up to normal running temps. I also think the syn fluids help with this." was broken.

The practical upshot, I'd guess, is that the it takes significantly longer to warm up, with lower friction generating less heat all that better heat transfer draining the heat away from the gears and oil to the housing...but of course, that whole lower friction thing is really what you're looking for anyway. All this talk of heat transfer and time to warm up is in pursuit of lower friction, is it not?

[bsams]

while we are on the topic of lower friction, is it feasible to think that some percentage of mpg is lost as you near a car's need for an oil change? I run full synthetic and change it every 5,000 miles, and I always think I am getting slightly better numbers with nice fresh oil running through it. If it is possible, and not just a million other things that could be effecting mpg at that point in time, it kind of makes me wonder how much the oil is breaking down after 5000 miles. Just a thought...

[itjstagame]

You can test it and see exactly how much it's braking down. I always notice a 1-2MPG difference after a change. Also the engine seems to idle smoother. I can actually tell when it's really in need of a change by a slight increased rumbling or vibration at idle, it's very slight but you can tell it's lugging a bit more.

[MorningGaser]

while we are on the topic of lower friction, is it feasible to think that some percentage of mpg is lost as you near a car's need for an oil change? I run full synthetic and change it every 5,000 miles, and I always think I am getting slightly better numbers with nice fresh oil running through it. If it is possible, and not just a million other things that could be effecting mpg at that point in time, it kind of makes me wonder how much the oil is breaking down after 5000 miles. Just a thought...

I would say the opposite is true. The longer your oil is used, the better MPG you'll get because oil shears to a lower viscosity. I've noticed this because the milage I get from my Yaris is worse at the start of new oil usage, and improves as the oil is "aged". I realize oil can thicken up too, with age, because of oxidation, but on balance, it often shears to a lowe viscosity, and thinner means less resistence for the crank to turn.

[hondaguy72]

A quicker warm up will save fuel, so I agree on the grill block, tires aired up is a no-brainer, but octane is a bit trickier. Modern cars with knock sensors will adjust the max advance during cruise which highly affects mpg. I tend to run mid-grade 89-90 just to make sure my car is always at max timing. I find my mileage to be 7-10% better running the better gas.

[shatto]

while we are on the topic of lower friction, is it feasible to think that some percentage of mpg is lost as you near a car's need for an oil change? I run full synthetic and change it every 5,000 miles, and I always think I am getting slightly better numbers with nice fresh oil running through it. If it is possible, and not just a million other things that could be effecting mpg at that point in time, it kind of makes me wonder how much the oil is breaking down after 5000 miles. Just a thought...

If changing the oil at 5,000 miles is good.....
wouldn't it be better to change it every thousand miles?

[BEEF]

I would think that the cost of the more frequent oil changes would out weigh the gains that you would get from it.

5x the oil changes gets expensive especially when you are talking about synthetic.

that is an oil change every month (or for some of us every 2 weeks)

[koji_kabuto]

colder weather reduces FE because it slows the atomization of fuel. egr valves recirculates part of the exhaust gas into the intake thus reducing emission(unburnt gas) and increasing FE..

it takes more time for water to evaporate during winter than it is during summer, same applies to gasoline

blocking the grills prevents the ram air from cooling the engine bay, creating hot environment for the engine and the air cleaner.. by then, the engine is sucking hot air.

i have my intake located right after the radiator. i use 93mon octane(lowest from where i am) its turbocharged and no ping even at full boost.

octane is over rated i think, most of the cars nowadays have better combustion design(except maybe overhead valves) withstanding compression ratios that were over the limits in the old days

i think you all get 89mon + 85ron /2 = 87

[bowtieguy]

I would think that the cost of the more frequent oil changes would out weigh the gains that you would get from it.

5x the oil changes gets expensive especially when you are talking about synthetic.

that is an oil change every month (or for some of us every 2 weeks)

all else being equal(filter, your time, paying labor, etc), you WOULD save with synthetic. the $10 amsoil series 2000 is guaranteed for 35k miles or 1 year, so MUCH time and/or labor would be saved.

about cold temps...

amsoil has not only the highest flash point, it also has the lowest pour point IN EVERY GRADE. so you're covered hot or cold assuming severe enough cold would slow the flow of dino oil.

[BEEF]

bowtie,

my response was for shatto that said why not change the oil every 1,000 miles vs every 5,000. which would mean you were changing your 5 times as much.

I was stating that the cost of the oil and filters (plus labor) would out weigh the gas mileage of the more frequent changes.

the big selling point in synthetic oils right now is the extended oil change intervals.

my response was intended for shatto and not really at the subject matter at hand.

[bowtieguy]

Beef,

i understand. my thought was in regard to those that reach 3k miles rather quickly and use dino oil. and it just so happens that amsoil can be ~5 times the price of conventional oil.

i drive less than the average driver and still do not look forward to getting under my car twice per year(once for full change, once for filter only).

[BEEF]

I drive more than the average man. I was changing my oil about every 6 weeks (and yes, I was hitting 3k by then). I decided to move closer to work and now it is better but not great. I'd say between 300-400 miles a week. been a while since I checked.