New tires = 3.4% larger (MPG includes adjustment)


Anyone else notice a drastic drop in these colder temps?

Hey there.

How much bigger (what size?) I was thinking of picking up 265/75/R16 Nokian Hakks (studded) on Monday, 'cause the ice / freezing rain here has finally forced me to do something. I was going to go up to the 265 from 245 which will worsen my MPG right..

Do you have a ScanGauge?
And what additive is it that they (gasoline refiners) would add? Would it be ethanol/methanol as an antifreeze, but which has a lower energy density thus lower MPG?

Thanks

Dante :wink2:

 

Hey there.

How much bigger (what size?) I was thinking of picking up 265/75/R16 Nokian Hakks (studded) on Monday, 'cause the ice / freezing rain here has finally forced me to do something. I was going to go up to the 265 from 245 which will worsen my MPG right..

I just went up a size to 267/70-17 which is about an inch taller diameter that OE. For your case it depends on the rolling resistance and weight of the tire. To get the correct mileage you will just need factor in the larger tire ratio.

Do you have a ScanGauge?
And what additive is it that they (gasoline refiners) would add? Would it be ethanol/methanol as an antifreeze, but which has a lower energy density thus lower MPG?

No scangauge. I would assume ethanol although they say they don't use it. My buddy with the Jeep didn't notice a drop like this in mileage last year.

Do you warm your truck up before driving off in the morning?? To give you time to scrape the windows? That could account for the drop..

Good point. There has been a few days where I had to scrape the windows while the truck was running. But I wouldn't expect that to = a 5MPG drop.

 

Do you warm your truck up before driving off in the morning?? To give you time to scrape the windows? That could account for the drop..

 

ethanol in the gas kills gas mileage.... i hate winter but then again gas prices have dropped also... 1.75 here in Ellensburg, WA!!!!

 

I filled up last night... 75L and it was only $50 :thumbsup:.

Here it was 72.2cents/L. I remember when it was in the 40's.

 

Mine has dropped, but not as bad as yours. Over the summer the truck did 19-19.5 mpg with my normal driving, and about 21 on a couple longer trips. Now I do about 17 mpg or so.

 

Mine is down about 2.5 mpg. It happens every year. At least gas is cheap right now.

 

Its definitely the added ethanol in our winter fuel I noticed the same huge decrease from my regular filling station. But remember that they may have different ethanol content in different fuels here and I know here that they are not specifying what % ethanol is in your fuel. I use my truck for work and by switching gas stations I was able to take my mileage from 14.5L/100 (16.2 Us mpg) to 11.5L/10 (20.5 Us mpg) Also my mileage is with 500lb weight in the box of the truck and me (200lb) I also have a 2.5" lift and E load range 265/70/17 tires. My mileage is about 60% hwy and 40% stop and go off road
I don't know about your truck but if i'm careful about how i accelerate and drop my speed by 5km/hr it makes a HUGE difference in my mileage. Also just for comparison with the same tires and stuff on my truck I had a half a cord of wood in the back of my truck and got 9.3L/100 (25.3 Us mpg) This was achieved over a 450km hwy trip in the summer about 26 deg C cruise on other than big hills and the a/c was on too. In that 450 km i only used 42L of fuel. Learn to baby the throttle and you'll be amazed what that thing will do for MPG

 

Check the pump for a sticker stating the fuel has been oxygenated (alcohol added).

 

I think it has less to do with the winter gas than just being fucking cold.

Engine takes a lot longer to get to full operating temperature, posibbly never getting there. Running defrost to clear windows, which also runs the A/C to dry the air prevents full operating temperature and uses gas. Startup mix is very rich at 15F and gets much worse as temp drops.

Differential and transmission oils are thicker and also don't get very warm.

Air is denser, wind resistance goes up, snow on the ground greatly increasing rolling resistance.

If your trips are usually short MPG will plummet, if you drive long distances the effect is since everything has a better chance of warming up.

My mpg goes from 37 summer to 26-29 depending, and I'd atribute 1mpg due to winter gas. That drop is with essentially no time spent idling to warm the engine, which is just a wast of gas and would make matter much worse. Someone getting 18mpg would probably expect 17.5 on winter gas if driven in the summer.

 

I doubt its to do with warm up or any of that I park my truck in a heated garage. So all of my fluids/engine all of that are a the same temp as a cool morning in the summer.

 

Winter gas

Worthywads, all good points.

We have at least one gas station here (Mohawk - "Mother Nature's Gas" haha) who openly state their gas may contain up to 10% Ethanol - and that's all year round. I should do a test of their gas vs others in the summer comparing L/100 km.

I wonder, in the winter, does their gas just stay the same, since it's already spiked with ethanol year-round?

Dante:wink2:

 

besides the ethanol crap, there is the closed and open loop system to consider. 6shooter i'm sure would know better but when your truck is cold it is in a closed loop i think using more fuel. when it warms up it becomes an open loop. also when your truck goes over 3000 rpms it becomes a closed loop. i may have the closed/open loop backwards. closed loop uses more fuel.
imo- it sounds like they added the 10% ethanol to the big tank of fuel but never shook/stirred it up and you may have gotten a huge amount of the ethanol. that would definitely explain it if your last tank happen to have mainly ethanol.
ethanol has around 2/3s of the BTUs that regular gas has so it takes a lot more gas to create the same amount of explosion in the engine. thats why if you have a vehicle that were converted to all ethanol it would have to get bigger fuel pump, fule lines, and injectors.
anyway feel free to correct me in anyway you see fit or just add on.

 

I saw single digits in the Tundra last year :lol:

 

I'll post here what I posted on Tundra Solutions about this:

(in response to 12-14 mpg in cold weather)

That is quite normal in cold weather. I usually average around 15 mpg. There's an inverse relation with the density of the air and temperature in that the lower the temperature, the higher the density. The ECU is programmed with this in mind, and modifications are made to the base fuel maps when it is running in closed loop. To counter the extra density in air, the ECU injects more fuel. What you get in return in an increase in power, but also lower efficiency (in terms of MPG, the engine is actually running more efficiently, hence the increase in power). Read below for the effect of ethanol on MPG.

----

The rest of your problem can be attributed to oxygenated gas and ambient temperatures (assuming your driving style and speeds are similar between fillups). When the AFR sensor detects extra oxygen (from the ethanol) in the exhaust, it tells the ECU to inject more fuel to burn it off (but the fuel is oxygenated, so it really doesn't help anyway). A loss of 2% in MPG is nominal for E10 blended fuel. Summer and winter blends typically use a 10% blend. All modern ECUs are programmed with this in mind.

Low ambient temperatures contribute to the loss in fuel economy, as do seasonal winter blends. The ambient temperature affects air density, and the blends change fuel volatility. Winter fuel blends do NOT add more ethanol, as this would cause hard cold starting since ethanol is harder to burn. What they do change is the volatility of the fuel. Summer blends are made to resist vapor lock due to their reduced RVP (Reid Vapor Pressure), while winter blends can use a higher RVP since temperatures are lower and the risk of evaporation is also lower. RVP is the measurement of vapor pressure of gasoline at 100 degrees F. Winter blends use more butane in the mixture to raise the RVP. All gasoline blends must be below 14.7 psi, or atmospheric pressure to avoid gasoline boil and evaporation. Summer blends are mandated at 9.0 psi or lower. Sometimes winter blends can cause issues when the temperatures stay high. Since winter blends have a slightly higher RVP, it can evaporate faster in high temperatures, creating vapor pressure in the fuel tank which can quickly reach atmospheric levels of 14.7 psi, thus causing the gasoline to boil and creating vapor lock.

Some other things to consider:

Open loop vs. Closed loop operation

WOT and acceleration (this is why city driving, and stop and go traffic are terrible on MPG) are open loop programs meaning the ECU does not take any external sensors (other than the MAF sensor) into account during the fuel injection process. This means NO adjustments are made to the base fuel maps. The base fuel maps are determined by engine RPM and intake air volume only. Cold starts are open loop, which is why you'll often smell gas in the exhaust from the engine running a bit rich. During engine cranking, the ECU reverts to batch fire fuel injection where ALL injectors fire to ensure enough fuel is injected for starting, especially cold starts.

Idling and steady speed cruising are closed loop programs after the coolant temp reaches above 120 degrees F. This program takes ALL sensor inputs into effect to adjust the base fuel maps. Closed loop operation can decrease or increase fuel injection amount by determining sensor readings (this is where you lose MPG from oxygenated fuel - 10% ethanol blends). However, this is also where your engine will run richer or leaner depending on elevation (air density again) and air temperature. Typically, engines run leaner in the summer due to the reduced amount of oxygen molecules in the air. This effect can also be seen when rising in elevation, say from sea level to 10,000 ft above. Just as it is harder for you to breathe going from sea level to 10,000 ft, it is also harder for a normally aspirated engine to breathe too. Forced induction motors see less of a drop since the air is pressurized, but there is still a loss. Closed loop operation will also cut the fuel injectors off when your foot is off the gas pedal.

You should also consider using a 0W-20 or 5W-20 oil if you aren't already using it to reduce pumping losses and achieve higher oil pressures faster (less engine wear) in cold temperatures.

I average 22mpg during 100+ degree summer days, and 18mpg during colder winter days (41-60 degrees). However, this average drops to 16mpg if I drive in temperatures below 40 degrees (winter nights) for a long period of time and if I use 4WD in snow (of course). Tire air pressure is 35psi and I'm relatively smooth on the throttle. When getting on the freeway, I still punch it and achieve good MPG figures due to steady cruising (cruise control helps).

 

Same here...although I've only lost about 1-2mpg, which isnt' that bad. My driving is primarily consistant from tank to tank and my MPG's have been consistantly 18-19mpg this summer. I noticed the difference immediately from one tank to the other.... now I'm getting between 16-17.5mpg with winter fuel.

There's definately something 'different' with the gas mixtures. My husband hasnt' noticed a difference in his Acura MDX, but then again...he doesn't track his MPG like I do. He also runs 89octane all the time. I always use 87 but this past tank, put 89 in. I'll use 89 for a couple tanks and see if things change at all.

 

Here in WI thanks to the EPA :jerkit: there is 10% in the gas year round.
Not only was my mileage better with out it ,but the truck ran better on
just straight gas.

 

iv been getting better mileage here in arizona as it gets colder...drive only freeway and was getting 24-25 mpg now im getting almost 27

 

Less A/C?

 

Re: detailed post by 91MR2quickNA

Thank you!

 

You're welcome, but since it's so long, you're probably the only one who read it. I did bold the important things for people with short attention spans.

 

Mine has dropped a similar amount here in Anchorage, AK.

Some of it is due to me using the remote start to warm up in the morning---and extra 10 minutes of idling here.

Also, I put BFG AT 265/75/16s on it, which bumped the tire size from 265/70/16--about 1" difference.

Since, they don't do much of anything to the roads here, I've run it in 4WD off and on almost daily.

 

Are you factoring in the larger tire size into the mileage when you do your calculation?

I honestly don't really care about the crappy mileage so I'm not going to adjust my driving style to save MPG.

I'm really just seeing how normal this drastic drop is just in case there could possibly be something wrong with the truck.

 

Winter gas mixtures - are different because of how gas acts in cold vs warm temps. Liquid gas doesn't burn, the vapors do. In warm climates, the liquid is more volatile (turns to a gas/vapor/evaporate). In cold climates - gas is less volatile and less likely to evaporate. So - they put stuff in it (someone mentioned oxygenated) to help it be more flammable in colder temperatures.

 

Never below 20mpg all summer. Add cold, snow, more 4wd use, winter tires, & winter fuel... 17. Same thing every year. At least no E10 here.

 

what are you shift points? I've tried a few variations shifting below 2K and about 2.5K but can't keep it consistent for a full tank.. That's pretty good though, if it's highway or city?

 

every year it goes down. maybe if i get bored later, i'll post my 3 years of data.

i can live with the mpg, but it annoys me when i let off the clutch and it takes a extra bit of time for it to actually engage.

 

I get 17 to 18 MPG in the summer, and 14.5-16 MPG in the winter. KC, MO with an '05 DC SB 4x4 SR5 & 4L V6. I have only observed 18 MPG once.

When it is below freezing, I get the worst mileage. I think it runs richer when it's cold to warm up. I let mine warm up for about 2-5 minutes, but only have a 15 minute drive (6 miles) to work so.......

 

Interesting thread. I am impressed by the data you fellow Tacoma owners have collected over the years!
Nice work. Access Cab 4x4 6 cylinder. Summer I see around 16 to 17 which seems slightly lesss than most of you all. And right now I am seeing 13 to 14 mpg. I honestly don't pay attention to Ethanol ratings. Maybe I'll start checking it out.....
just thought I'd add my 2 cents of mileage results....which are unfortunately less than you all

 

My last fill up was 12.12MPG :lol:.

And right now I am seeing 13 to 14 mpg. I honestly don't pay attention to Ethanol ratings. Maybe I'll start checking it out.....
just thought I'd add my 2 cents of mileage results....which are unfortunately less than you all

Nope it's not less :headbang:

 

Same here, I was getting 18-18.5MPG up until a month ago or so, now I get around 16-16.5MPG.

 

My last fill was 14.32MPG. There was some hwy involved and I started driving around in 4 in the city. Not sure if that made any difference.

 

It can be detrimental depending on how fast you're going. The ECU locks up the transmission in 4th gear at around 50mph. It does it variably in 5th, but it's usually around 40mph. Locking out the torque converter is always beneficial for efficiency.