Finding Average Temperature for a Tank

[Bruce]

One other tip that can make things easier...if you enter an end date before your start date (e.g. the previous year) and hit "Go", both date fields will be reset to your start date.

This can be helpful if you're doing a bunch of tanks at once, working back in time, because it transfers your start date to your end date.

[Ernie Rogers]

Okay, I'll ask the dumb question--

Why do you want to know the temperature?

[pumaman]

Originally Posted by Ernie Rogers

Okay, I'll ask the dumb question--

Why do you want to know the temperature?

Because the outside temperature greatly affects your gas mileage. You get worse mileage the colder it is.

[Ernie Rogers]

Originally Posted by pumaman

Because the outside temperature greatly affects your gas mileage. You get worse mileage the colder it is.

Okay, let's take that as an impirical fact. Why do you suppose that is?

1) Rolling resistance is greater at low temperature?

2) Air density increases?

3) Cold intake air lowers combustion temperature?

4) Energy density is lower in winter fuel? (True for diesel, at least, probably also for gasoline.)

5) Shocks and springs are stiffer?

What do you think? How much variation is there with temperature?

Counter-considerations--

1) Cold fuel is more dense

2) No air conditioning

Ernie

[HemiSync]

Empirical or not, it is a fact. Here is a nice description of why it is worse including some interesting sources.

9 reasons why your winter fuel economy bites!

[gershon]

The title of this thread seems to imply there is an optimum temperature to drive at. I'm thinking it's at warmer temperatures, but I don't know. Does it really make a lot of difference if you have synthetic oil and fuel injection?

Gershon (I'm new at this.)

[Right Lane Cruiser]

You are correct -- there is an optimum temperature. Keeping track of the average temperature with your tank data will help you find it.

[pumaman]

Regardless of what else you do, your FE will be worse in the winter, assuming you don't live in San Diego or Key West.

This is because your engine is not at it's optimum efficiency until it warms up. When the ambient temperature is colder, it takes longer for the engine to warm up.

Check the Mileage Logs of some of the folks who live in the northern states. I live in Missouri, and I went from around 41 mpg last summer to around 36 mpg this past winter. Now I'm back up to the 40s.

As next winter approaches, you will see desperate hypermilers begin talking about grill blocks and engine heaters.

[pdw]

Originally Posted by pumaman

Regardless of what else you do, your FE will be worse in the winter, assuming you don't live in San Diego or Key West.

This is because your engine is not at it's optimum efficiency until it warms up. When the ambient temperature is colder, it takes longer for the engine to warm up.

Check the Mileage Logs of some of the folks who live in the northern states. I live in Missouri, and I went from around 41 mpg last summer to around 36 mpg this past winter. Now I'm back up to the 40s.

As next winter approaches, you will see desperate hypermilers begin talking about grill blocks and engine heaters.

True, it's Easier to attain a peak/optimum vehicle operating temperature in southern Florida's hot environment. But once it is warm, an engine faced with Northern windchills still begins to shed the unecessary heat as it does in a heatwave.

We pay for that cooling just like we pay for the AC-cooling. If we are talking about moderating tips like the grill or the plug-in .... those are just the top of the iceberg (so to speak) on what is possible to preserve/keep that kind of energy cost low when the sourroundings are frigid.

I'm almost afraid to list the means I've employed to make it though the winter.

[alvaro84]

I'm thinking of covering a part of the radiator at winter to warm the engine faster. Now the mornings/nights are in the 10-15C range and it doesn't seem to measurably hurt my FE, but last time temperature went close to 0C my FE dropped drastically: at that time I did 3-3.3L/100km (71-78mpgUS) by somewhat careful, conservative driving (light right wrist, using the highest possible gear, keeping speed limits, keeping as steady speed as I could, trying to avoid unnecessary accelerating and braking), but around freezepoint I couldn't do anything better than 3.5L, and even had a 3.9L/100km (60mpgUS) tank (it had a 70km city ride at -6C with a 2 stops - the 'season closing' ride on 31st of December )...
I'm curious what next winter has for me.
I'll keep an eye on tyre pressure (~sidewall max, don't want to go higher on 2 wheels, already higher than BMW's recommendations), but I think I'll give up on FASing down our street and the next few ones, I'm afraid I'd reach the freeway with a cold engine. I'll also have a bit higher load on the battery, my heated gloves eat up more 2 amps (got them this spring).

edit. on the original topic: I usually just guess. I ride both early mornings and afternoons, virtually every tank.