Fuelish Endeavors

Grumpy Bear · September 17, 2022

My wife drives 10 to 20 mph faster than I do as a general rule...but....miles divided by hours over nearly 300,000 Km on each of our vehicles shows she averages about 36 mph (the national average) and I 42 + mph. Guess who spends less on fuel? Guess whose trips take less time? Guess who has fewer drive train issues and has lower tire/brake cost? No brag, just 7 years of facts played out on this forum for which every reader has had a front row seat.

Begs a few questions. Notice that wasn't one of them?

Oh, you have bags of money and don't need to worry about how much you spend on gas and maintenance.

GREAT!

Then you won't be bombing this tread with a basket full of stupid.

Bye!

KARNUT · September 17, 2022

My wife and I liked to drive slow fast. We have curvy roads that are fun in sporty vehicles. Her car is a sports sedan. You can lean in a little without drawing attention. Vehicles have been a sport to us with budget in mind. Her overall expense has been more efficient even though I get the better mileage. I anticipate and idle less. She’s had one car going on 12 years and one going on 23. I’ve had many more. As a hobby it’s been a cheap endeavor. I’m always looking. We’ve saved in other areas. We enjoy our rides, within reason.

garagerog · September 18, 2022

IMO nothing will increase your city mpg and brake longevity like anticipating traffic lights and nothing teaches that better than learning to drive with a manual transmission. Unfortunately with the dearth of MT's over the last couple of decades the current generation and those going forward will not learn this skill. One thing I can say for my wife, she will never have to worry about rusty brake rotors!

Grumpy Bear · September 18, 2022

Work with the Laws that govern this Universe

How do you process the idea of the amount of money you spend on fuel?

We've already excused the "I don't care" crowd.

1.) Cost per unit time? $$$$ per year i.e.?

2.) Cost per mile?

3.) Volume per unit distance? Gallons or Liters per hundred miles or kilometers.

4.) Distance per unit volume? Miles per gallon or kilometers per liter.

The last three are different ways to quantify the relative value. The first is an absolute measurement. Either way to improve and verify that improvement, that is spend less for a fact, you need an accounting method and a tracking mechanism. Collect and analyze data. You also need to have a basic understanding of Newtons three laws of motion.

Just a suggestion. Don't use your DIC. Some are deadly accurate and some are off a bunch. Collect and record actual data.

Edited September 19, 2022 by Grumpy Bear

garagerog · September 18, 2022

Grumpy, I'm afraid I'm guilty of relying on the DIC in my wife's Equinox but I only really check it when I'm the primary driver on road trips, not on her around town driving. Road trips for me involve gassing up at different stations and using different pumps, so there's that lack of consistency needed for actual data. I don't use the DIC mpg for any type of bragging rights, but more as another input to my sensory ones on how well the motor is running. I really need to step into the 21st century and get a scanner capable of recording live data, but my wife says my middle name is procrastination and I hate to keep proving her wrong all the time.

Grumpy Bear · September 18, 2022

45 minutes ago, garagerog said:

Road trips for me involve gassing up at different stations and using different pumps, so there's that lack of consistency needed for actual data.

That is where statistical analysis is helpful. Dampens the noise of variation in pumps (and drivers) and identifies variations in seasons. Separates causes and identifies effect. Long enough trending will even show the need for services and modify 'habits'. Programs like EXCEL make the difficult easy. Tackle all that a bit later.

Grumpy Bear · September 21, 2022

A sampling of speed vs time for two different settings.

Zero in on the second chart. Two zones. First looks like 45/50 was the target and the second perhaps 55/60 and yet the average is but 48.3 mph. Over the course of a tank the average is more like a mix of these two charts but the point is the average is below the target. How much below has a HUGE impact on the measured mpg for the entire tank.

As I mention in the first post wife drives (target) quite a bit higher than I do and yet my average is higher than hers which results is boost in fuel efficiency.

Today I had Dizzy out on a 250 mile ride where I ran about 8 mph slower, 45-48 than my usual and yet for the tank the average speed was 42 mph. Same as when I drive 53-55. The result of that tank was a new personal best for this SUV.

Her 60 to 75 mph target nets an average of 36 ish and 25 - 27 mpg.

Let that mull around awhile in the gray matter. I averaged the same speed driving slower and netted higher mileage.

Best mileage happens when your average speed is a high percent of your target speed.

SMOOTH

Dizzy's 5 mile steady state mileage vs speed. Mileage is vertical axis and speed is horizontal axis. I had to travel to a spot about 100 miles away to collect this data over the course of two attempts. Very good roads most flat that are very lightly traveled laid out in an equilateral triangle of 8 miles per leg near the Mississippi River in Rock Island County. Hot days over 85 F with winds under 5 mph. No A/C.

https://onlinepubs.trb.org/onlinepubs/webinars/180314.pdf

No matter what speed you decide you must drive that speeds fuel economy can be improved with driver behavior modification.

Be SMOOTH......

Grumpy Bear · September 22, 2022

Newton says in law one that a change of state requires an outside force and in law two that this force equals mass times acceleration. In law three he states the this force has an equal yet opposite counterpart.

Force is the result of fuels energy acting upon the vehicle to produce motion. This energy is stored in the mass of the vehicle. That energy will be spent the question is on what and in what. Some will be spent on the equal and opposite reaction of road resistance. Tire and bearing friction. some will be spent on overcoming the resistance of the air it travels through. the excess moves the car down the road.

But some is spent or actually wasted in the braking system. Every time you use your brakes you waste the fuel moving the car down the road to heat. In an ideal world you would let off the gas and allow the vehicle to coast to a stop or off the gas and coast down to the oncoming lower speed limit. The first is hard to do in traffic but the opportunity does present itself at times. The second isn't as hard as one might think. I drive on cruise control most of the time and have mapped in my mind nearly every inch of road within 175 miles of home base on nearly every roadway that can be traveled. I know exactly when to drop out of cruise and when to tap it back in to 'land it on a pillow'. Hills are your friends when slowing down and when speeding up. Less energy is spent accelerating going down the hill that up. Use that fact to your advantage.

You will be amazed how many speed reductions are spaced so that tapping out on the higher will have you tapping in at the lower sign. Not perfect and weather has an effect but do it as a practice and you will find your marks and it will be come second nature. It will reward you with better mileage and fewer brake repairs and tire replacements.

Most people drive like they are a Pulse Width Modulated digital signal. Either on the brakes or on the gas. Waiting until they get to within 50 yards of a stop sign to brake and brake hard then on the the throttle hard to 20 over the limit...rinse and repeat. Be analog in nature and habit.

SMOOTH

Smooth slow is faster than abrupt quick and has a huge impact on operating cost.

customboss · September 22, 2022

Well stated Grumpy. In auto road racing I did, smooth was fast.

garagerog · September 22, 2022

Couldn't agree more with this more Grumpy, I always practice the SMOOTH when traffic allows, I alluded to this earlier when I mentioned anticipating traffic lights. Your mention of using hills to your advantage is a good tip, when traffic allows I also make my lane changes gradual and on rural freeways with light traffic I will do a gradual lane change to diamond a corner decreasing the corners radius. Probably results in infinitesimal mileage improvement, but may help tire scrub a tiny bit. Back to the hills, brings me to freeway rest stops and how some states do a better job of locating them than others. Back in 2005 I drove my 71 SS Chevelle cross-country from Wa. state to SC and across the Wyoming state line on I-80 flat land Nebraska had located their welcome center rest stop on top of a knoll, whether it was natural or man made IDK, but it allowed the 18 wheelers to de-accelerate easily and conversely accelerate much quicker than normal to easily blend in on 80mph I-80. I gave the unknown civil engineer that designed that a mental tip of my hat. On the other hand here in SC we have a rest stop on I-26 between Columbia and Charleston that's located on a long uphill grade so merging back on the freeway safely in my wife's Equinox with the anemic 2.4 almost requires taking it up against the rev limiter, I now avoid that rest stop. One of the highest compliments I've received in my life is when my late MIL commented to me on a round trip road excursion to Atlanta what a smooth driver I was. Not only does the SMOOTH improve mpg and vehicle longevity, but more important at least to me, you and your passengers will arrive at your destination more relaxed and not on edge. Long live the SMOOTH!

Grumpy Bear · September 24, 2022

Hot and Cold

You're running down the road fully warmed up and your vehicle will get 35 mpg. (blue line) But how does it behave before that?

The yellow solid line is MPG vs Units of Distance and it follows a thermal constant. In this graph it took about 13 units of distance to reach 35 mpg. The area under the curve is the yellow dotted line. In this case 29.7 mpg. This is how your truck behaves mpg wise dead cold.

The solid read and dotted red are the curves drawn from a stop after being fully warmed. Once hot, it takes a shorter distance to get the same average...and because it does, the area under the curve is a higher percent of the the perfect number. In this case 32.9 mpg.

When you are on long trips this the reason you second tank is always better than you first.

Hopefully you can understand that if you distances are shorter you never reach 'perfect' and the area under the curve will fall even further. Short hopping to less than hot is a mileage killer and also a fact of life for most.

In stop and go driving you stitch together a combination of hot and cold, stop and start. sitting in bank line or drive in to get even a worse number.

I'll link this to viscosity in the next post.

Edited September 24, 2022 by Grumpy Bear

Grumpy Bear · September 26, 2022

There is viscosity and then there is viscosity

Last post I talked about the effect oil temp has on MPG and I think everyone knows oil temp is a proxy for viscosity. The hotter the oil the less resistance it has to flow. The easier a thing moves threw it.

Cold oil is like wading chest deep in wet cement. Warm oil like wading in water and hot oil like wading in air in an illustrative way. Not in an absolute way. More effort = more fuel used.

The differences are magnified greatly under 75 F as you can see in the chart below.

This time of year you really see a hit in the fuel usage and more so if your commutes are short. Even 5W20 is 5X more resistant to flow at 25 F than it is at 125F. A change from 10W30 to 0W30 will have more positive effect on you fuel economy than a move from 5W30 to 5W20.

That said not every 5W30 behaves the same. Nor does every 0W20 behave the same. I've shown how temperature effects the mpg and how SAE grade does and how SMOOTH is a player.

Next is 5W30 vs 5W30 choices.

Grumpy Bear · September 27, 2022

Take note that the cold performance numbers for each grade are a MAXIMUM value.

Take note that the HTHS numbers are a MINIMUM value.

Take note there is no spec for 40 C viscosity (there is an expected range but not a spec)

Take note that ONLY the 100 C viscosity has an upper and lower limit.

There are literally 5W30 oils whose low temperature performance will meet the 0W spec and whose HTHS will meet the specs of a 40W. There are also oils whose numbers 'just' meet the specs. It's a marketing wet dream.

There are oils that exceed specs primarily on base oil selection, as @customboss noted and there are oils that must use additive chemistry to meet those specs.