Wednesday, September 1, 2021

Making Stiff Blends At The Gas Pump

I have experimented with ethanol conversions and stiff ethanol blends in cars,  tractors,  and lawn equipment,  since 2006.  I did this with quite a variety of equipment.  The two full E-85 conversions were a 1944 Farmall-H farm tractor,  and a 1973 VW (air-cooled) Beetle. 

The vehicles I used for stiff blend research included that same 1973 VW Beetle,  a 1960 VW Beetle,  a 1995 Ford F-150 pickup,  a 1998 Nissan Sentra sedan,  and a 2005 Ford Focus sedan.  These were not modified in any way from stock for the blend tests or for routine use. 

The ’73 Beetle was restored to its E-85 conversion,  while the 1960 Beetle was left stock,  when these two vehicles were re-mothballed.  The rest are still in service.

I also have been using E-30 to E-35 blends in two lawnmowers and a wood chipper,  all 4-stroke,  all completely unmodified.  If there were a problem with this,  then after 15 years,  I would know about it.  There is not. 

The automotive manufacturers,  and the 4-stroke lawn and garden equipment manufacturers,  went to ethanol-compatible materials many years ago,  not long after the advent of unleaded gasoline.  The high aromatic content in the unleaded gasolines was just almost as harsh to the older materials as the ethanol.  (Methanol is far worse yet.)

The 2-stroke manufacturers,  and the boat motor people (and the old-time aircraft manufacturers),  did not update to ethanol-tolerant materials.  They are the source of all the tales about how “bad” ethanol is for engines.  And for them (and only them) it is true,  precisely because they never updated their materials selections!  These materials actually go “bad” rather rapidly on ethanol-free gasoline,  just because of the high aromatic content.  The ethanol in an E-8-to-E-10 ULR just causes these already-vulnerable materials to fail only a little faster.

The net result of all this is that I can recommend stiff blends up to E-35 maximum,  as drop-in fuels in any spark-ignition automobile,  no modifications required.  You will not be able to tell the difference in power,  or in fuel economy,  between these blends and straight gasoline.  That is because the natural scatter in your mileage data from tank to tank is larger than any effects of the blends

If you do this in a 4-stroke lawnmower,  do it with a not-so-stiff blend nearer only E-20.  If you do an E-35,  the over-simplified carburetor may need its screws reset. It won’t idle right.  The idea was “drop-in” fuel.  I’ve used E-35 in them,  but not-so-stiff is more of a drop-in fuel.

In the cars,  you are essentially trading increases in energy conversion efficiency for the decreases due to lower heating value (this was also the conclusion of my PhD dissertation,  which was based on earlier work I did with ethanol in piston engine airplanes). 

You will see cleaner spark plugs and a potential increase in your oil change interval,  because your oil will not darken as quickly.  Those of you who do your own repairs and take the cylinder heads off,  will find combustion chambers and piston faces that are cleaner of carbon deposits,  than any you ever saw that were operated on gasoline.

Really old cars,  from before the switch to unleaded fuels,  might be vulnerable if the factory-stock carburetor and fuel pump parts are still installed.  However,  these were replaced in most such vehicles long ago,  due to simple age,  and normal wear-and-tear.  The replacement parts were made from ethanol-compatible materials,  starting many years ago.

How To Do This

To do this reliably,  you need to “calibrate” the marks on your fuel tank quantity gauge.  When you pull into the filling station,  you need to be able to read the gauge and know how many gallons it will take to fill you up.  I leave that determination to you;  everybody has a different vehicle,  and needs to do this for themselves. (See Update 9-5-21 below,  at end of article.)

 Once you know how many gallons you are going to put in,  all you need to do is figure out how many of those gallons need to be E-85,  and how many need to be unleaded regular gasoline (ULR).  That is quite easy to figure,  as explained below.

Be aware that the maximum ethanol (“max eth”) content of E-85 is 85%,  and that of ULR (which is a nominal E-10 material) is maximum 10%.  The minimum ethanol (“min eth”) content of the E-85 product in wintertime is actually about 70%.  Most of the time when I tested ULR,  I found its ethanol content to be less than maximum,  at about 8%.

There is a volume ratio R of ULR to E-85 that is associated with the blend strength you want.  This is depicted in Figure 1.  Use the “max eth” curve data for this,  to limit just how strong your blend will be.  R = 2 will get you a blend strength between E-35 (the “max eth” curve value) and E-29 (the “min eth” curve value).  R = 6 will get you a blend strength between E-21 and E-17.  R = 4 will get you a blend between E-25 and E-20. 

Figure 1 --  Blend Number vs Volume Ratio R = ULR to E-85

Once you know your desired value of R,  divide your intended gallons-to-fill by R+1,  to get the gallons of E-85 to load.  Your fill-up gallons minus your E-85 gallons is your ULR gallons to load.  It really is that simple!  Most of your cell phones have a calculator,  with which you can make these calculations,  standing right there at the fill-up pump. 

Don’t exceed a “max eth” blend strength of E-35!  That works even in winter,  although you may have to start the engine twice (or even 3 times),  before it sustains.  That’s the maximum practical blend strength for cold starting.  (It is still short of where mileage and power suddenly drop,  which is just about E-42.)  You can use a lower blend strength,  but do not go higher!

To aid your selection of an R value,  the max eth and min eth data,  from which the curves in the figure were plotted,  are included here as Table 1.  Use the max eth data and your max desired blend strength to set R.  Then use the min eth data at your R to find your minimum blend strength,  which is effectively a winter value with typical winter product formulations.

Table 1 – Data From Which The Curves Were Plotted

Related Articles (all are located on this site)

There is a navigation tool on the left side of this page.  Use the list below (jot them down on scratch paper).   Click on the year,  then on the month,  then on the title. 

12-15-09….Red Letter Day:  Ethanol VW Experiment Complete…[ethanol ’73 VW]

11-12-10….Stiff Blend Effects in Gasoline Cars…[’73 VW,  ’60 VW,  F-150,  Nissan]

11-17-10….Nissan Mileage Results on Blends…[Nissan blend experiments]

2-12-11…...“How-To” For Ethanol and Blend Vehicles…[converting the ’73 VW,  and more]      

5-5-11…….Ethanol Does Not Hurt Engines…[general]

6-12-11…..Another Red-Letter Day…[re-mothballing the VW’s]

5-4-12……Energy Storage: Batteries vs Unpressurized Liquid Fuels…[related data]

8-9-12……Biofuels in General and Ethanol in Particular…[related data]

Update 9-5-21:  How to Calibrate Your Analog Fuel Quantity Gauge

You need two things:  a fuel mileage log,  and a set procedure during fill-up to fill the tank to the same mark every time.  There is no way to properly calibrate the gauge without these two things,  so just make up your mind to do it!  You can only do this with an analog gauge that uses a needle with a scale of marks.

Fill it to the same mark (such as 3+ click-offs of the pump;  pick a number and live by it) every single time!  That takes it somewhere slightly above the full mark on the gauge.  Log the gallons filled and the odometer reading every single time.  EVERY SINGLE TIME! 

Between fill-ups,  watch your gauge reading as you roll up miles traveled.  Record the odometer reading as the needle locates at every mark,  down to about the ¼ (or possibly 1/8),  tank marks on the gauge.  There is no other way to do this,  so just make up your mind to do it!  Take care and watch the needle closely over long time baselines,  as turning accelerations,  throttle accelerations,  and braking decelerations will cause it to misread temporarily. 

Do this for at least 10,  and preferably 20-or-more,  tanks of fuel.  That way you get statistical reliability.  Then reduce your data.  Here is how: 

The mileage difference between two fill-up odometer readings is the miles traveled on the gallons loaded at the current fill-up.  Divide miles traveled by gallons loaded,  for the average mpg on that tank.  Do this to about 4 significant figures (example:  20.57 mpg).  Use the corresponding mpg value for each tank in the calculations that follow,  not some overall average. 

The mileage difference between the fill-up odometer reading,  and the odometer reading at the full mark,  is the miles traveled on the overfill quantity.  That miles traveled divided by the average mpg for that tank is the estimated gallons of overfill above the full mark.

The mileage difference between the full and ¾ tank marks is the miles traveled on the top quarter of a tank.  Those miles divided by the average mpg for that tank is an estimate of the gallons in that top quarter of the tank between those marks.  (You will find that a “quarter of a tank” isn’t really 25% of a tankful.  Surprise,  surprise!)

The mileage difference between the 3/4 and 1/2 tank marks is the miles traveled on the second quarter of a tank.  Those miles divided by the average mpg for that tank is an estimate of the gallons in that second quarter of the tank between those marks.

The mileage difference between the 1/2 and 1/4 tank marks is the miles traveled on the third quarter of a tank.  Those miles divided by the average mpg for that tank is an estimate of the gallons in that third quarter of the tank between those marks.

If you have the data (if not,  skip),  the mileage difference between the 1/4 and 1/8 tank marks is the miles traveled on that part of the tank.  Those miles divided by the average mpg for that tank is an estimate of the gallons in that portion of the tank between those marks.

If you do this data reduction at every fill-up,  it is not so onerous.  But either way,  it must be done!  Once you have this data for 10 to 20+ fill-ups,  then average the estimated gallons for overfill-to-full,  for full-to-3/4,  for ¾ to ½,  for ½ to ¼,  and (if you have the data) for ¼ to 1/8 tank.  Those will be the best estimates you can make. 

Now your gauge is “calibrated”.  If you add these things up,  then you know statistically how many gallons it will take to fill,  from each mark,  starting at zero for the overfill condition.

One fill-up simply won’t do it!  You need the statistical reliability from many fill-ups before you can trust this data!  10 is the utter minimum,  and it is not very good.  You really need 20+.  Trust me,  I’ve done this many times with many vehicles.  Done right,  it really works. 

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