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Xterra SE 4x4 V6 NA
261 Posts
Discussion Starter · #1 ·
In addition to my Hyper-Miling driving techniques that I have posted about to save fuel, I also got to thinking about what my MPG might be if I simply shut the engine off while at a stoplight or other traffic condition that prevents you from moving very much.
Some extreme hyper-milers actually do this and claim to increase MPG by 70%.

I decided not to actually shut my engine off every time I was at a stoplight because this would put an excessive amount of wear and tear on the starter motor.
But I did want to find out what my true MPG would be if I could do that without wearing out the starter.

The first thing I did was find out how much gas my Xterra uses while idling and not moving.
According to the dealership and the service manual the average fuel consumption while idling is 0.6 gallons per hour.
There is a small amount of variation because of things like running the AC, having the headlamps turned on which pulls more power from the alternator, or the engine simply being cold and not warmed up yet.
Anyway, 0.6 gallons per hour translates to 1.28 ounces per minute of engine idling.
This is a significant amount of fuel if you're idling a lot and not moving, such as in heavy city traffic.

To determine the possible MPG I could get if I shut the engine off at every stoplight I counted the seconds I was idling while stopped at a traffic light.
There is a lot of variation between traffic lights. Some are as short as 20 seconds while a few in the town I live in were as long as 90 seconds.

I just completed my experiment today.
In the recent experiment I idled at a full stop for a total of 25 minutes, which includes the times I was stopped at traffic lights and the 5 minutes I let it idle after a cold start.
With 25 minutes idling with an average consumption of 1.28 ounces per minute this meant I consumed 32 ounces of fuel while not moving during this experiment.
The total miles driven during this experiment was 65.35 miles from the last fill-up.
It took 3.09 gallons to top off my tank after this experiment.
The 32 ounces consumed during the estimated idling time is 1/4 of a gallon.
So I took the 3.09 gallons and deducted the 0.25 gallons consumed while idling.
According to the math I consumed 2.84 gallons while actually in motion for the 65.35 miles I drove.
Now dividing 65.35 miles by 2.84 gallons equals 23.01 MPG, and this is city MPG I drove, not highway. My average speed during this experiment was about 35MPH with a high of 50MPH and a low of 20MPH. It also includes my running the AC and using the 4WD for the few miles of dirt road I travel when I go out.

Since the naturally aspirated V6 that is in my Xterra is rated 14 MPG city, this means that if I were to shut off my engine while stopped at a traffic light, combined with my hyper-miling driving techniques, I would increase my MPG by 64.36% above the EPA 14 city, which is not far off from the 70% claimed by other people who do this.

I did some checking and it turns out that most hybrids already have this stop-start system, and in 2020, Toyota, Ford, and BMW have added a stop-start system to their vehicles in an effort to save fuel when stopped at traffic lights.

Maybe one day there will be an aftermarket system available that could be installed in our older cars, because as gas prices rise I am sure all of us want to save money.

Xterra SE 4x4 V6 NA
261 Posts
Discussion Starter · #3 ·
I have a front-drive Chevy sedan with a V6. Some years ago I was a little short on cash and was trying to stretch my gas. I still had to drive 11 miles to work each way, with at least 8 miles on the freeway.

I was turning the engine off with the trans in Neutral when not having to add fuel, such as when descending a slope or when slowing on the flats. At freeway speeds, I was able to go from 18-19 mpg for that tank to around 23 mpg. The car is rated 17 city/ 26 highway and I usually get 20-21 when commuting daily, and 27-29 on trips. But at that time it was winter, so I usually got 18-19 when commuting.

However, it was a lot of extra work, and more than I wanted to endure personally or add wear to my car.

The only time I've ever gotten less than 18 in the car was when I was idling the car while doing something to it to prevent the battery from draining, such as electrical or other mods.

I would assume that the Xterra would be similarly improved. But as above, I won't take on the extra work and the wear on the components.

Still, it's nice to know and discuss ways to stretch the fuel!
Yeah, I remember the gas shortages of the 70s so I've been trying to save fuel with every vehicle I ever owned.
I even went as far as to convert an 81 F150 truck to propane.
The MPG was about the same as gasoline, but back then propane was half the price of gasoline.
Now propane is about the same price as gasoline.
However, propane powered vehicles do last longer.

Back when I was in college in 1984 I actually came up with the idea of an electric hybrid before hybrid vehicles were even thought of by the car makers.
I actually tried to convert an old 1973 Pontiac LeMans to electric.
My original idea was to have an electric motor directly driving the axle with a portable gas generator charging the batteries, but I ran into problems finding the necessary parts and components.
I approached two electric motor companies with my ideas.
One was General Electric and the other was called Baldor Electric Motors.
The representative I talked to at GE practically laughed at me, saying if I wanted an electric car I should buy a golf cart.
I don't know if Baldor is still in business or not, but they were the only one to send me specifications on the electric motors they had.
Unfortunately their electric motors were designed for forklifts. I couldn't find a way to adapt it for use in a car's drivetrain.
Plus, I ran into problems finding batteries. Back then Lithium Ion Batteries didn't exist. The only batteries available with the power needed were the L16 industrial batteries. But those were incredibly heavy. I would have needed a 5 ton pile of them to drive the car 100 miles.
Because of these technical difficulties I gave up.

But then in the late 1990s the first electric hybrids were introduced.
I found it to be a very strange coincidence that these newly introduced hybrids used the same principles of my design. A gasoline engine turning a generator that then powered an electric motor.
Sometimes I wonder if they stole my ideas from one or both of the electric motor companies I approached because in my naivety I told those companies exactly what I wanted to do.
If I had thought to patent my ideas back then I could have made money later. But when you're only 20 years old you don't think of things like that.

Xterra SE 4x4 V6 NA
261 Posts
Discussion Starter · #5 ·
Trains use diesel-electric, which is pretty much the same concept. The old dinosaurs are burned to generate the electricity needed to turn the drive wheels. Were your ideas "stolen"? Not likely, unless you got a patent on them. You may have planted a seed, or the idea may have come to them from somewhere else entirely.

I read a Popular Science article (or series of articles, I don't recall which) when carburetors were still in common use. I learned and started applying a number of their ideas and have been getting better mileage for decades. It's just a matter of knowledge being made more common, which is what you're doing by sharing what you've learned.
I did have the ideas when the only electric vehicles available were golf carts. I only say stolen because I did explain my ideas to those electric motor companies when I was trying to find the motor I needed for the project and all it would take is one person working for one of those companies to present the idea to a major car maker.
And that is why I said I wished I had patented my ideas back then because I might have had a case when the electric hybrids came out.

If you recall there was the story of Robert Kearns who invented the intermittent wipers back in 1964. He patented the design and approached the major car makers, but they declined and even laughed at him. Then in 1969 a similar system started showing up as an option on new cars from Chrysler, Ford, and GM. Kearns sued them for patent infringement starting in 1972 and after a number of appeals finally won a $30 million judgment against the big three in 1992.
They made movie about it called "A Flash of Genius".

So I'm just saying that if I had thought of patenting my ideas for an electric hybrid car back in 1984 I might have had a case, because if their design was anything similar to mine they would have owed me. That's why now most companies do patent searches to make sure a product they have an idea for has not been thought of before, because paying off the patent owner is cheaper than lengthy litigation.
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