where are all the gas saving devices that are invented?

Because they don’t exist.

I’m sure Allen you have heard of the OIL Company that buys them all..Well that’s not exactly true..For the most part I could make an engine that would get at least one hundred miles to the gallon of diesel pretty easy .To do it we have to give up power steering , air conditioning lights at night or night driving at all and heaven forbid uphill climbs of more than about 2%..You see to do work it take energy and because the INternal combustion engine,jet,turbine anything we have is a terrible energy converter..Oh i see where we might get HYdrogen cells at a mere 20K extra per car..to make the hydrogen it takes about 1.3 times as much electricity as you get from the Hydrogen and to make the electricity we burn coal and the lose is just as bad so Hydrogen is clean alright but to get it in your car you added the same number of steps as you did to burn gasoline. right now if there were CNG operations were you could actually take advantage of them the USA has enough Nat gas to provide every car in America for the next 12-15 years. OPEC would have a coronary and for me I would love to see them try to eat the oil they have..In the early 90 I was really lucky and had a short project working on a precombustion chamber on a nat gas diesel conversion system. It worked really well the problem was there was not way to carry CNG on the truck and no way to get the bottle filled on the road and lastly it costs a lot . The good part was though it raised the average mileage on a 500hp diesel (caterpillar v8) from 5.6 mpg to 7 that’s a big difference let me tell you..All that equipment is in mothballs now.In some building hid in the country.. I assure you there was no oil company that bought us out ..WE WERE the OIL company..Anyway bottom line is if you play you gotta pay.. So for mileage you give up all the comforts…That’s just the way it is…Have a good one….from the E…

They are produced. You can find them all over the internet. These devices are heavily advertised, preferable using free news for credibility. Problem is, none of them offer much improvement, so while a few suckers will buy them, they can’t get mass sales. Were someone to make such a device, he could sell it to GM or Toyota for big bucks, so they could meet fleet mileage requirements.

When you study thermodynamics in college, you find that modern engines are very limited by the theoretical maximums. So, car makers improve aerodynamics, reduce car weight, use thinner oils, better combustion chambers to improve mixing, better ignition systems, more efficient transmissions and tires, etc, for tiny incremental improvements in mileage.

Everyone would like to believe that some “magic bullet” will let our cars burn water instead of gas, or get 100 mpg, but it just isn’t in the physics. No such thing as a free lunch …

Despite the media reporting such things, and conspiracy theories that abound, you can be certain that simple add-ons that claim a significant improvement in fuel consumption are a scam. Things I have seen mostly offer some sort of modification to the air intake, fuel delivery part of the system. They are often based on some claim like better or smoother burning. Tell me what car doesn’t burn fuel smoothly. The only ones that don’t have a fault, not working properly. What about actual improvements enthusiastically reported – maybe these are misunderstandings, but more likely outright lies. Try to follow one up.

As for the media, they are journalists, so why would they have any special ability to judge what is a scam or not? Some of the present crop of scams are things that generate so called HOH gas. These are based on some supposed magical property that makes the hydrogen oxygen gas mixture improve the normal fuel. There is often mystique associated, so if it doesn’t work, you must not have followed the instructions. Another is a “turbo” thing put in the air intake, more like a flow spoiler. It is supposed to swirl the air so the fuel mixes better, and what! Even works with diesels! I have seen such things promoted using top racing drivers etc. I guess this demonstrates some of them are just as incapable of judging as a journalist then.

The ways to improve fuel consumption are to reduce losses, or improve efficiency. This starts with the driver, how the vehicle is operated, choosing to use lower acceleration, lower speed, correct gears etc. This is not always practical of course, so it is only done when appropriate. Tire pressures help, drive with the windows up, air-conditioner off, no unnecessary weight on board, etc.

The losses in the engine that can be readily improved in older cars are mostly due to air flow, from the intake, through the engine and then the exhaust. Increased compression ratio improves the efficiency of extracting energy from the fuel, but is limited by the fuel in how far you can go. Better tuning helps. However most modern cars already have a reasonable balance of airflow, compression and accurate tuning, so there will not be any dramatic improvement by playing around with these.