1. Autos

Your suggestion is on its way!

An email with a link to:


was emailed to:

Thanks for sharing About.com with others!

Questions and Answers

Plymouth Neon: Gasoline To Diesel?

Q. Hello, I am on a quest to get the ultimate bang for my buck. I want to get the most out of my fuel. I drive a 1999 Plymouth Neon 2.0 liter SOHC. I usually get around 23-27 MPG driving city/highway mix to and from work in a week.

Plymouth Neon: Gasoline To Diesel?

However I was thinking, I know that people convert gasoline and diesel engines to LPG, and I have even seen someone take a NO2 setup and replace the NO2 with H2, then mixing then injecting that into a diesel engine, making it very fuel efficient.

This last idea is a little out of my league. I am not mechanically inclined that much, although I do enjoy projects and tinkering with my car.

So my question is this, is it possible to convert a gasoline engine to diesel, and would that help of fuel economy. I am not looking for a power increase (it would be nice, but come on I drive a neon) just better MPG that what I get. I have looked at products like the Tornado, and have even redirected my air intake so that as I drive I actually force air into my system, still through my filter, this actually gave me another 2 to 3 MPG.

The only things that I can think that I will need to do is replace the spark plugs with glow plugs, drain the fuel tank, maybe a different filter (probably not) and refilled with diesel.

Please let me know if my assumptions are correct, and if you know of anyways I can (cheaply, yes I am cheap) improve my MPG for my little mouse driven machine. No I do not depend on the power of mice, I say that because the engine whines like a mouse when I reach high RPMs.


A. An interesting idea, one General Motors tried about 22 years ago. It was a miserable failure.

There are a few fundamental differences between a gasoline engine and a diesel engine. I wrote an article on The Diesel Engine you should read.

First, and probably most important, is the compression ration. The compression ratio in a diesel engine is, at least, 21.5:1. The compression ratio in your 2.0 liter engine is 9.8:1. Why such a high compression ratio in a diesel? Well, a diesel uses the heat of compressed air to ignite the fuel. In a gas engine that is done with spark plugs.

To correct this, you would need to install a crankshaft with a much longer throw to develop, at the very least, a 15:1 compression ratio. For your engine, there is no such thing so you would need a custom made crankshaft.

That's the first reason it will not work.

The fuel in a diesel is injected directly into a pre-chamber where the glow plug is housed and where the actual combustion takes place. The fuel in a gasoline engine is injected into the intake manifold, drawn into the combustion chamber and ignited.. If you inject fuel into the intake manifold of a diesel, the engine would not last very long.

To correct this, you will need to modify the heads to accept a pre-chamber, glow plug and diesel fuel injector.

That's the second reason it will not work.

Fuel injectors and fuel pressure are next. The fuel pressure in your 2.0 liter engine is about 49 psi. Much too high for diesel injection. Fuel pressure for a diesel ranges from about 5.0 psi to about 19 psi.

To correct this you will need to replace the fuel pump with one of a much lower pressure, a mechanical fuel pump is the best due to it's lower output pressures. So, you will need to find someplace to mount the fuel pump on the engine and figure out how to drive it.

That's the Third reason it will not work.

Now we need to inject the fuel at the proper time. For that we need Diesel MFI Pump. The injection pump is a high pressure rotary type pump that is controlled by the Powertrain Control Module (PCM) and meters, pressurizes, and distributes fuel to the injector nozzles by way of high-pressure lines. Now this needs to be mounted on the engine and tied to the crankshaft via a timing belt.

To correct this you will need to get a Diesel MFI Pump for a four cylinder engine. Then it needs to be mounted on the engine and tied to the crankshaft via a timing belt or other timing device.

I could go on but I will give you one more reason. A diesel puts out a great deal of pressures, compression in the 350 psi range and combustion pressures four times higher than a gasoline engine. To handle these pressures the gaskets, head gasket in particular, have to be able to withstand these pressures. The head, block and engine bearings have to be much heavier to withstand the pressures as well.

Oh yeah, the suspension will need to be beefed up to handle the extra weight of a diesel engine.

General Motors did not take these things into account when they converted their 350 gasoline engines to 350 diesel engines.

Now this can be done, as anything can with enough money and time, but the cost of the conversion will run into many thousands of dollars and you will have to drive the car for 2,764 years to start to get a return on your investment.

If you want a diesel engine, you would do much better to buy a vehicle with a diesel engine in it. My 1983 Mercedes Benz 300D turbo diesel with 225,000 miles on it still gets about 45 mpg and it is stock from the factory.

Want to squeeze a few more mpgs? Read: Gas Saving Tips and Suggestions

Additional Information provided courtesy of AllDATA

Back to Index

© 2003-2004 Vincent T. Ciulla

©2017 About.com. All rights reserved.