Adding Diesel to gasoline - Page 3 - Fuel Economy, Hypermiling, EcoModding News and Forum

Christ · 11-30-2009, 12:14 AM

I agree, it doesn't make sense any other way... The thermal efficiency of the engine doesn't change at all, so that doesn't add up unless it's from the higher BTU content.

tjts1 · 11-30-2009, 01:23 AM

Ya this doesn't add up. Every case I've seen of mixing diesel with gasoline has been a total disaster. There was a case recently where the nitwit at a local gas station filled up the 91 octane tank with diesel fuel. About a dozen cars unknowingly filled up with diesel, drove about a mile and broke down. Eventually the tow truck driver that was picking up all these cars off the side of the road put 2 and 2 together and called the gas station to turn off that pump.

http://www.youtube.com/watch?v=CvjrT5mRj_U

Christ · 11-30-2009, 01:26 AM

Wonder if there was something more to that story? Maybe it had something to do with FI vs Carb? I think every vehicle I've put it in was a Carb'd vehicle, so I can't vouch for FI... it could have clogged the fuel filter, etc... Diesel is useful as a spark ignited fuel, though, that's not to be questioned.

tjts1 · 11-30-2009, 01:41 AM

The vast majority of cars built in the last 25 years have EFI of one form or another.
Here is the original story.
Cars die after diesel flowed from high-octane pumps at San Rafael gas station - Marin Independent Journal

Christ · 11-30-2009, 01:46 AM

Can't say, really. I've done it on carb'd cars, and never with EFI, that I remember. At least not in full or large quantity. Maybe a gallon or so at a time, in my Sunbird (Pontiac 2.0OHC non-turbo).

I've run 2-cycle gas at 32:1 in my Civic, as well. Smoked a little bit, but it smoked normally, so I can't tell if it was from the fuel or just normal smoke.

As little regard as I normally have for my vehicles, I've added all sorts of things to the fuel, just to find out what would happen.

Of course, if you add diesel, the engine will run differently, and EFI fuel pumps aren't really designed to lift and pump diesel properly, nor are the injectors designed to flow it properly. Adding it to gasoline is a big difference from just using it straight.

I have to assume that those owners (of rather expensive cars, which normally means that they're not too up to date on their car knowledge) just noticed that it wasn't running like it normally did, and pulled over and called a dealer/mechanic etc. I'm sure they were more afraid than rational at that point.

I'd also never trust a dealer to tell me what's wrong, since they're usually known for including things that have nothing to do with the actual repair.

lindsayjim · 11-30-2009, 04:18 AM

I would not try this blend in anything except a cylinder direct fuel injection system.

In an unmodified spark ignition engine designed for gasoline, which utilizes an unmodified carbureted fuel system or a manifold injection fuel system, the mixture will go too lean and likely result in explosive ignition. Explosive ignition will quickly and seriously damage the engine.

In the experiment underway, the engine has an unmodified cylinder direct injection fuel system and an unmodified OEM computer controlled ignition advance system utilizing a knock (preignition) sensor.

To date, there are no adverse affects.

Christ · 11-30-2009, 11:09 AM

Quote:

Originally Posted by lindsayjim

I would not try this blend in anything except a cylinder direct fuel injection system.

In a carbureted system or a manifold injection system the mixture will go too lean and result in explosive ignition. Explosive ignition will quickly and seriously damage the engine.

In the experiment underway, the engine has an unmodified cylinder direct injection fuel system and an unmodified OEM computer controlled ignition advance system utilizing a knock (preignition) sensor.

To date, there are no adverse affects.

My experience points otherwise, but your mileage, and opinion, may vary.

lindsayjim · 11-30-2009, 02:41 PM

Point taken, see edit for clarification. I don't want anyone to try the wrong equipment set-up and damage their engine.

Hopefully your trial with your Caravan will result in an overall savings similar to mine. I look forward to reading your result.

Christ · 11-30-2009, 02:43 PM

If I do it in the Caravan, it will be just before I take it off the road to do a diesel conversion with my OM616.

The results will be inconclusive, at best, but a generous change should show that a difference can be made.

some_other_dave · 11-30-2009, 07:15 PM

I've seen film of someone who filled their 911 with diesel instead of premium unleaded. Truly staggering amounts of smoke were coming out of the tailpipe...

Did anyone else notice the "takes several minutes of idling to warm up" statement? Sitting stationary with the engine running is generally very bad for fuel economy. For shorter trips, I imagine that would eat up all of your fuel savings, and then some.

-soD