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Old 08-02-2005, 12:27 AM   #1 (permalink)
gal's Avatar
Diesel in a gasoline engine

A friend of mine from New Zeland rented a car here in Norway, and unfamiliar with the different gasoline ratings, she asked the gas station guy what pump to use. Now, these guys are usually not the brightest crayons in the box, so my friend ended up filling the tank with diesel using a funnel the guy gave her. Of course the car stopped after 10 meters.

The other day I ran into an argument as I told this story to some friends. They all agreed that it was a good thing that she didn't rent a diesel and then filled up with gasoline, cause the engine would blow for sure. I'm not too sure about this, cause I know that diesel engines are built for higher compression than a gasoline engine. My guess is that the gasoline (95 octane is the norm here) would ignite too early. The engine won't run since the pistons would probably not be able to pass the top due to the early combustion. Am I right?
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Old 08-02-2005, 01:33 AM   #2 (permalink)
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I'm guessing that nothing would happen because the is no spark in the diesel engine pistons, so the gasoline would just sit there.
Then again I have no real idea about cars so I am now waiting to be corrected.
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Old 08-02-2005, 03:19 AM   #3 (permalink)
Location: Outside Providence
I'm not entirely sure exactly what would happen, but I do know that any engine not running on the fuel it was designed for will not perform at it speak. That's not to say it won't run, as I have seen an old ford truck run on a 50-50 mix of diesel-gasoline, but it ran very roughly. The gasoline woulkdmost likely combust because of the heat caused by the massive amount of compression in a diesel engine. I know this is way off topic, but when you say normal, are there 3 diferent grades like there are here or is there only 95? And if there are more than 1, is 95 the highest octane available? I believe here the grades are usually 87, 90, 93.
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Old 08-02-2005, 03:28 AM   #4 (permalink)
I know for sure that you MUST NOT start the engine once you accidentally filled gasoline in a diesel engine. The tank has to be pumped empty and the engine cleaned.
At least here, in Europe, I think the diesel pistons are bigger so they donīt fit in a gasoline tank.
But maybe I am mixing this up, itīs bad either way.
Btw, I saw a gas station clerk telling a lady, who accidentally put gas in a diesel that "thatīs not that bad..." Well, if you donīt care about a $2000 bill, itīs not bad.
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Old 08-02-2005, 04:20 AM   #5 (permalink)
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The grades we have are unleaded 95, 97 and 98 octane. The latter contains "lead replacements" for older engines designed for leaded gasoline. High performance cars often use 97.

The nozzle for diesel is wider, hence the use of a funnel
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Old 08-02-2005, 05:12 AM   #6 (permalink)
as far as I understand it, and I know a guy who did it - complete crack-monkey but that's a different story - Apparently you're ok in most newer vehicles even if you do start the car with Diesel. It'll die almost immediately, and be expensive to fix, but you won't need a new car.
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Old 08-02-2005, 05:23 AM   #7 (permalink)
Ok, I got curious, and did a little looking.

Here: http://www.straightdope.com/mailbag/mdieselvsgas.html

Below is an excerpt of the article:
"What happens when you use gasoline in a diesel engine? Either something expensive or something very expensive. Since gasoline is designed to be resistant to self-ignition, gasoline in a diesel engine either won't ignite or will ignite at the wrong time. Some diesel engines run leaner than gasoline engines (meaning that the air-fuel mix has a higher proportion of air than a gasoline engine). That increases the chances that the gasoline won't ignite and that unburnt fuel will be sent into the hot exhaust system--where, ironically, it could ignite, leading to possible exhaust damage. Even if you avoid that disaster, you can expect to pay $500 to drain the fuel tank, clean out the fuel lines, and refill the tank with diesel.

Some types of diesel engine use the diesel fuel as a lubricant for the fuel pump (remember, it's a fuel oil). It's said that running gasoline through such a pump could lead to serious damage or failure, turning a $500 repair into a $750-$1,250 one.

Trying to use diesel fuel in a gasoline engine also has unpleasant consequences, but generally not as dire in terms of damage to the fuel system. Depending on the proportion of diesel fuel relative to gas in the tank, a gasoline engine will either run poorly or stop altogether, necessitating another $500 trip to the repair shop for draining and flushing. A couple of old grease monkeys at the shop I used to work at claimed that their "super high-compression" gasoline engines of the late 1960s could easily switch between gasoline and diesel fuel with no problems, but I tend to think they spent too much time inhaling fumes from the carburetor cleaning tank."
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Old 08-02-2005, 05:31 AM   #8 (permalink)
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Location: Use the search button
Ah, a wonderful thread to return to!

I missed you guys.

As a member of the military, we have thousands of people that are not "The Brightest crayons in the box", and having said that, when you are really tired and the only thing to distinguish the fuel types is a coloured band on the Jerry Can, you can mix up fuel types. It is a common mistake.

Diesel in a Gas engine: Yes, it is unfortunate, as your filters and spark plugs and everything else will be horribly gummed up. The mechanic chastizes you quite soundly, you feel shame and your co-workers never let you forget.

"Hey Ben, remember that time you put diesel in the Commander's Jeep and he had to walk for 10k? That was funny as hell."

Gas in a diesel engine: There is a big problem here. Yes, the above poster is right when they say that there is no spark and diesel engines run on compression. Gas engines run on about 10-12:1 compression, and diesel starts combusting at about 30:1. (Expert mechanics help me out on the numbers here please)
So when the piston starts to compress on the up-stroke, the damned gas starts to combust before it (the piston) reaches the proper height. Then you start to bend really important things like valves, cams, rocker arms, and the piston rods themselves. You have also introduced a fuel with nearly zero lubrication properties (relative to diesel, anyway) and will also burn the piston rings. Did I mention this is happening at about 3 times the fuels normal compression environment? Shit starts to explode, and it is nasty.

While the diesel engine is burning the last bit of natural fuel in its fuel lines and introducing the devil's blend you have unfortunately poured in the tank, there is about 3 seconds when the engine starts to rev at a very high rate and it sounds really cool like a race car and nothing at all like the normal "dang-bang-dang" of our friend diesel. This is the amount of time you have to realize your mistake without frying the WHOLE ENGINE!

This is where you have a really mad mechanic, and the story is not so funny.

"Ben, remember the time when you blew up the Commander's truck, and he made you give him a piggy-back ride until a replacement arrived?"

Hey, if you are impressed with my memorizing pi to 10 digits, you should see the size of my penis.
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Old 08-02-2005, 06:05 AM   #9 (permalink)
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Location: In my angry-dome.
I think 8.5-10:1 would be more realistic for modern gasoline compression ratios, and 15-16:1 for diesel. Otherwise sounds good. Results would be vehicle dependent. I've heard of people using gas in a diesel car, driving a while before realizing the problem, cutting back to diesel and getting many miles without unexpected problems. Can't do it much good though, and it's more common to hear some piece of the engine failed. The early GM gas-to-diesel setups would have to be very angry since they were just repurposed gas engines.

Adding a little gas to diesel isn't uncommon for truckers, say 5% in winter to help starts and prevent gelling.
There are a vast number of people who are uninformed and heavily propagandized, but fundamentally decent. The propaganda that inundates them is effective when unchallenged, but much of it goes only skin deep. If they can be brought to raise questions and apply their decent instincts and basic intelligence, many people quickly escape the confines of the doctrinal system and are willing to do something to help others who are really suffering and oppressed." -Manufacturing Consent: Noam Chomsky and the Media, p. 195
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Old 08-02-2005, 11:37 AM   #10 (permalink)
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Good stuff Thanks, guys.
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Old 08-03-2005, 07:27 PM   #11 (permalink)
Simply put, gas is explosive and diesel is not.
Oddly enough, high quality gas, is rated on how unlikely it is to burn (er, explode)...
High quality diesel, on the other hand, is more likely to burn.
A gas engine wouldn't run on diesel unless there's enough gasoline to ignite the mixture...in which case, there'd be a lot of smoke, and would probably damage O2 sensors and maybe catalytic converters. If the mix was less than 15% diesel, I don't think it would cause any harm.
Gas in a diesel, probably would ignite, er explode. Probably do bad stuff...
And yes, modern diesel engines would have issues. The pumps and injectors are under as much as 65,000psi, even the diesel needs added lubricants to keep the parts functioning well.
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Old 08-09-2005, 12:18 AM   #12 (permalink)
I worked on a lot of GM diesel trucks at my old job...specifically light duty (1/2 ton to 1-ton pickups) with the 6.2L or 6.5L turbo diesel V8s...the newer Isuzu "Duramax" engines are a nightmare but don't get me started on those.

There have been a couple trucks in for a fuel system drain/flush due to people putting gas in diesels....and no, the engines didn't rev uncontrollably.....and the bill wasn't $500 either because it only pays typically 2-3.5 hours labor to do that at $90/hr (Canadian) and there aren't any expensive parts involved. Maybe it would cost more in a diesel car like a VW or whatever, I don't know because I've never done them and I don't know what's involved.

We did have one, that the oil lines were leaking oil into the incoming intake air going through the turbo, causing it to rev to 7,000+rpm...take out the key and you're holding it in your hand...still does it and runs exclusively on its own oil. Another time, I saw a guy in a cube van with a 6.5L drive it in without the oil pan on it (and therefore no oil) because the steering was too hard to turn without it running. Those GM 6.5s are tough as hell and it's too bad they replaced them with the dumbax.
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