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What happens when you add diesel to your gas ?

4.6K views 23 replies 15 participants last post by  bigjoe460  
#1 ·
The reason why I ask is I did this one time only because I was low on gas and there was lots of diesel at the place I was at. I only put a couple gallons in so I could make it to a gas station. What I noticed was it seemed to cruise at highway speed a lot better ( less throttle).
I was just wondering what it would do for the octane level. I'm guessing it would lower it, but I'm not sure.
Anyone know, or ever have to do this before?
Steve
 
#2 ·
Yep, by accident! What I noticed was the truck (351M) ran sluggish and blew huge amounts of white smoke on deaceleration. Also the diesel washed past the rings and thinned up the oil. The oil level actualy increased. This was with about 60/40 mix gas to diesel. After I changed the oil a couple of times and kept diluting the fuel mixture untill it was all gas the truck ran way better. It seemed to clean things out although I wouldn't do it again on purpose! FredR
 
#3 ·
I had a customer do that one time on a new engine I built for him, he felt silly when I found the problem. It made the engine run very lean and it smoked white and ran awful. He had about a 50/50 mixture, it was strange, you could hold the choke shut and the engine would run you could see "gas" down in the intake with the engine off, like it was flooded. I figured out what was wrong when I got a little of the "gas" on my hand and it felt oily. He drained the tank and it fixed the problem, what he did with that stuff, God only knows!
 
#4 ·
Ive also seen people do that by mistake too, put all diesel by mistake,don't run worth crap. But after I did it on purpose, I actually did it quit often afterwords. I would put 5 bucks diesel and 30 gas. It did let some smoke out when I let off the gas, but otherwise seemed to be better than straight gas. Thought mabey I was getting a better seal on the rings, but not sure about that either.
Diesel ignites under compression so I thought mabey you might be able to run a higher CR ?
Probably a really stupid question, but I was just thinking about it.
Thanks Steve
 
#5 ·
King-snake said:
Yep, by accident! What I noticed was the truck (351M) ran sluggish and blew huge amounts of white smoke on deaceleration. Also the diesel washed past the rings and thinned up the oil. The oil level actualy increased. This was with about 60/40 mix gas to diesel. After I changed the oil a couple of times and kept diluting the fuel mixture untill it was all gas the truck ran way better. It seemed to clean things out although I wouldn't do it again on purpose! FredR
I know a fella that believes in pouring a little #1 diesel in his oil right before he changes it. He will pour a quart or so and run the engine for a while and then drain. I don't know if it helps anything, nor have I seen him actually do it.
 
#6 ·
The "emergency" gas that many chain stores sell in gallon containers to keep in the trunk for an emergency is a mixture of Mineral Spirits and Kerosene so, it will get you to the nearest gas station however, using a lot of it is bad news; the volatility of fuel oil is not as high but, the same goes for it, although it smells a whole lot worse.
 
#8 ·
DaveMcLain said:
I had a customer do that one time on a new engine I built for him, he felt silly when I found the problem. It made the engine run very lean and it smoked white and ran awful. He had about a 50/50 mixture, it was strange, you could hold the choke shut and the engine would run you could see "gas" down in the intake with the engine off, like it was flooded. I figured out what was wrong when I got a little of the "gas" on my hand and it felt oily. He drained the tank and it fixed the problem, what he did with that stuff, God only knows!
I've run plenty of 2 cycle premix fuel thru my pickups, usually I threw whatever was left in the 5 gallon can into the partially full truck after riding, never a problem, until one time we were almost out of gas and put around 5 gallons of 40:1 fuel in my brothers van, did exactly as Dave stated above, it did however get us to a gas station. Never tried deisel.
 
#9 ·
I work in an oil refinery and let me say, in my opinion, this is a very bad way to doctor gas. By definition diesel is low on octane, as this is too light a component to burn correctly under a diesels compression. We measure diesel in cetane and actually by how low the cetane level is, as in diesel has to be heavier than cetane.

As far as the ill effects in gasoline:
it is more viscous(thicker) so your fuel metering is now FUBARed which means you air fuel ratio is a mess. And since there is more carbon to burn in diesel it would need (way) more air anyway.

diesel is dirtier than gas. Sulfur and such compoundes are in there that you don't want running through you gas motor.

Since you gas engine doesn't operate in the right heat range expect a residue to be left behind in the combustion chamber, and expect plugs to foul.

Also this fuel is going to coat the backside of your intake valve, not good for air flow over a period of time.

From the engineering side of the fuel, we basically have 30ish specs that we have to meet for a multiple of reasons, performace, environental, deposits left after combustions, etc. Diesel doctoring will wreak havock with them all.

If none of those are reasons enough then consider this: before gas prices shot through the roof a couple years ago our profit margins were a lot tighter. Diesel was less valuable than gasoline. If there was anyway we could have blended diesel into gasoline we would have for the profit difference.

If you wish to doctor gas for Octane or high CR in the garage, consider Toluene. This is the "rocket" fuel that F1 cars use to use when they were running 50+ psi of boost. its octane rating is 114 and does not have the corrosion problems that alky has. It is an aromatic like benzene so it is carcenogenic similar to benzene (lesser so though). This can be purchased at your hardware store in the solvent section.

And what ever you do, do not put diesel in a modern motor with all its electronics. The long term damage from that is more than i care to right out.

hope this helps, but at the end of the day hot roding was built by pushing the conventional rules beyond their breaking point, but considere yourself warned.
 
#13 ·
yeh, i was waiting for the comments about us price qouging SOBs in the oil industry. Let me just say, there is plenty of blame to go around for the price of gas/diesel: crude price, taxes, refiners profit, and retailers(gas station) profit, and of course there is always the old addage that you charge what the market will bare. i am just an engineering pawn in the game.

To give you an idea, our profit margin on a gallon of gas is between 20-35 cents. However, we sell billions of gallons of this stuff. the reason oil companies are making more money is the margin used to be 5-15 cents a galllon. By the way, the goverment make more money per gallon than we do.

Diesel always goes up in winter since counter to gasoline, heavy distallate need rises in the winter. Kerosene, home heating oil, fuel oil, and diesel share many of the same molecule/components and therefore puts more of a premium on distallates.

all i can say is, sorry about gas prices.
 
#15 ·
diesel

Diesel used to be a by-product of making gas. + as such the price was reflected as it was.
Fast forward to 2007. We now have ULSD. (Ultra Low Sulphur Diesel.) The cost of refining ULSD is very costly. Cammin mentioned gov't taxes. Yes, the local, county, state, + feds tax diesel like no-ones paying attention to it. We're talking mega bucks here. Like ULSD costs about .63 to 1.15 a gallon to make. (depending on your location in the US.) The rest of the price lies in TAXES!
Now; if all these taxes went to repaving our roads, I wouldn't complain. But, this tax money goes every which way your gov't decides it should go. Mass transit. Bike trails. Car pool Lanes. Ports + Piers, Airports. Yep. That $15-70.00 gov't fee on your air ticket wasn't enough to cover the cost of the concrete.
Anyway, by far the biggest cost of Diesel, is purely taxes! Makes me sick!
firewoodtruck
 
#16 ·
Well I guess I won't be putting diesel in my motor anymore.
Cammer? I'm interested in the solvent you mentioned, what is it's purpose? And does that really work as an additive?
And yes the goverment gouges us in every single way, never mind all the fuel taxes. How about booze, smokes,income tax etc etc.
Thanks for all the feedback guys! Funny how one topic can lead to another. Steve
 
#18 ·
"octane boosters"

a member had PMed me about Toluene as an octane booster and i sent him the following:

"Toluene blends with gas ,on an octane basis, in a linear fashion. So in example if you made it half and half you would just average the octanes (93+114)/2=103.5 or 93*.5+114*.5=103.5

to get 110 octane would require about 80% toluene 0.8*114+0.2*93=109.8

the only real issue you have with this much toluene is low volatility. The very properties that keep preignition down in an engine (octane) make it less volatile. Therefore, starting may be difficult with this much toluene (80%) since there won't be much light ends in the mix. But once started, drivability should be fine.

The biggest key to any octane booster is cheap availabilty. if you have acces to something then that makes it better than the next ingredient that does the same thing. If i end up having to splash blend my own gas for my engine, toluene is what i will use (to get 94-95 octane)

By the way, many people use aviation gas for its high octance 110ish, but one thing many people don't know is that there is still ALOT of lead in this gas. This is always a welcome thing for any valve train under hard use. Of course you have to keep this out of cat converters and modern sensors.
hope this helps. "

Also, the cheapest octane boost you can get per gallon is the 93 at the pump. I know this sounds fishy being as i work in oil, but i was doing the math myself and unless you have an inside deal on some other chemical you can't beat a 6 octane boost for 20 cents.

As far as diesel goes: a measurable chunk of the price difference between it and gas is capitalism. simply put, the market will bear it for now. The others are ceratinly taxes, fuel oil season, ULSD upgrade cost (our plant spent $150 million in upgrades to meet the new regs). Of course the really bad thing about the cost is that you pay for it at the pump, and EVERYWHERE else. Remember, everything you buy is shipped using diesel and those cost are passed to us.
 
#19 ·
Octane booster...

Thanks Cammer. One more quick quick question. I read somewhere that the over the counter octane boosters that are used, like 104+, barhdal,etc. bond with the Toluene molicule in the gas to raise the octane. If this is true could you in fact raise the octane higher with a 50/50 mix of toluene/gas and measured amount of booster compared to 94 octane and the required amount of booster? Example, A tank full of 94 octane and 8oz. of boostergives you, say 98 octane but a tank full of 50/50 split and the same 8oz. of booster would give you a higher octane, like 110 or 112. If this is true do you know what the ratio of Toluene, gas and booster would be required? Thanks, FredR
 
#20 ·
i do not know the chemistry of the otc octane boosters, but my hunch is this is not true. We do not actively blend benzene, toluene, xylene (BTX as its called) into gasoline. But there are some levels of it in gas.

If this stuff is bonding to BTX in gas then those molecules are becoming heavier and therefore raising the octane level. However this would be raising it the wrong way, at least in my opinion. It is making a molecule that is already high compression stable and making it more so. But the light end things like natural gasoline (octanes in the 30-40 range) are still there to pre-ignite even though the toluene molecules are now heavier.

i have never considered the chemistry behind otc octane booster but i may look into it just to see how this stuff is suppose to work.

are you sure you really need 110+ octane. My knowledge here is a little more thin when dealing with the upper ends of CR, but i do know that running "extra" octane does not really add power (unless its HIGH enough to make the heat capacity higher and thus add more power potential).
 
#22 ·
i work at an auto parts store and one week i got bored and decided to see how much it really would cost to make a better grade of gas, and took the time to research it.... and i came to these conclusions. every single octane booster we sold was crap. most of them raise only a few points... and it takes 10 points to make one octane number. several chemicals from your hardware store help out... toluene and xylene probably being the best/easiest to find. however you cant get an effective mix if you go over 30% additive for previously mentioned low volatility. also, i dont know about your areas but toluene just so happens to be about 15 bucks a gallon.... so id just stick to airplane gas or getting it at the track...

small piston engine aircraft like cessnas run 100 low lead... and its really not that much over premium grade... some of you have paid the price for texas airplane gas in your states already for regular pump grade.. but thats if you have a tiny airport and its easy to get :wink:
 
#23 ·
Thanks again Cammer. I'm not sure if I need 110 octane or not, probably not quite that high but somebody here might! I was looking for the ratios to blend whatever octane I might need. I am planing to run about a 150 shot of NOS and was looking for a little added insurance. I have the engine built but haven't run it yet to find out.