Used oil in my gas tank?

Messages
1,502
Location
Indiana
Is there any downside to taking used motor oil, filtering it thru an oil filter, and adding to a gas engine, perhaps at 1qt per 20 gallons (80:1) ratio?
 
Messages
3,094
Location
Metro Detroit
I can see doing that to a diesel, but never a gas engine. I expect you would gunk up the motor, clog the cat and maybe ruin your O2 sensors.
 
Messages
2,698
Location
Silicon Valley
A four-stroke engine? You fogging for mosquitos? You ran out of fence posts to paint with used oil? Matt: you would let used engine oil go through the diesel fuel pump? Yikes!
 
Messages
3,094
Location
Metro Detroit
quote:
Originally posted by Tosh: A four-stroke engine? You fogging for mosquitos? You ran out of fence posts to paint with used oil? Matt: you would let used engine oil go through the diesel fuel pump? Yikes!
Do a search. There are threads about that on this board. I believe the consensus was that a small amount of used oil won't hurt it.
 
Messages
43,676
Location
'Stralia
I don't know why you'd want to do it, however, car manufacturers over there seem to think that 1 quart per 1000 miles is perfectly acceptable oil consumption. [Freak] So if you stick to 1 quart per 1000 miles as your total consumption (useage plus added), I doubt that you would be destroying anything. at 25MPG, that 1 quart to 40 gallons. I do not recommend this course of action, however.
 

blupupher

Site Donor 2021
Messages
7,063
Location
Katy, Republic of Texas
I guess the question should be "Is there any <i>upside</i> to taking used motor oil, filtering it thru an oil filter, and adding to a gas engine, perhaps at 1qt per 20 gallons (80:1) ratio?".
 
Messages
39,802
Location
Pottstown, PA
I've done this with my Rabbit Diesel ..but I don't know if it was "wise". I wouldn't be too worried about the engine...per se~ ..nor the emission controls/sensors. I'd be more worried about the fuel system (strainer/injectors) since you're introducing way more contaminants (or so I reason) than should normally be entering your tank.
 
Used motor oil is often highly acidic from combustion byproducts. You cannot filter out the acidity or other chemical contamination, only gross particles. I'd expect damage to fuel lines, injectors, etc., etc., over time after adding it to gasoline. I wouldn't even add it to diesel fuel.
 
Messages
661
Location
Bosphoria
My thinking is also with the 'manufacturers' normal oil consumption' theory. '25 Rover suggests that -if convenient- to add ½ liters of engine oil for the first tankfull of gas for easing the break-in period. However that is 1925! What benefit is aimed here? Better fuel lines, freeing up mechanical fuel pump? freeing up corrosion on the tank? Better cylinder lubricity? I wouldn't add used oil to tank at any cost though. May be some cheap fresh two stroke oil (for better mixing) at half the concentration at most. I experienced ¼ liter per tank (16 gals) which resulted in very slightly better revving (like would after an oil change).
 
Messages
47,950
Location
Everson WA - Pacific NW USA
Bad idea in a gasoline engine. Period. Just setting aside the pollution control part and the acidity of used oil part, oil is an octane reducer. If it's UCL you are after (and I believe there are some benifits) - I would look at some aftermarket additives, even ashless 2-stroke oil as mentioned, would be a better choice than used motor oil in your gasoline tank.
 
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