I once read about a chap who was using biodiesel instead of 2-stroke oil in the petrol of his chainsaw. Has anyone ever heard of using biodiesel as a 4-stroke petrol additive? I wonder if there'd be any benefits... Any thoughts?

G'day - I've been running my 2 stroke chainsaw on a 12:1 unleaded gasoline/bio mix for a few tank fulls now with no apparent ill effects - I'll report back periodically in response to requests to update any further outcomes.

I've read that a small addition of bio to 4 stroke fuel in a motor car situation can help with the obnoxious smells that modern gasoline vehicles put out.

I'm about to try this in my car which has the most vile smelling exhaust imaginable.

I suspect that this can only take place in a modern computer controlled engine management system that has knock detectors and will automatically retard the ignition timing to take inot account the poorer octans rating that adding bio to gasoline will result in.

The other effects of this action will be fouling of spark plugs, less power, smoke, fish & chips exhaust smell, gumming up of rings and valves etc etc all dependant on % bio used of course.

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Originally posted by Emporator:
I once read about a chap who was using biodiesel instead of 2-stroke oil in the petrol of his chainsaw. Has anyone ever heard of using biodiesel as a 4-stroke petrol additive? I wonder if there'd be any benefits... Any thoughts?

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Mixing veg based oils and petro based oils is not a good idea. Mineral oils tend to be polymerized by veg oils. Here's what happened to me:
Let me relate my story to you. My wife drives a 1998 Pontiac Montana minivan. 3.4L gasoline engine. I of course drive a Suburban TD. I make my Biodiesel from very lightly used soybean oil, and wash well. Last year my wifes van developed a misfire. After a short diagnostic procedure, I determined it to be a clogged fuel injector. (one must disassemble half of the engine to remove the fuel rail and injectors) The dealership has a method of hooking up a small pressurized vessel filled with injector cleaner and a small amount of gasoline. The fuse to the electric fuel pump is removed and this small tank is hooked to the fuel rail. The engine is then run until this small vessel is empty. Voila! Clean injectors. For the nominal fee of 250 dollars! Now I am aware of Biodiesels excellent solvent capabilities, so I wondered if it would do a good job of cleaning the injectors. I filled the tank with a 10% blend of BD and gasoline. Within 50 miles, the mis-fire went away and the service engine soon light went out. I ran two tankfuls of this 10% blend in the van. I thought WOW this is great! I can cut her gasoline usage and keep everything clean and running great as well. My balloon was quickly deflated soon after these two tankfuls. The soy bean derived BD polymerised the engine oil. A couple of close spaced oil changes cured that, but I have not experimented again with BD in an SI engine. Now I realize there are several factors that could be the culprit. Mineral oil in the van (I use Mobil 1 synthetic in my 'Burb), A fouled injector causes fuel dilution of the crankcase oil (perhaps a good running engine would not have experienced the polymerization), or maybe BD made from a different plant oil would not cause the polymerization. I don't know, I have not carried out further experiments on it. The van ran very well on the 10% blend BTW. Just a heads up about something to be aware of with veg oil or BD in an SI engine.(the polymerization). end post.

So, the mineral oil in the enigine polymerized within two tankfuls of a 10% blend. It did do a marvelous job of cleaning the fouled injector. Yes, this gasser is fuel injected not carbureted. Perhaps synthetic oil would not have polymerized.
This is a copy of a post I made earlier. HTH

Joe,
Please post a link to that thread, so that others can read the replies you recieved.

IIRC, there were comments along the lines of:
* Biodiesel does not burn completely in a SI engine. This will cause some partially combusted biodiesel to dilute the engine oil.
* Petrol which dilutes the crankcase oil evaporates relatively quickly.
* Biodiesel in the crankcase however does not evaporate. It has been partially burned (exposed to combustion temperatures). It is in a high temperature environment with intimate contact with air.
* 2 tanks in your minivan (edited 9th Jan 05) would have been about 800 miles. Assuming that your speed was 50 mph, this is 16 hours of the biodiesel being kept at ~90'C and sprayed/splashed into the air within the crankcase.
No wonder it polymerised.

My new comment:- If you wish to use biodiesel as an injector cleaner, please only use a small amount (preferrably using a temporary fuel tank) and change the engine oil after the biodiesel has been totally consumed.
Tony

This message has been edited. Last edited by: Tony from West Oz (The Wizard of Oz),

Tony,
Here is the link.
There seems to be a slight misunderstanding. My Suburban is a turbodiesel, my wifes minivan is a gaoline engine. It has injectors as well. Port fuel injection on gasoline engines is how almost all newer engines control mixture. The GASOLINE injectors got dirty and BD cleaned them quickly, but polymerized the crankcase oil. My Suburbans oil never became polymerized. Synthetic in the 'burb (Mobil 1 15W 50) mineral oil in the Montana.

VERY INTERESTING...I just saw some "ring and land carbon cleaner" in the marine store. I read the instructions and it said you MUST CHANGE the oil right after the cleaning if you use it at the higher "cleaning" concentration.

Yeah I used vegie oil as bar lube on the chain saw and was disappointed to fine it developing gluggy lumps which could have fouled the bar lube feed mechanism.

Dana did tell me once he tried using vegie oil in petrol for 2 stroke but needed so much of it in the mix as to foul the plug in a lawn mower. i haven't tried BioD in a 2 stroke mix... too expensive in Aus and we aren't allowed to make it.