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-   -   biodiesel as fuel additive for gasoline (https://www.fuelly.com/forums/f20/biodiesel-as-fuel-additive-for-gasoline-3869.html)

GasSavers_nathan 02-11-2007 05:59 AM

biodiesel as fuel additive for gasoline
Anyone run biodiesel as a fuel additive in a gasoline vehicle?
I'm going to try it but wanted to know if theres anyone who's experimented with it already.
i was thinking id start with 250ml for a 40l tank, then increase until i find the ideal amount. Does anyone know what type of damage i could cause by putting too much in? Im expecting i'll need to change my fuel filter after i start using it.
I track my FE but because i have a carburetor theres no way to accuratley measure it. the best im able to do is run my tank down near empty and fill up again. i wish there was a scanguage device for carb'd cars.
i'll have to wait till my next tank to add it because this tank im testing a front air dam. should be later this month.

MetroMPG 02-11-2007 06:41 AM

Check here:


GasSavers_nathan 02-11-2007 07:33 AM

ah sweet. thanks metrompg. i knew i remembered reading something about that before. guess i should have searched a bit.

Lug_Nut 02-11-2007 05:20 PM

There are other, better tested, 'top cylinder lubrication' fluids than biodiesel. Have you considered ashless two stroke oil as an additive? Biodiesel is almost non-flammable due to its high flash point and low volatility. I'd be concerned about running it in a spark ignited engine.
Typical diesel engine rpm maximum is 3500 to 4500. That is the limit created by the time needed to vaporize and burn the fuel (diesel or biodiesel). The engine can't run faster because the burn and expansion rate isn't faster. At those speeds the piston is being pulled down by the connecting rod as much as it is being pushed down by the combustion expansion on top.
Adding diesel or biodiesel to gasoline and then running the engine rpm above these levels may lead to not enough time for the diesel fuel portion to burn. The gasoline will be consumed but there may be some continued burn of the small proportion of fuel oils during the upstroke for exhaust.
I tried to 'use up' some bottom of the barrel biodiesel in a flathead lawnmower engine at a 20% rate to unleaded gasoline. Twenty percent wasn't a help. I don't expect that 10% would have been anything but 1/2 as un-helpful as 20% was. The exhaust smelled better than gasoline, but it didn't run as well. Would fresh biodiesel have had different results? Maybe, but why would I put good quality expensive biodiesel into a non-diesel engine?
I now have a diesel lawn tractor to use up the biodiesel dregs (and kerosene, and home heating oil, and neighbors turkey fryer oil, etcetera) that I won't ever put in my diesel car.

GasSavers_nathan 02-11-2007 07:20 PM

if you're driving for FE then i wouldn't think your rpm would be higher then that anyway. and although bioD may not be the best top cylinder lube it should be better then nothing. plus the cleaning effect could be beneficial on an old carb.
I've made a small one liter test batch already using the dr pepper technique so i'll dump it in with my next tank.

zpiloto 02-11-2007 07:47 PM

What are you trying to accomplish with BioDiesel? If it's to clean the fuel system just run some acetone and Torco GP7 for a few tanks or even a mixture of 20%-30% E85. I've had a slight increase in FE running a mixture of E15.

Diesel has octane numbers around 15-25. They tend to ignite easily from high compression.

Diesel fuel is rated by its cetane number. Instead of heptane and iso-octane they use napthalene (cetane rating = 0) and n-cetane (cetane rating = 100). In total opposite to octane ratings, the higher the cetane rating the higher the fuel's propensity to knock! Adding biodiesel to regular gas is liable to drop the octane rating that you currently have and thus decrease FE because the engine is designed for a specific octane rating.

Lug_Nut 02-12-2007 06:28 AM


Originally Posted by zpiloto (Post 40498)
They tend to ignite easily from high compression.

How high is 'high'?
Don't minimize the importance of fine atomization possible from pushing fuel at 30,000 psi through .184 mm nozzles. A 60psi fuel injector for gasoline won't break the drops of fuel into a near vapor size needed to compression ignite. A carburetor venturi definitely won't. The drips of biodiesel will burn when lit by the gasoline, but not too well on their own.
Sawdust and a tree trunk are the same substance, but one ignites more easily than the other. Biodiesel liquid at 60 psi and 8:1 compression is more like a log than biodiesel atomized by 30,000 psi and 20:1 compression.

GasSavers_Ryland 02-12-2007 12:27 PM

I only put around 200 miles on my Honda CB125 motorcyle with a 10:1 mix of bio-diesel in it befor putting it away for the winter, but I never had a problem with how it ran, I even put an o2 sensor in it to make sure that it wasn't going to foul up o2 sensors, and as far as I can tell it's not causeing any problems.
I didn't notice any jumps or drops in gas mileage with bio-diesel, it seemed to burn just like gasoline when mixed at 10:1, sure one part bio-diesel to ten parts gasoline is not alot, but it's as high of a mix as I could get without making any adjustments to the engine, I also found that my motorcycle was able to keep the exact same top speed (almost exactly 60mph), and the o2 sensor readings seem to stay pretty close to the same with the mixed, and unmixed fuels.

so I say go for it, from what I've been able to tell, it's not going to harm anything, altho I haven't seen any magical results either.

GasSavers_nathan 02-13-2007 10:41 AM


Originally Posted by zpiloto (Post 40498)
What are you trying to accomplish with BioDiesel?

mainly i just want to see what it does as a fuel additive.


Originally Posted by zpiloto (Post 40498)
Adding biodiesel to regular gas is liable to drop the octane rating that you currently have and thus decrease FE because the engine is designed for a specific octane rating.

on a car with a fuel injection and a knock sensor i could see a lower octane rating hurting FE but because i have a carb i don't think it would hurt my FE unless the octane rating dropped enough to cause pinging.

JanGeo 02-13-2007 11:06 AM

Back in the Rambler days I ran a little home heating oil in the gas - well I don't recommend using it in a Fuel Injected car. In a carburated engine it made a lot of white smoke when cold and kept running with the ignition off when the concentration was a little too high after it warmed up. Now with the Synlube in the engine I don't have to worry about top cylinder lube but I do have to worry about any additional lubricant getting into the Synlube and fouling it up.

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