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Discussion Starter · #1 ·
It seems as though the Biodiesel discussion is nearly dead with fuel prices being low(er) again, but I thought I would contribute a "guide" to running biodiesel in a Duramax for those that may still be interested.

A little background first. I have been making homebrew biodiesel for 13 years. I ran a 12V cummins (and many other machines) on my fuel for 185,000mi. Sold the cummins to buy a crewcab dmax (needed room for the kids). Never had a fuel related failure of any kind. Sold the cummins at 340,000mi and it ran like a top. Not trying to toot my own horn, but I know my way around diesels and making good biodiesel.

This thread focus is on QUALITY biodiesel, not SVO, not WMO, not WVO.
There are many ways/means to ensure quality fuel, but this thread is not the focus of that.
I have been running B100 (other than winter blending needs) for the last year in my LLY.
The hoses and fuel system CAN handle B100. The only issue I have come across is the filter head leaking. The filter head is a problem with straight #2D so its not surprising that bio makes it worse. I have a ordered a Viton seal kit to install, but the cup seals on the plunger appear to be regular rubber. If it leaks again I will install a machined head from Nictane and be done with it. No other fuel leaks noticed.
I recommend a lift pump. Bio is a little thicker and pushing it to the cp3 will only help. Lift pump is good anyways. I would caution against the lift pumps with filters directly mounted to them that mount under the truck. They will get full of ice and snow and biodiesel will not flow through when its cold. I put just a lift pump mounted near the tank and do the filtering with a CAT 2 micron filter in the stock location. You want the heat from the engine bay. I also installed a silicone heated wrap around the filter that is powered from the factory fuel heater lead (relayed and fused independently). This setup works well. I cant run B100 all year long, but it does help on the cold mornings when you have a little too much bio in the tank and still have to get to work. Fuel filtration is critical. Good and/or better practices than regular diesel should be done. Changing often, 2 micron filters, etc.
I recommend a good additive to use in your fuel. Not for a cetane or lubricity boost. Don't need that with biodiesel. You want to help control oxidation, water and injector deposits. I use Primrose 2030. Very good additive in my opinion. I make a lot of fuel at once and store it over months, the additive is added to my tanks when I store the fuel.
I have noticed ZERO problems with lube oil dilution and in fact the oil stays clean for about 4000mi after an oil change. Its crazy how long it stays clean.
I think these engines would need all the above plus a delete in order to run B100. Post injection will not work with B100. LML might be able to do it with the 9th injector, but many are still under warranty and I have not seen anyone report that it does work. If I could afford a LML I would run the experiment just to see.
Good luck and happy smooth, quiet motoring!

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Own a 2007.5 duramax. Think that makes it the LML. Been running b100 for over a year. Have a little tuner on it because we did the delete and you gotta program out the cel.

So...FYI The truck dropped the cp3 last year. Check valve inside the fuel filter housing failed and stuck closed starving the Ip and cooked it. 3800 bucks. I was traveling with my 5th wheel 400 miles from home...no options.
Have the fass lift pump and that couldn't overcome the blockage. Live in southern climate so ice and freezing not a big concern.

The guy did a "field delete" of stock fuel filter by just ripping the guts out and reinstalling the filter can as the fass has better filtration. When he found that little ball valve and spring serving as a cheap check valve inside filter housing it explained everything. He just ripped it out. Don't need it.

Guy said it wasn't fuel related but who knows. Beyond that...I don't mind b100 when I'm tooling around empty but when I hook to weight I blend 50/50 therabouts. Too much loss in power and my fuel mileage drops. 50/50 is awesome though. And b100 perfect for day to day. Still running b100 otherwise unphased.

Runs quieter and smoother on b100/b50 than Dino.

My vw gets b100 year round.

I use a biopro I bought used and cheap. But...i still titrate every batch etc. and manually process. the biopro just does the washes and drying cycle for me automatically...which is freaking awesome. I can turn 50 gallons in about 36 hours finish dried and pumping to storage. I centrifuge directly into processor.

I also 5% hot prewash which is in my humble opinion...the best step of making bio. I can turbulent wash from go which cleans so much better. We all have our own little bd hacks. Some guys don't care for the prewash. Works for me as I go a touch heavy on catalyst to avoid having to re-react. (I hate failed or incomplete reactions. Haven't had but a couple when I was early on trying to dial in my recipe.)

Anyway. Know the thread is old. Just thought I'd throw in on that. If you have a lift pump you may want to remove that cheap a$$ check valve inside the filter housing. It's only purpose is to keep fuel from draining out when you change stock filter. With lift pump you can pump it right back up no worries.

Reach back out would love to hear how you process and any duramax thoughts you have

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