BioFuel Oasis

Biodiesel FAQs

What is Our Petroleum-Free Fuel?

Will this fuel void my warranty?

What is Biodiesel?

Benefits of Biodiesel

Cautions of Using Biodiesel

Running Biodiesel in 1999-2006 Volkswagen TDIs

Legal Status in California

Finding a Diesel Car

How a Diesel Engine Works

How to Make Your Car Last a Long Time

What If I Need to Buy Petrodiesel When I Can’t Get Biodiesel?

What If I’m Not Going to Drive My Car for Months?

What is Our Petroluem-Free Fuel? [back to top]
Our Berkeley pumps continue to be petroleum-free with this blend:

  • 20% Local, Recycled, Biodiesel – Made by Simple Fuels in Chilcoot, CA from recycled vegetable oil
  • 80% Renewable Diesel – Currently made by Renewable Energy Group (REG) in Louisiana, USA from recycled vegetable oil and tallow.

The renewable diesel is significantly better than petroleum diesel & is made from the same recycled vegetable oil sources as biodiesel. We are happy that we have the option of continuing to avoid petroleum.

Will this fuel void my warranty?[back to top]
Renewable diesel looks like the petro diesel molecule and meets all manufacturer warranties for petro diesel. Most vehicle manufacturers now warranty of B20 (20% biodiesel), so our fuel blend does not void most warranties.

These manufacturers support B20(20% biodiesel):
Ram, Jeep, Cummins, Ford, GMC, Chevy, Isuzu

Audi and Volkswagen allow up to 20% biodiesel in Illinois and Minnesota and are actively researching the B20 blend. The blend is unlikely to harm the engines since they have been forced to allow it in those two states.

For a complete list, click here.

What is Biodiesel? [back to top]

  • Biodiesel is oil that has been modified in a chemical process called transesterification in which the glycerine is removed from the oil. The resulting product is thinner than vegetable oil and can power a diesel engine as a fuel with NO modifications or conversion needed. It can also be blended with petroleum diesel in any proportions, right in your tank. If you can’t find biodiesel you can still use petroleum diesel. Details about how biodiesel is made and the equipment to do it can be found here:
  • Straight Vegetable Oil is not the same as Biodiesel. When people talk about converting a diesel they are usually talking about the modifications needed to run it off of straight vegetable oil (SVO) or waste vegetable oil (WVO). In an SVO system, the oil is thinned by heating the fuel tank and/or fuel lines before it is sent to the fuel injectors. SVO systems have not been in use for as long as biodiesel and are still somewhat experimental. See these sites for more information: or
  • Biodiesel blends: You may have noticed biodiesel labeled as B5, B20, B50 etc. The number next to the “B” indicates the percentage of biodiesel found at that particular location. B5 means the fuel is 95% petroleum diesel with only 5% biodiesel blended in; B20 is 80% petroleum diesel with 20% biodiesel. At Biofuel Oasis we specialize in selling B99.9 the highest biodiesel blend commercially available (99.9% biodiesel, .1% petroleum diesel). Our customers have experienced confusion by stations just using the word “biodiesel” when they are selling low blends like B5 (95% petro, 5% biodiesel). Be sure to ask what percentage biodiesel it is before filling your tank, so you can make an informed decision. The BioFuel Oasis is the only station in the East Bay selling a blend higher than B5.
  • Sustainable Biodiesel: Not all Biodiesel is created equal. BioFuel Oasis is committed to selling and sourcing biodiesel made from recycled vegetable oil. Biodiesel made from virgin agricultural oils can displace food crops, can exacerbate the social and environmental problems of industrial agriculture and can have a large carbon footprint because it is often shipped from overseas. We prioritize sourcing biodiesel made within a 200 mile radius of Berkeley.

Benefits of Biodiesel [back to top]

  • Easy – no conversion to your vehicle and biodiesel can be splashblended with diesel at any time in your fuel tank.
  • Non-Toxic – biodiesel is the only alternative fuel to have completed the EPA Tier I and II health testing. The test results concluded that biodiesel is non-toxic and biodegradable, posing no threat to human health.
  • NonFlammable – biodiesel will only ignite at a very high temperature (350° F). As a comparison, gasoline ignites at -43° F.
  • Good for Your Engine – tests show that biodiesel is more lubricating to both your fuel injection pump and engine than diesel fuel and so may prolong your engine life.
  • Renewable – biodiesel is made from 85% vegetable oil, a renewable resource.
  • Cleaner Emissions – greenhouse gases, particulates, and carcinogens are greatly reduced.
  • Sustainable – in a cradle to grave life cycle analysis, biodiesel comes out positively. For example, one study showed that biodiesel yields 3.2 units of fuel product energy for every 1 unit of fossil energy consumed in its life cycle. By contrast, 1.2 units of fossil resources are used to make 1 unit of diesel fuel.

Cautions of Using Biodiesel in Your Vehicle [back to top]

  • Paint – Over time, biodiesel may dissolve the paint on your vehicle. Wipe off immediately or wash with a little soap and water to prevent this from happening. At our pumps at the BioFuel Oasis, we have red rags and bottles of nontoxic degreaser for you to use.
  • Rubber Hoses and Seals – Most pre-1994 vehicles and some later model cars (all Mercedes) have non-biodiesel compatible fuel lines. Gradually, over 6 months to a year, biodiesel will degrade these fuel lines, which will become malleable, weepy or spongy before they completely melt. Check under your hood periodically and replace any degraded fuel lines and seals with a biodiesel resistant synthetic, such as Viton or A1 grade Marine fuel line. The BioFuel Oasis sells viton fuel lines that are biodiesel resistant.
  • Fuel Filter Clogging – Biodiesel is a great solvent which will clean out your entire fuel system. Your vehicle may have a lot of sludge in your fuel tank/system built up over the years from running diesel fuel. Biodiesel will dissolve the diesel residue; if there’s enough, it may clog your fuel filter. The symptom of fuel filter clogging is a power loss; you put your foot on the accelerator pedal, and the vehicle responds very slowly or will only go up to 30 m.p.h. on the freeway. If your car has been running on petroleum diesel for many years, we recommend changing your fuel filter 2 months after switching to biodiesel. This should catch the filter clogging early enough before you have power loss. Keep an extra fuel filter in your vehicle, learn how to change it, and be prepared. The BioFuel Oasis offers filter changing workshops. Detailed instructions on changing the filter in a VW TDI are posted on Fred’s TDI Club FAQ page.
  • Cold Weather – Biodiesel gels/crystallizes at around 32°F or higher depending on what kind of oil/fats it was made from. Petroleum diesel fuel gels at around 10°F. As fuel gels it becomes thicker, clogs your fuel filter, and can cause power loss problems. Fuel stored in carboys will form white deposits at the bottom. If it gets cold enough your whole tank or carboy will just be white frozen biodiesel. If biodiesel freezes in your fuel lines and injection pump your car will not start. This won’t cause damage; you just need to warm up your vehicle (usually means getting it towed somewhere).

    • Blend in some petroleum diesel to lower the gel point. The exact percentage needed to prevent gelling will vary depending on they type of vehicle, the feedstock of the fuel, and weather conditions. In the SF Bay Area a blend of 20% diesel should be enough to get you through a cold spell. If you plan to go someplace colder like Tahoe run at least 50% diesel, or just run diesel to be safe.
    • Store extra fuel containers in a warm location.
    • Heat or insulate outdoor storage tanks.
    • Some cars (usually trucks) come equipped with engine block heaters that can be plugged in overnight to help the car start on cold mornings. If you don’t have an engine block heater you can put an incandescent work light under the hood at night to keep the engine compartment warm.
    • Park indoors if indoor parking is available, if not, park where sun will hit your car early in the morning.
    • People who live in colder climates can add heating elements and insulation to the fuel system to prevent gelling.

    • When fuel gels it needs to be brought well above the gel point temperature – probably 70 degrees or higher – to return to a stable liquid state.
    • The passenger compartment of a car parked in the sun can get warm enough to melt any gel in your carboys.
    • Put a carboy or a mason jar full of biodiesel outside and look at it in the morning to get an idea of what’s going on in your fuel tank. If there’s a white layer on the bottom, you can expect problems.
    • Change your fuel filter if you are experiencing power loss. Filing up with diesel can help if your fuel filter is clogged and a replacement is not handy. Diesel is thinner than biodiesel and will get through a partially clogged filter better than biodiesel.
    • Park your car in the sun and wait till the afternoon when it’s warmed up until driving.
    • Aim a blowdryer at the fuel filter and fuel lines.
    • Pour hot water over the filters and fuel lines. Do this carefully, avoiding electrical components.
  • Uninformed Mechanics – Mechanics who are unfamiliar with biodiesel may misdiagnose unrelated problems as being caused by biodiesel and perform unnecessary fuel system purges or other expensive “repairs”. We recommend locating a biodiesel-friendly mechanic in your area before you need one. Dealers are particularly notorious for “diagnosis by bumper sticker”. Get a second opinion from an informed mechanic (VW) before allowing expensive work to be performed. Lastly, please call us when a mechanic blames a problem on biodiesel. We are happy to call the mechanic. This is especially beneficial before you’ve had work done, as we can save you unnecessary repair.

Running Biodiesel in 1999-2006 Volkswagen TDIs[back to top]

General Recommendation: Half our customers have VW TDIs and they run well on 100% biodiesel. Avoid running 100% petroleum diesel in the VW TDI. Keep at least 25-30% biodiesel in them when you go on trips and biodiesel is difficult to find.
Why? When California switched all petroleum diesel to Ultra Low Sulfur Diesel (ULSD) in October 2006, we had customers report seal leaks in the fuel injection pumps. It particularly happened in the summer of 2007, when our customers went on road trips and put petroleum diesel in their tanks because they couldn’t find biodiesel. We surveyed our customers that had their fuel injections pump replaced and found that they only had the problem after putting petroleum diesel in their car. We also discovered many customers that put biodiesel back in their car and it fixed the problems.
How could petroleum diesel (ULSD) cause fuel injection pump failure?
Injector pump seals: The pre-October 2006 formulation of petroleum diesel caused pump seals to swell, and biodiesel swells seals even more. ULSD causes the seals to shrink and harden. Too many changes can damage the seals and the pump will leak fuel and/or suck in air. Most of the failures due to damaged seals have occurred in cars that have run on all three types of fuel. Three fuel changes may simply be too many. Injector pump seals that are only exposed to two types of fuel, biodiesel and ULSD, seem to be fine.
Which cars are affected the most?
In our survey of customers, we found that 2000-2003 VW TDIs were the ones usually affected. We also have not had anyone report a Jetta Wagon with this problem. Jetta Wagons were made by a specific factory (in Germany) and may have injector pump seals that are impervious to the problem.
Is it possible to avoid this problem when looking to buy a used VW TDI?
Look for a VW TDI that had the fuel injection pump replaced since October 2006. It’s likely that the pump seals will be fine switching between biodiesel and petroleum diesel. You still may want to be cautious and avoid abrupt switches from 100% biodiesel to 100% petrodiesel. Buying a Jetta Wagon will also likely have no problems (see above).
How can I take a long road trip where biodiesel might not be available?
It’s definitely possible, especially if you take a couple 5 gallon carboys of biodiesel with you. The goal is to keep at least 25% biodiesel in your tank at all times. Here’s how you do it. Fill up your tank with 100% biodiesel plus two 5 gal carboys. When your tank’s ¼ full, fill up with petrodiesel. When you get down to ¼ tank again, pour in one carboy and top off with petrodiesel. Get down to a ¼ tank one last time, pour in one carboy and top off with petrodiesel. This should get you 1800 miles at 42 mpg or 2150 miles at 50 mpg. You can also look click here to find other B100 biodiesel stations around the country.
What is the symptom of my fuel injection pump seals leaking?
The most common symptom is that you can’t start your car, because the fuel has leaked out of the pump overnight and so there is air in your fuel lines. Look under your car and see if there is a puddle of fuel.
If your injector pump does fail!
  • First, try switching back to biodiesel. Several people have reported that running at least 30% biodiesel re-swells the injector pump seals and stops the leaking. Let the injector pump absorb the biodiesel for 24 hours or more before giving up.
  • If you can’t get biodiesel, try a diesel fuel additive. Customers have reported that Red Line Diesel Fuel Catalyst additive has swelled their seals and mostly stopped the leakage, until they could get biodiesel.
  • Avoid the dealer unless you can get the repair done under warranty. VW dealers typically charge $3k to replace your injector pump and fuel injectors and purge your entire fuel system. The same repair done at an independent garage typically costs half or less of what VW charges. Dealers are also notorious for diagnosing all fuel system problems in cars with biodiesel stickers as injector pump failures, and have recommended $3k repairs when they simply failed to bleed the air out of a new fuel filter.
  • If something doesn’t feel right always call us at the BioFuel Oasis or get a second opinion before agreeing to an expensive repair.
Where to go for Injector Pump Rebuild:
These business only rebuild pumps and do not work on cars. Have your pump removed and send it to:
  • Diesel Fuel Injection Service, 8922 NE Vancouver Way. Portland, OR 97211. (503) 235-1947.
  • Diamond Diesel, 2550 East 12th Street, Oakland, CA 94601, (510) 532-8500AND
  • Use Viton seals: Viton TDI injector pump o ring seals are available from They also sell the basic Bosh rebuild kit if you want to do the repair yourself.

Legal Status in California [back to top]

Biodiesel: The first time you purchase fuel from us you’ll be asked to sign a service agreement and provide information on the make and model of your car. We’ll also request your contact information and that you inform us if you suspect a mechanical problem caused by biodiesel. Here’s why:

On August 19, 2004, the CA Division of Measurement Standards bowed to the pressure from the petroleum industry and prohibited the sale of fuel containing more than 20% biodiesel to the public. The ASTM standard for biodiesel is titled “ASTM D6751 – Specification for Biodiesel Fuel Blend Stock,” meaning that it is to be used in some blend with diesel #2. The “blend” language in the standard forces DMS was to regulate the sale of B100 and high percentage blends as non-standardized fuel.

Yokayo Biofuels, Biofuel Station, and BioFuel Oasis have been granted a waiver by DMS that allows us to sell B100 as a fuel on the condition that we file quarterly reports on the vehicle types, amount of fuel used, and any fuel-related problems. We assign each customer a number for use in reports to the state. No personal information is included. You will receive a card with your number that will need to be shown in order to purchase fuel.

Cards from the stations that were granted this variance are valid at the following locations:
Real Goods Solar Living Center – Hopland, CA
Yokayo Biofuels – Ukiah, CA

The Biofuel Station – Laytonville, CA
BioFuel Oasis – Berkeley, CA

Diesel Autos: Beginning in 2004, the California Air Resources Board required that new diesel automobiles (not trucks) have to pass California smog regulations to be sold in the state. This was not possible with the sulfured diesel fuel that was sold in CA until October 2006.

You can purchase a used diesel automobile that was previously registered in California . You can only purchase a diesel auto from another state and import it into California if it is used with at least 7500 miles on it at the time of purchase.

Now with only Ultra Low Sulfur Diesel being sold in California it is theoretically possible to install emissions control devices that will allow diesel autos to pass smog. New diesel autos with those emission control devices have not yet been made available. Until that changes the 2004 rules still apply.

Finding a Diesel Car [back to top]

    Look everywhere:,, A couple of independent California auto dealers specialize in recent model VW diesels: Diesel Depot in San Rafael, and Ahl Motors in Ukiah. Some California VW and Mercedes dealers have figured out that there is a strong market for diesels and get them in used whenever they can. And dealers near the border in Oregon and Nevada also keep a lookout for slightly used diesels to sell to Californians.
    Remember, there are special recommendations for using biodiesel in a 2007.5 – 2012 vehicle

Finding Biodiesel on the Road [back to top]

    If you’re planning a road-trip out of town or state, check out these Biodiesel Locater Maps found online:
    Be sure to call ahead for current store hours and up to date fuel information. It’s not uncommon for stations to change the biodiesel blend at the pump, or to have different hours of operation than stated on biodiesel maps.

About Diesels [back to top]

Rudolf Diesel invented the diesel engine in the 1890’s to be more efficient than the steam engine. It is still the most efficient internal combustion engine today. Diesel cars and trucks get much better mileage than their gasoline counterparts; the small diesel compact cars normally get 40-50mpg!

In diesel engines the air is compressed up to a 25:1 rate. When air is compressed, the temperature goes up. In diesel engines, the temperature is raised to up to 1500 degrees Farenheit. The fuel is ignited by the extremely high temperature and no spark is needed like in a gasoline engine. Nonflammable materials like vegetable oil and biodiesel can be used to fuel a diesel engine because of the high temperatures and pressures achieved.

How a Diesel Engine Works

The diesel engine has four strokes similar to the gasoline engine:

  • First Stroke – INTAKEThe piston moves down and sucks in air.
  • Second Stroke – COMPRESSIONThe piston moves up and compresses the air up to 25 times its original volume. The temperature rises up to 1500 degrees Farenheit.
  • Third Stroke – IGNITIONFuel is sprayed in and ignites from the high temperature. The explosion drives down the piston.
  • Fourth Stroke – EXHAUSTThe piston moves up and pushes out the burnt gases to your exhaust system.

Differences Between a Gasoline & Diesel Engine


  • A gasoline engine intakes a mixture of gas and air, compresses it and ignites the mixture with a spark. A diesel engine takes in just air, compresses it and then injects fuel into the compressed air. The heat of the compressed air lights the fuel spontaneously.
  • A gasoline engine compresses at a ratio of 8:1 to 12:1, while a diesel engine compresses at a ratio of 14:1 to as high as 25:1. The higher compression ratio of the diesel engine leads to better efficiency.
  • Gasoline engines generally use either carburetion , in which the air and fuel is mixed long before the air enters the cylinder, or port fuel injection , in which the fuel is injected just prior to the intake stroke (outside the cylinder). Diesel engines use direct fuel injection — the diesel fuel is injected directly into the cylinder.

How to Make Your Car Last a Long Time [back to top]

It’s better for the environment to take care of your car and have it last a long time. The more people that do this, the less new cars will be made.

  • Don’t use your car mostly for short trips. Car engines are made to get up to temperature and running there for at least 10 minutes; this means driving at highway speeds for 15 or more minutes. An engine running for months only on short trips won’t last as long. Save your car for freeway/highway driving. For short trips, ride your bike, walk, and take public transit instead.
  • Change your engine oil every 5000 miles. This will make your engine last a long time. Be sure to use the correct oil and use fully synthetic oil. For Volkswagen TDIs, the oil needs to have a CG-4 or CH-4 rating. Click here for a detailed explanation and list of oils at TDI Club.
  • Check your oil dipstick every time you fill up with fuel to make sure your oil level isn’t low. Also check for any fuel leakages (biodiesel can eat rubber coolant hoses), coolant, or oil leaks, and take care of them immediately. Be proactive about finding leaks and other things before they get serious and damage other components.

What If I Need to Buy Petrodiesel When I Can’t Get Biodiesel? [back to top]

Buy petrodiesel from a truck stop that sells lots of diesel (rather than a gas station that sells very little). The quality is better at a truck stop, because commercial truck buys hundreds of gallons of diesel at a time, and will sue a truck stop for bad quality fuel and warn other truckers.

What If I’m Not Going to Drive My Car for Months? [back to top]

If you are going to leave your car for a few months without driving it, put in petro diesel and add additives to the tank: biocides to prevent microbial growth and stability additives to slow the fuel from breaking down/oxidizing. Also, consider loaning your car to a friend so they drive it regularly (and can keep it on biodiesel).

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