Bio-diesel in Jetta Sportwagen

I recently bought a used Jetta Sportwagen 2011 in very good condition. I would like to start using biodiesel in it but both mechanics I’ve talked to have said that over time it will ruin my engine due to undependable quality of the biodiesel fuel out there. The distributors of the fuel in my area claim it is completely fine and I should have no problems.
Who should I believe? The dealer recommends no more than 5% biodiesel mix for this car but am wondering if I could get away with 20%.

Not if you want it to work. Only use the % biodiesel allowed by VW. Typically 5%. Check your owners manual.

And check the source of that biodiesel. Some comes from palm oil grown on plantations created by razing rain forests.

+1 for @texases. Check your owner’s manual and stay within their guidelines. Cheaping out on fuel could ruin your engine.

Check your owners manual.
Check your owner's manual and stay within their guidelines.

Owners manual? You’re kidding right? Aren’t owners manuals just an urban myth? (sarcasm intended)

I think you should go ask this question on a forum where people own & discuss VW diesels.

Could that forum be

I would not rely on any advice that contradicts the owners manual on this. Biodiesel folks can be, let’s say, “over enthusiastic” when it comes to %.

There appears to be no advantage for VW to push biodiesel, and although they may be conservative with their 5% number, there is no good reason for you to use more and that may have something to do with VW’s number.

Biodiesel is expensive; my last 5 gallon buy last autumn cost over 8 dollars per gallon, presently about twice the cost of petroleum diesel. My guess is that the same arguments about corn ethanol’s effect on food cost apply to biodiesel. 5% biodiesel does an excellent job of ensuring adequate lubrication for your injection pump if the fuel vendor falls short of adding the necessary lubrication additive to ULSD which is why I use it, one quart per tank fill, usually about 12 gallons.

Here is a post found on that you may find interesting as I did as I still run an old IDI VW diesel.

Injection pump pressure in a TDI diesel is approx. twice that of an IDI diesel so 5%biodiesel might be good for your TDI diesel.

What does your owner’s manual say?

Do NOT use 20% biodiesel

You will most likely regret it

Various parts of your fuel system will eventually suffer damage. Maybe not right away, but the damage will occur over time

Do NOT do anything that contradicts VW’s advice

To tell you the truth my nieces husband, an engineer at some expensive jet company, gulfstream I think, did a cross country trip using restaurant oils while in college in a vw diesel.


An acquaintance had a fairly expensive kit installed in his Benz diesel car some years back, so that he could run it on vegetable oil

It was a high quality kit installed by a reputable company. And this guy only used new vegetable oil. Nevertheless, the stuff eventually did a number on his fuel system. He finally gave up on the car, because the fuel system just wasn’t reliable anymore.

All I know is they made the trip from Atlanta to CA and back.