Central FL - Racetrak D2 with B5 to B20
Congratulations!
ou found one of the improvements of having D2 with B5 to B20 in it.
There are three questions that you brought up in your original post that need some expnsion on.
Fuel Filter replacement:
The fuel filter in the VW TDi line of Engines is designed to cause the water to preciptate and fall to the bottom of the canister, and either be returned to the fuel tank, or to stay in the bottom of the filter , and with a screw nut at the bottom, occaiisionally (once in 48,000 mi service).
Depending on the conistancy of the waxy particles(from the refinery-nlender), and their size, they may suspend in the fuel filter when cold, then when warm, the waxy crystals(clumps) would blend with the warmer fuel, and pass through the fuel system, enter the injectors, and get sprayed into the chamber and get burned with the cycle.
Improved MPG per tankful:
The improvement you found with the Bio blend, could be due to the blend of fuel, or the type of driving. (A 5% -10% variation can happen depending on driving style). The addition of the clean-lubricating bio oil is an addititive that perhaps improves the ignition timing to increase the burn time during the entire stroke.
Now that you have gone back to the regular Shell D2, do you normally add any Standyne or other additive that has 2-EHN (2-Exylhexylnitrate) as part of the formula?
In Canada, where I live, Shell offers a "Premium Diesel" fuel that has an additive (not available separate from the fuel) added at the pumps injected at a ratio of 2000:1 , (and a premium price as well).
There are some after-market fuel additives that have 2-EHN added as a significant part of their blend. I know if two that I have found contain 10 to 30% 2-EHN and when I add it to my fuel tank adds to my mpg performance.
Unfortunately, 2-EHN, is not available , nor is it advisable to mess with it since (from my reading of chemistry journals, that 2-EHN when in an un-diluted state is subject to be very volatile, and perhaps due to this volatility, is not so easily found.) it can be considered an explosive compound. (not sure at what quantity it is considered a hazardous substance).
It has been shown (see elsewhere use search) that 2-EHN does improve the fuel burn and the ignition timing is improved up to a blend ratio of 2000 ppm. After 2000 ppm (parts-per-million), the >2000 ppm blend was not able to improve the ignition improvement beyond what had already been achieved.
(just recently filled up after using an additive in the fuel mix, and the fuel consumed was 10 litres over 350 kilometers), [Yes , you read that correct , over 350 kilometers used only 10 litres of fuel] (This translates to 82.5 MPG!) (It was all highway miles, and I kept the throttle in cruise at 105 km/h, with a westerly tail wind.)
(now the fill up could be short by 5 litres, because I did not top-up, to maximum, (we had a heat wave, and I did not want to lose any due to temprature expansion that might have filled the car with 15 litres over 350 kms or 54.9 MPG)
Still not bad for a 16 year old car!
So see if there are any suppliers around that can supply the 2-EHN, and look for the B5-B20 blended fuel if available.
In Ontario, there is limited availability of B5, or at least the refineries do not advertise the blend(It actually costs more per litre than D2, and it is road taxed the same rate as D2(no break on taxes).
I hope this helps the discussion about fuel blends and additives.
Modifications to Fuel system:
There is no need for any modificationt to add B20 to your fuel tank, it is totlly compatible with your vehicle. With ULSD D2, the lubricity was reduced somewhat, with the reduction from 200ppm of Sulfur to 50ppm, however , the newer TDi engines were built with this in mind.
Some people add straight Canola to the tank, but this is not recommended, as the veggie oil has not been trans-estrified to remove the water, and make the oil compatible with D2. (I tried it in mine, it did not hurt, but my engine is a 2001 with ALH model code, I only added 10% STRAIGHT VEGGIE OIL (5 litres Canola per fillup).
Not mentioned - but noted elsewhere:
There are a few TDI drivers that plug in their block heater, to warm up the block before they drive off in the morning. It was suggested that by having the block warm, during the startup, there is less time, to bring the block up to running temperature.
Remember these are bassically heat engines that have a byproduct of rotationl energy, and one of the 'losses' in the search for better MPGs is the heat-up and cool-down cycle. (A smll one, but it is a noticable loss).
This was done even in Florida, where the ambient temperatures are not as extreme as further north. (Your Mileage may vary).