Hypothetically speaking, would it be possible to devise a simple home test for the presence of rape methyl esthers ie biodiesel in a sample of engine oil? Maybe some kind of test for organic compounds? But I suppose mineral engine oil is still organic ultimately.

I know people do analysis mail order and what not, just wondering about the above question.

I severely doubt it. Just how many people do you know that have a GC-MS in their living room?

Organic in this instance means that it is made primarily of carbon and it is likely that synthetic oils would also be organic. There would be ways of detecting different oils but these are likely to be some sort of chromatography or possibly distillation. It's is very unlikely that a household would have suitable equipment.

Out of curiosity, why would you want to know?

Interesting…

If you know there are no other esters, I guess you could do an ester test (will dig out the simple method if you want), but tbh, without a reference standard and a GC/HPLC I doubt yourever going to know what you have in there to any degree of certaincy, even then as mentioned your going to need a MS (and to be 100% sure a NMR).

Tempted to do some tests, maybe chromatography or rig up a centrifuge or something, see what happens 🙂

Fairly easy in a lab: GCMS and/or NMR against reference samples will show it up but kitchen chemistry – don't think so.

i would whack it in my mass spectra scope but mum has confiscated it like she knows how to use it…. 😆

Yes clearly mass spectrometry is out of the question 🙂

I could try measuring specific gravities maybe.. if the possible additives were always going to be the same.. hmm. Like, get engine oil and measure density with say 10% biodiesel added, then 20% then 30% etc and make a graph, then measure my sample and see how it changes. That would require me to use the same engine oil and the same fuel all the time tho.

I'm going to go with probably.

You'd have to make some assumptions though. Firstly that there are no esters in the mineral diesel other than those you think might be in there. Secondly that the only esters are going to be the ones you are looking for.

Rapeseed biodiesel will contain a variety of esters as the triglycerides in the rape seed oils contain different fatty acids.

I would go for adding some caustic (NaOH) solution and seeing if you get any soap formation. If this does work and you can lay your hands on some volumetric glassware then it may even tell you how much if you use a soluble indicator solution in the diesel and titrate. Of course the NaOH could react with something else that's in the diesel so you would have to make the assumptions above

Try whacking biodiesel into google. Look for some tests that would help you determine the purity of the biodiesel.

my only other thoughts would be gel/cloud point (biodiesel gels before regular diesel I think) or distillation.

I would go for adding some caustic (NaOH) solution and seeing if you get any soap formation

Oooh good idea.. like it… Also like the freezing idea. I could maybe just whack it in the freezer and seeing if it drops out as a solid…

I go on the veggie motoring forums a fair bit, but I thought I'd ask here first as they are mostly tight-arsed shed-tinkering motorists who are chuffed to bits that they have got something for cheap, rather than chemists 🙂

The reason I ask is that I want to run bio in my DPF equipped motor, and you're not supposed to. The reason being that the post-injection required to clean the DPF results in more bio entering the engine oil which a) affects lubricity and b) if there's any unreacted veggie oil it can polymerise the engine oil. Normal diesel ends up in the engine oil too but it evaporates, so distillation could well work too.

Bio also has a distinctive smell.. so if one could get some kind of chemical nose…

You could blend it. Up to B20 (20% Bio) is common enough. One of the main problems with running pure bio is that they put additives into normal fuels which won't be there in home brew bio. I think you'd have to be in a high mileage to see any £££ though.

Diesel doesn't evaporate very easily, not sure what temperature rapeseed methy ester would go at but you could google it. Polymerise your oil? What sort of oil is it? Silicon based?

Why do you think it will get into the engine oil??

Your main concern should be with what engine ou are proposing to run this in, biodiesel in common rail diesels for example can be a bad idea at to high a ratio due to the lubrication required for the diesel pump itself.

Very unlikely I would think to generate an accurate home analytical method.

Its likely you would get decomposition to a certain extent of mixing engine oil with caustic.

Ok so the car is a newer Passat with the DPF and common rail engine. It cleans the DPF two ways, one is raising EGTs and the other is injecting fuel into the exhaust stroke to be reacted in the first cat converter to produce enough heat to clean the DPF.

This post injection happens in a colder cylinder and doesn't get combusted, so fuel is more likely to end up in contact with the cylinder walls where it'll cool and make its way past the piston rings into the lube oil. This happens with normal diesel as well as bio but normal diesel, because of it's lower boiling point, vapourises more easily and exits via the crank case ventilation system. This is why the newer VWs have a no biodiesel sticker on them.

Having bio in your lube oil is bad for a couple of reasons. Firstly, it may affect lubrication properties but this doesn't seem to have shown up in tests. What's worse though is that IF there is any unreacted veggie oil in it and that gets to sufficient concentration in the lube oil it'll polymerise and **** your engine good and proper 🙂

So I reckon I can mitigate the effects:

1) If I do mostly or only long trips (as I do) the DPF can be cleaned reliably using raised EGTs, reducing the need for the post-injection.
2) Burning bio produces less soot – dramatically so for 100% bio as my own experience testifies – so again this should reduce the need for post injection.

So you see how I wanted to test the oil. A chap ran B100 on two identical DPF equipped common rail BMWs for a whole oil change interval; one only did short trips and the other only long ones. On the short trip one the oil was full of bio, on the other there was virtually none. I think he sent his oil away to have it analysed properly tho. You can just keep an eye on oil levels and see if it goes up, although this can be canceled out by the engine consuming oil normally..

BTW as for fuel in the fuel pumping system, bio has better lubricating qualities than dino diesel anyway so that's not an issue. What's more of a concern is the cold flow properties on startup.

I believe the proper mechanical solution is to have a two tank system which would eliminate the issue you are describing. Only yesterday I was talking to an operator at a "local" biodiesel production plant and the site director just bought a new A6 to which he has fitted a two tank system, i.e normal diesel for start up and warm up then switch over to bio.

I have thought about the density method and this would only have accurate results if the density of your two fuels were significantly different, but I would have thought biodiesel and fossil fuel diesel densities were fairly similar?

Scottie, twin tanking is for veggie oil not biodiesel. Veggie is a lot thicker than bio, and has a whole set of different problems of which twin tanking can solve. It's the DPF post-injection and subsequent oil contamination that's the problem, and that's not affected by engine temperature. You are getting a bit mixed up… I've done a hell of a lot of reading about this 🙂

As for the density thing, I did read that the density of bio isn't sufficiently different from engine oil for that to work, you are quite correct. It's biodiesel and ENGINE OIL that I want to test, not biodiesel and normal diesel.

Difficult test to figure out- everything you do to rapeoil to refine it takes out the things that make it stand out as rapeoil (free-fatty acids, phosphorus, soaps). (I work at a rapeseed crushing/refining plant btw!) The oil that leaves here for biodiesel is a dark brown viscous liquid with a bitter smell, but it's further refined off site before being added to normal diesel for retail.

Bio to me smells kind of sweet and.. well.. chemically.. I guess it's the methanol. And mostly that's the stuff made from recycled oil.

Rich, can you get me some rapeseed oil on the cheap? It's good stuff 🙂

I'd fill a bucket up from the refinery, but I reckon it would splash around too much in my car on the way home… 🙂

I was putting it straight in my old car.. rape was the best stuff too. Highest cetane value at any rate.

You are getting a bit mixed up… I've done a hell of a lot of reading about this

Well I dinnae ken then, you will have to engage the services of a professional.

Hey molgrips – great question!
You sound like you've studied this topic at length so anything I say maybe teaching you to suck eggs – apologise in advance for that.
My views on it are tho:

1. New expensive car with complex emissions control system and DPF regen system which says 'no bio'. I would NOT take the risk.

2. I don't know about the combustion of biofuels but if they have more impurities than diesel then perhaps you'll generate more ash in the burn which cannot be regen'd out of the DPF with increased EGTs.

3. It doesn't cost much to get engine oil sampled. Send away about 50-100ml of sample and get results in a couple of days for anything between about £10 and £40 depending on the tests performed and supplier.

4. Watching the dipstick for increase in sump volume would not at all be a reliable method for checking for fuel transport from combustion chamber.

5. If you do want to take the risk I would go for regular sampling for the first 6 months and maybe having the service interval as well…

6. If the biofuel which gets to the sump doesn't evaporate like diesel does it oxidise properly/efficiently/hot enough in the first cat (following post-injections) to regen the DPF properly?

7. I don't like modern emissions control strategies!

1. Well I reckon I know why they say no biodiesel, and I reckon I can mitigate it 🙂 (based on reading around, not just a hunch of course)

2. Bio gives much much less smoke based on personal experience with a slightly overfueled old IDI car I used to have. The overfuelling gave plenty of smoke on dinodiesel, but filled with B100 there was not a wisp.

3. Sweet

4. Agreed

5. I'm going for shorter oil change intervals too, there are also available special engine oils designed for use with veggie oil (ie not bio) that won't polymerise like normal oil can if it's contaminated with veg.

6. As I understand it, the cat is a catalytic reaction based on hydrocarbons and NOx, which I think there'll still be plenty of. The EGTs are I think lower when running bio, but I don't think that it'll be low enough to cause a problem.

7. Engineers never do, although I can't understand why. Surely low emissions are part of a proper engineering solution? What would you prefer, loads of crap pouring out of the back of your car everywhere you went?

My plan is to run a few tanks of B30 from Morrison's and do a test when I change the oil which will be in about 6 or 7 tankfuls time. I'm halfway through my first tank of bio and it runs and starts perfectly. The engine's a tad noisier though which I noticed on my old IDI too – it's more diesely, I put this down to the fuel burning more completely more quickly and generating a sharper shockwave in the chamber. I think the cetane value of the fuel is meant to be lower than pure dino diesel, but I am getting slightly better mpg which would add some circumstantial weight to the idea that less post-injection is requried for DPF regen.

2. Its not just smoke you need to worry about though. When engine oil burns the additives in it (including compounds of sulphur and phosphorus) generate ashes which cannot be regen'd out of a DPF – they will eventually clog it totally. My point was that if a biofuel has increased amounts of metallic or sulphur or phosphorous compounds for some reason then you will increase the amount of ash generated and will shorten the life of the DPF and reduce the fuel efficiency of the car.

5. Good!

6. I'm not sure here but I think you'll find there are various 'cat' stages. By definition you have a DPF. Also, if the car is using post injections for a DPF regen then there may also be an oxidation catalyst to oxidise the excess fuel in the exhaust and locally increase DPF inlet temp. If there is no oxi-cat then the post-injections are actually combusted in the cylinder to raise the EGT and therefore you don't need to worry about fuel transport to the sump! I'm not sure about the Nox reduction technology (does your car need urea/adblue?) but if there is a Nox cat then this is another consideration for poisoning due to ash from combustion.

7. Lower emissions are indeed part of a good engineering solution. However, all these anti-soot and anti-nox measures increase CO2 output which is also a very damaging emissions. Further, when being a hippy and considering the 'total life-cycle emissions' it creates a lot of emissions getting the platinum etc out of the ground to use in all the cats. Finally, and probably most pertinently, I don't like modern emissions control strategies cos it takes engine development away from the mechanical engineers and gives it to the chemists! No fun! My ageing TDCI does hose soot out the back on full power and it is a little embarrassing!

If you're noticing increased mpg and increased combustion noise then I'd say its likely that they are linked. If you've a faster rate of burn and in turn faster rate of cylinder pressure rise you will improve thermal efficiency and increase noise. Same effect as advancing the injection timing which in turn will actually increase your Nox production – there's always a trade off! Maybe that's another reason why they don't like bio. If there is a Nox reduction cat then if your combustion goes from low-nox-high-soot to higher-nox-lower-soot then maybe you will 'overload' the Nox cat? Post-injections should have a fairly minimal effect on mpg especially if your driving style means you don't need them much.

Finally, finally, this is a good company for oil testing. Will need to check with them if they can check for bio in the oil: http://www.alcontrol.com/specialist-businesses/oil-fuel-analysis-0

Only on singletrack…

2. Interesting – what's the life of a DPF? Have they worked on limiting the amount of engine oil burned to address this? How many DPFs are failing due to ash build up?

6. There is indeed a pre-dpf cat which reacts one NOx to another – don't recall which – and increasing EGTs to react carbon with another NOx in the process – which happens at lower temps than reacting it with O2. There's a good article on specifically how the VW DPF regen works, can't locate it now tho, even though it's reposted on many sites. They have a two-stage regen strategy.

7. Interesting this. In the USA NOx and soot are of high concern because of their ongoing smog problem, which is one reason diesels are not popular. In fact from about 2001 to 2007 VW diesels were too polluting to be sold in the US at all. With all these emission reduction strategies more diesels are now being sold which, when replacing a 25mpg car with a 45mpg one will contribute hugely to a net decrease in global CO2. Admittedly, different versions of the cars would seem to be useful. Having said that, the particulate matter from diesels really is very bad for you when you breathe it in – so it's a small hit on CO2 versus a big hit in city air quality. Which is more important? Who knows.

"Overloading" the NOx cat would surely just result in more NOx getting through? I must find that DPF article for you. Meanwhile, this is interesting: http://www.biodieselmagazine.com/article.jsp?article_id=2290&q=&page=1

EDIT: This is really interesting http://forums.tdiclub.com/showthread.php?p=2448720 but it's for US cars where they are really strict on NOx, it does mention that it's different for European cars. Impressive piece of chemical/mechanical engineering tho!

Oh.. I wonder if the increase in noise is because of the advanced injection timing enforced by the ECU to compensate for a slower burn? Although, found another article suggesting that the speed of injection would be different for different fuels due to the speed of sound being different in different media.. presumably fuel spray exists near that velocity.. a paper done by the US govt suggests that that alone results in an increase in timing of one degree. Hence increased noise and NOx I guess.

Good to talk about this from an engineering point of view rather than just the petrolhead one 🙂

Yo,

2. I'm assuming that the DPF has been sized for you car such that it 'lasts' the 'life' of the car. I'm defining the 'life' of the DPF as the usable time before the amount of ash builds up inside it such that the exhaust back pressure becomes far to high for the car to work efficiently. It may be possible to remove the DPF and vacuum or blow out the collected ash but there's not many places set up to do this (yet…). Indeed your car may be designed such that this just isn't possible. I would imagine that most manufacturers have had to do significant development work getting oil consumption as low as possible to reduce the rate of ash build up. Don't know of any published data about DPF premature clogging due to ash.

Overloading the Nox cat? Yip – more Nox passes through. Technically/legally speaking you could become emissions non-compliant but there's little effect other than that.

I shouldn't imagine that the ECU can tell that the combustion duration is longer or shorter due to biofuel. It controls start and end of injections to meter a known quantity of fuel. The end of combustion is not/cannot be controlled. Dunno what the mach No of fuel spray is… would be interesting…

You're clearly not a petrolhead! Biodiesel head maybe but that doesn't quite have the same ring to it…

Wow – I just skimmed one of your links. This jumped out at me:

Volkswagen tests using B5 and post-injection showed 45 percent oil dilution after 10,000 miles, but surprisingly no engine damage was evident upon inspection. “Using B10 at 10,000 miles surpasses that 50 percent threshold—and that is unacceptable,” Johnson said. “We want longer oil change intervals as a car company, so it’s hard for us to talk about this.” The implications are that increased fuel dilution due to biodiesel blends could lead to premature engine wear if oil changes are not done more often.

Terrifying…

Hehe.. there are a lot of bioheads out there but many are just trying to save money. Me, I like the symphony of machines and I also like saving emissions…

Don't ECUs have sensors to determine how far to advance the timing? Or is it just done by throttle position/load etc? I imagine it'd be kind of like a knock sensor on a petrol car.

I don't quite understand that link about 45% oil dilution.. after all we are all using B5 aren't we? Did the article say if it was 10,000 miles with continuous post injection, or just 10k miles of normal driving where post injection regen was part of normal regen strategy. Cos that'd depend on the trip length and driving style and so on.

Will be interesting if I do get the oil tested.

I think there are developments on the go for combined glowplugs and pressure sensors for closed-loop control but not sure if there are in production engines yet. ECU normally dictates injection timing according to pre-programme algorithm or map (look up table) according to a few sensors such as engine speed, throttle postiton, boost pressure, fuel temp, ambient temp etc.

I dunno about the specifics of the VW test but even if it was just diesel and not biodiesel dilution I would be most afraid. Used to set a limit of 5% dilution before got worried about drop in lubricity and viscosity. If they're getting 45% dilution over a normal drive cycle and standard production ECU map I would seriously question whether they have their emissions control strategy right. On that note, that's why you see a lot of heavy duty (truck) diesels running a burner or fuel injector actually in the exhaust pipe. Means they can increase EGT outside the cylinder and avoid all these durability worries we're talking about.

Yes, I think Peugot use a 5th injector in the exhaust manifold, which does seem a good idea. Tricky to implement with a mechanical injector pump but easy as pie with a common rail, so yeah it does seem a shame. Esp as VW used to be into biodiesel. I think it'll come soon.. VAG are new to CR after all.

To be honest I can't imagine that test is indiciative of normal driving. No way would conditions be that finely balanced. I mean B5 is normal fuel.. so you'd have to change your oil immediately on the interval and if your engine got older and had more blowby you'd be screwed. That must be a worst-case test.

To be honest I can't imagine that test is indiciative of normal driving. No way would conditions be that finely balanced. I mean B5 is normal fuel.. so you'd have to change your oil immediately on the interval and if your engine got older and had more blowby you'd be screwed. That must be a worst-case test.

You'd hope so huh… good luck with your experiment.
If the engine pops you should definitely strip it and publish the results as a good case study… 😉

I'll rebuild it. I've always wanted to strip and engine, so why not start with a cutting edge high tech one like that? 🙂

In all honesty I'll probably not have the car long enough to find out what happens. It's too big, not economical enough..