Low viscosity fuel oil (Petrol added to Diesel)

[ericmark]

My wife decided since Petrol was cheaper than Diesel to fill up with Petrol. And as one would expect problems resulted. So most of fuel was drained out and it was refilled with Diesel.

However I started to wonder since it is the viscosity which causes the major problem one expects around 35 sec if instead of draining Petrol I had added a gallon of engine oil would this have worked?

Clearly at the price of engine oil one would not normally do this. But would it have saved me all the problems of removing the Petrol / Diesel mix?

 

[^woody^]

Diesel works by being heated under compression, so no spark like petrol engines. So its not just about viscosity

You can do it the other way around by thinning diesel with a bit of petrol ... for when its cold weather

 

[ericmark]

So pinking is the real problem being such a high compression ratio. I know during the winter because paraffin is not taxed but petrol is adding petrol to diesel in a small quantity is permitted to stop waxing.

Also to start the old Lister one filled the inlet with a measured quantity of oil to temporary raise the compression ratio.

Now all up and running again so only academic but just wondered if it would work?

 

[Peter.N.]

The problem with putting petrol into a modern diesel is lack of lubrication, the petrol will burn OK but could cause damage to the pump and injectors if its a common rail engine, but, yes, adding some lube oil to the mix would lessen the chance of any damage.

Peter

 

[ericmark]

The problem with putting petrol into a modern diesel is lack of lubrication, the petrol will burn OK but could cause damage to the pump and injectors if its a common rail engine, but, yes, adding some lube oil to the mix would lessen the chance of any damage.

Peter

Interesting reply is a common rail the same as the PT system used with cumins engines? Did my training many years ago left motor trade in the 80's so not into the new systems.

Seem to remember the compression ignition engine we use today works on the Carnot cycle and the orignal diesel engine ran on coal dust which makes one wonder why we call it diesel fuel or a diesel engine?

I seem to remember we had Bedford TK's and these could have a DPA pump or with military version a Simms pump and the latter was considered as a multi-fuel engine with the pump having to have it's oil changed at regular intervals like the engine. We always used diesel but the book gave a whole range of fuels it could use.

Also the Mann engine I worked on high revving 300 rpm on board ship would start on 35 sec fuel then turn over to heavy fuel oil once running seem to remember it being a 2 stroke but a long time ago. So it would seem engines can run on a range of fuels.

What I think matters is the Cetane rating and the lubrication quality and the viscosity of the fuel clearly adding oil would enhance the both lubrication and viscosity but not sure what it would do to the Cetane rating?

With dotty women like my wife putting petrol in cars instead of diesel to know what could be add to bring the fuel back to a usable quality would be very handy. It would save the problem of draining the tank and re-filling.

I could not really have the car off the road while I found out the answer but it still seemed worth some research should it ever happen again.

Maybe one can buy something with for example Alkyl nitrates and oil specially designed as an anti dotty women additive? However not sure how one would work out the quantity required. Likely some tube with small hole and a stop watch?

 

[Peter.N.]

The DPA pump as you say would run on practically anything, I used to do diesel conversions using the Perkins 4/99-4/108 engines which used the same pump, albeit the four cylinder version, the difference with modern engines being that they use something like ten times the injection pressure of those old IDI engines - so you can see why they are a bit lubrication sensitive.

Peter

 

[ericmark]

I thought 175 atmospheres was bad enough ten times that's 25,725 lbs/in² no wonder they need the lubrication.