Oil/Diesel Mix for better fuel economy

The only reason that a mining company would be putting old engine oil in the fuel is to reduce fuel costs and be seen to be environmentaly friendly. When I was working for BHP years ago in the coal they were doing it. It doesn't give 10% better fuel economy. If anything economy goes down because old engine oil is less efficient than diesel.

If you own a diesel and you want more power than add a turbo. If you want better fuel economy than put a brick under the accelerator and stay in the left lane.

Several large truck manufacturers now use a system of slow but continous oil changeing while driving. A small amount of engine oil is bled from the engine sump into the fuel system and at the same time (and at the same rate) new engine oil is bled into the sump. The truck never needs an oil change, just change the filters and no waste oil to get rid of (just a bit more air polution).

Some trucks and earth moving machary do this.
Have heard of one civil contractor who has a feed from the sump into the diesel fuel line to the engine. The engine oil is topped up from an oil tank. This saves having to do oil changes on site, in which case it has to be done in a catch area etc., and the oil disposed off properly.
It really only works well once the engine is really warm, so the oil burns well with the diesel. It would be a smoky engine if there was a diesel/oil mixture in the tank on cold startup.

PS - Did look at this myself a while ago, thinking even if I could put 2 to 5 litres of old engine oil in ecery 150 litre tank, it would solve two problems, disposing of the sump oil after a change, and extend the fuel economy!
Decided not to do it on advice from a few on this site.

Accidentally put around 10% unleaded in my diesel tank once before waking up and realising what I was doing. Decided to leave it and see how it ran as I had heard of this practice before. Can't say that it made any noticeable difference while driving and still got around the same distance on a tankful. Haven't tried it since, but I would need a bit more convinvincing to do it on a regular basis.
Gerry

Using waste oil in diesel is not new. About 10 years ago, I built a unit to filter and meter waste engine oil into a diesel power station fuel supply for a mining operation. Slug dosing into a diesel tank causes problems, so it has to be metered and mixed. Proper filter selection is important. Cummins and Caterpillar, at the time of my research were happy to see a maximum of 5% oil in fuel. We calculated that our dose rate would be a maximum of 2%...a good safety margin!

Crankcase and hydraulic oil were regarded as fine, but definitely not transmission oil. I do not believe there are any efficiency benefits, apart from utilizing the waste oil. I often consider doing this on my own vehicle, but it's under warranty. If I still had my old Rangie with Isuzu diesel, I would do it in a flash, I reckon.

Using petrol in the diesel can provide more power, but it will shorten the life of your engine. Truckies who did this usually put it in the boss's truck, not theirs! (Otherwise they learnt the hard way.)

Regards
Brid