You might get away with this on an older 20+ year old diesel, but UNDER NO CIRCUMSTANCES do it on a high pressure common rail engine. About 10 years ago I absent mindedly put 2 litres of petrol in my 2013 vauxhall. I thought if I filled the tank it would amount to 5% petrol in the diesel and it would be ok. It did run, but even after several refills with diesel, it ran rougher and fuel consumption was down by about 10-15%. Modern common rail diesel pumps run very fine tolerances and use the lubrication in the diesel to lubricate. 5% petrol was enough to damage this lubrication effect and wear the pump.
There is often lots of traffic on Land Rover forums about adding small amounts of 2-stroke Oil to diesel to help them burn cleaner. Lots appear to swear by it, but as has been said several times on here doing anything like that to a modern Common Rail Diesel with EGRs etc has to be a risk. As an aside, if using 2-stroke Oil in a Diesel, or even petrol, consider the difference between motorcycle and Marine(Outboard) grades. The marine grades are far more expensive, but formulated differently as they are designed to work with outboards that run cooler and spend long periods of time running at constant speeds using 1/2 to full throttle.
Yes I was warned not to add anything to common rail engines. The Suzuki wasn't commn rail (Renault Megane engine I believe). It was very prone to dpf fouling and I used it off-road which made that worse. I actually did it first time by accident. I put four litres of petrol in it before I realised. I brimmed it with diesel and hoped fror the best. It ran great. Went better and no sooty smoke which it was terrible for when run on regular supermarket fuel, especially after dirving slowly off-road. I mentioned it to a mate who was a very good mechanic. He told me about avoiding additives in common rail engines. He said petrol does help reduce fouling and dpf clogging because it makes it burn hotter and cleaner buut it time can wear the valve seats because it reduces the lubricating effect of the diesel. He recommended paraffin which is basically all the much more expensive dpf cleaning additive is. I learned online about the 2 T oil. But it had to be a specific grade, not any old cheap stuff. I used to add one single dose mini bottle of Stihl red chainsaw oil to every 50 L of fuel. That worked very well.
Any of you UK scribes old enough to remember the days when every garage had a Redex dispenser by the pumps ? A couple of squirts per gallon provided upper cylinder lubrication for the petrol 4 stroke. Acquired such a dispenser around 60 year ago filling with diesel for the same purpose and many a mile later on the '55 250 BSA, '64 200 SS Ducati and all that was to follow never had a problem, mind you those days ethanol use was as a paint solvent and disinfectant. Now that petrol and diesel contain ethanol the addition of diesel or old engine oil in the steel tank of a stored bike will help to overcome the hygroscopic nature of the ethanol rusting the tank's base weld.
Aye Chris, as an auld time hack I did indeed add a pint of petrol to a gallon of diesel for the LandRover. With winter temperatures frequently 20+ deg. C. below in the Cairngorms the diesel was like jelly and to thin the fuel further for lower temperatures I'd roll up newspapers to make a flaming torch to heat the underbody fuel line. Paraffin would have been the better additive, withstanding the compression bettor than petrol but not so convenient. Incidentally back then I flew control line model aircraft with a range of high revving 0.5 to 3.5cc diesels with a fuel mix of Ether, Paraffin, Castor Oil and a variable dash of Nitro Methane, all components from the village chemist but for the paraffin, from the garage, whose main purpose was for the Tilley lamps fired up during power outages.
Those were the days. I used to make a mix just like that to run a tiny diesel RC aircraft engine, the proper diesel (not the glow-plug one which is also technically a diesel) with the compression adjuster you used to back off once it'd started.
I always used to put a small amount of fully synth oil in the petrol tank of my Ducati's back in the dim mists of time. No more than a table spoon or two. Never experienced a problem and it made me feel like i was doing the engine some good.
Used to run my old Isuzu fully on vegetable oil with no problems. But I would be very wary of any additives on modern common rail engines.
One of my mates used to put a shot of castrol R in his tank - could have been early ZX10 2004 or TL1000s. The smell was great when I was trying to keep up.
