What causes oil and diesel mix in engine

Where are you finding this? Diesel and water would normally only mix if water was getting into the fuel tank. Are you sure it is diesel? If you are finding it in the coolant reservoir it is more likely to be engine oil. This usually suggests a blown head gasket.

No do not do that you will ruin the fuel system and damage the engine!!!

TWO answers read and follow the Manufacturers Specification. OR Always use ** 15-40 Diesel Rated Oil is ALL gas, natural/propane and diesel Engines! Use Purolator, then WIX, then Manufacturers Filters - NEVER Fram, "special". oil the oil lube shops filters!!! WHY? When flying planes, every 100 hours I remove the filter, cut it open, and INSPECT the filter material for particulate. My Vehicle Engines go for well over 600,000 miles - most other peoples. simply do NOT!

** I use Delo 15-40 in everything - an better one is Shell Rotunda, however too expensive and not needed! In gas engines after 500 miles, the FIRST Time ONLY - Replace the oil AND FILTER - mixed fuels and oils NEVER mix well. Then on gas engines ONLY replace the filter at the "normal" intervals and ADD not change, the oil... On Diesels, due to the extreme compression, you DO change the oil, at "normal" intervals. In gas, NOT diesel engines - you could use Pep Boys and/or Walmart's generic DIESEL GRADE oil - NOT in diesel engines, as from my experience.

AVOID gasohol - unless you like flash rust and oxidation inside your engine AND 30% less fuel mileage - NEVER use WD40 on ANY metal you want to reuse! And do NOT use BP or unknown small time gas stations - as MANY "top off their fuels" with other octanes - which LOWERS the octane - do to "covalent bonding of carbon molecules" Example: a 50/50 mix of 100 octane with 90 = closer to 80 NOT "in the middle". LEHenson.com

No need to mix oil and diesel since the diesel fuel itself provides lubrication to the internal fuel system parts. If you put oil in the gas tank, expect a huge amount of white smoke from the exhaust pipe until the fuel tank goes empty.

Its sounds like you're priming pump has a leaking oil in to fuel line

Hi John, These days most oils are formulated to be used in both petrol and diesel engines but those formulated specifically for diesels should not be mixed. If your talking of a top up I suggest a flush with a good quality chemical and a lub service. If you have had a service carried out and changed the type of oil the same applies. Mixing oils can cause fast sludge build up which can block the filter, oil pump and galleries. These days most oils are designed to run both types of engine, but mixing is neve a good idea. Regards John

the injector are along top of engine , the lines all run back to a pump usually attached to engine side, only unit with multiple metal tubes running out to engine top, removal of injectors requires some special tools. this requires good diesel knowledge and tools to repair either one.

Need more input here iam afraid ,like make and model and where the leak is if the fuel is mixing with oil do not drive it could hydraulic or even worse run away with itself and just run till it blows up ,once it goes turning the key off will not stop the engine it will run on the sump oil mix and watch a con rod come through the block

Hi Marsha, Many people mix brands of oil specified for either petrol engines and the same is true for oils specified for diesel engines if topping up, but it's not a good idea....It is a very bad idea to use an oil specified for one type of engine in the other. I would suggest never mixing oil manufactured for a diesel engine in a petrol engine or visa versa. The reason is that the diesel engine is dirtier than a petrol engine and manufactures of oil formulate it to have more cleaning chemicals than that used in petrol engines....Mixing the two can result in a build up of sludge which can actually block the lubrication system of the engine causing in some cases severe damage. Regards John