victore

Tried diesel engine oil in petrol Land Rover?

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A friend of mine having diesel Land Rover defender and using the diesel engine oil, claims that diesel engine oil is better than petrol engine oil. He highly recommend it same to me to due to it's very strong cleaning power that is as good as engine flush for petrol engines. Wondering if any of you guys ever heard of this experiment or using it? Is it really working?

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@victoreyour friend is right- diesel oil is perfect- for diesel engines.

The problem with using diesel oil in a petrol engine is that the additives in diesel oil are designed to deal with the combustion products of diesel fuel, which are vastly different from the combustion products of petrol, which why oil change intervals on diesels are so much shorter than on petrol engines, even after adding tons of additives to the oil.

Moreover, the additives in diesel oil can take up as much as 35% of the volume of the oil, meaning that you only have 65% oil in any given volume, as against the 15% - 20% of additives in petrol oil. Add to this the fact that diesel additives are not effective against petrol combustion products, and you end up using a lubricant in a petrol engine that only contains about 65% oil. 

Oil by itself does not lubricate an engine- that is taken care of by additives called "friction-modifiers", but in a petrol engine, the combustion products break down the friction modifiers in diesel oil much sooner than it would have done in petrol oil.

The nett result is that you lose the lubrication properties of the additives much sooner, and you have no way to prevent the formation of sludge because the detergents and solvents in diesel oil does not clean up petrol combustion products very well. 

Think of it this way- if car manufacturers thought that diesel oil would  worked as well in petrol engines as it it does in diesel engines, they would not have prescribed petrol oil. Using diesel oil in a petrol engine is not a good idea.

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Don't make experiments with oil. Stick to manufacturer recommended grades and service intervals. It can only take one bad fill of oil and you're taking an engine apart to change piston rings and shell bearings. 

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I heard this story few years back from am Arab friend,  whose was using this diesel engine oil in petrol engine and also praising it. not sure what happened after that.

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I had a friend who had the same LR Discovery 1, 1998 model that I had.

He had read about using Diesel Oil in Patrol engines and decided to give it a try, the Diesel Oil is thicker than Oil for Patrol Engines. i was in touch with him for 2 years and he was all praise about it and in 2 years nothing seemed to be effected in a negative way, he found the ride to be smoother and at the time of oil change it came out very clean. he changed the Oil every 7000 Kms.

I had thought of doing it on my LR Discovery and I knew a mechanic who used to deal with LRs only, he was game too to let me try this out, but recommended as the Diesel Oil is thicker to start using it in the Summers. However as my car got sold before it had a chance to experience another summer that idea was scrapped.

He did use a particular Diesel Oil on his rig, let me check if I can find his number and check with him if he is still using it and what is the type he is using.

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I quote my fi

My motor is very smooth but this could be also attributed extensive highway driving aswell, but I think the additional detergent qualities of diesel oil might have helped aswell. I think my motor has atleast kept its power level if not gained some over the last 100 to 120,000kms which I have clocked over since I switched over. Now the disco is sitting at a grand total of 301,000kms. After the intial switch over I popped a few extra leaks. This was one of the symptoms to expect in a older motor and sludge and gunks acts like putty and patches up holes. But the the added cleaning qualities of diesel oil will break them up and dissolve them. So I took that as a positive sign as that it was doing something in there.

For the pro and cons. Not all engines are flat tappet design and I don't think anything post early to mid 2000's is anymore. But this flat tappet design was carried over into cars already using that design until next gen changes. Like Range Rover took it up till 2003, discovery upto 2004, Cherokee up to 2001, Jeep wrangler till the demise of the TJ wrangler into 2006 until the introduction of the JK with the V6. BTW I have no first hand info the newer jeep V6's used inthe liberty/cherokee/grand/wrangler that this motor is not a flat tappet design but I am assuming it isn't. Better look that up if your in doubt.

And the biggest added advantage for me who was up until recently changing oil every 15 days was it was very cheap. 45 bucks a gallon. The oil every change cost around 60 dhs. Although Shell rotella diesel was strongly recomened every here and even cheaper at 43 ish bucks for 5 liters. But I choose not to use that because of the lack of appropriate S ratings on the box. S followed by another alpha bet like D,F,G etc etc stands for Spark i.e spark driven motors i.e petrol and there will also be a similar C rating with the C standing for combustion i.e diesel motors. And the shell available here only has a C ratings and no S 

ZDDP was removed from engine oils as stricter emission controls came into play as if any manages to get past the pistons rings into the exhaust ( i.e : cars burning oil ) could damage the catalytic converters so was removed from Engine oil.

The most common question that is asked, viscosity. The viscosity is exactly the same as regular engine oil a 40w diesel engine oil is exactly the same viscosity as 40w petrol engine oil. Like 1kg of sand and 1kg of metal are both 1kg, right The SAE API standards are same across the board.

As per milage I do get much better milage on the thing when compared with people with similar cars. And I believe my very relaxed driving style and general good shape of my motor are more contributing factor than anything else. Power I've out run 04 discoveries with less than 50k on the clock and can give more sedans a run for their money If I choose to gun it. The other day a JK was struggling to keep up on a traffic light drag run :D Anyway no solid statistics on anything just feel of the butt assumptions.

Personally I do believe it keeps the motor is very good shape and certainly does improve engine life. Think of it as cheap synthetic oil which the best comparison. What kills oil ? Heat is what breaks down its molecule chains and it loses viscosity and loses it friction protection qualities. Diesel engines run much hotter than petrol, almost twice the internal temp of petrol. Diesel oils are made to withstand than. 

Also Diesel engines run much more dirtier than petrol meaning produces much more soot and deposits, and diesel oil is formulated much more absorbent and detergent additives and qualities.

What does synthetic oil do. Is more resistant to heat and more cleaning and absorbent qualities. Diesel oil when running in a petrol engine does exactly that. Some newer high end luxury cars are now being recommended by manufacturer to use synthetic diesel oil. 

And all for all. Engines with flat tappet design need ZDDP no doubt about it whether you choose to use a ZDDP additive or diesel with added benefits. As slowly your wear out your tappets and loose power over time. Almost all high mileage motors running regular oil have wear signs of worn tappets and cam lobes.

I use ADNOC HDSP Diesel Oil, only because it is the most convinient and AD petro products are of much better quality than other localy made products

Just a pointer when you are checking the ratings any alphabet after the S. The higher the alphabet the better the quality. Example SB would be better than SA. I think ADNOC HDSP is SF or SJ. I'm not current on these ratings but I think SJ is the highest out there.

You could if you wish use Diesel oil upto 10k kms and be fine but as I said before oil is cheap engines are not. And fresh oil is always better than half life used oil. Hence I also never recommend using any oil, wheter synthectic, diesel, or regular for more than 5k, 3k if you go for desert trips alot and specially in the summer. 

I was talking to a engineer in shell once and he himself told me their regular petrol use oils are formulated to be used very safely up to 7k but recommened changes after 5k as you really don't want to squeeze out every drop of life from it. Trying to save on a few bucks on cheap oil you will end up doing more expensive harm to your engine.

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phew, such a long read and sound totally convincing and tempting.

Sorry but what if it's all fake n fabricated story? Just for fun?

If it's true, why not everyone is taking and why none of the car manufacturer adapting to this high temp, extra cleaning logic?

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Hi Amitaj, I was just sharing an experience which related to the question you asked, however if you feel any of this is unreal than why ask on an open forum where you don't know anyone. Wouldn't it be better to ask among the circle of known people who have been through this experience.

Truth is we are all trusting the car manufacturers and their recommendations, but how good are we really at being mechanics, 90% of us just buy a car and drop it off at dealership or service centers and we don't even bother to ask what needs to be done or what is being done. To most of us service means oil change, filter change, plugs change, air filter change at certain intervals, however a car is so much more than that. Car manufacturers and other service centers are backed up and supported by certain companies including oil companies and they will in turn support those companies.

The experience I have shared is what I have seen with my own eyes and not something which was just copied and pasted from a website which I googled up. I am part of an off-road fraternity and I had a very good friend within that community who also owned a LR Disco 1, 1998 model. He used to have very long drives as he had to travel to Abu Dhabi twice a day from The Gardens. If you have read the whole write up you would understand his high mileage now. He did exactly what you asked for 5 years back and I was just posting his experience to help you decide.

In conclusion I would like to say that I have shared an experience which is related to the question you had and its totally up to you to believe it or not. Whatever your decision, I wish you all the best for future.

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@amitaj everything shared on public forums should be taken with pinch of salt whether you believe or not as there is no 100% authenticity of any information unless it follows your chain of trust.

Rahim bhai this experience is of junaid right? who is very old member here @desertdude. Knowing him personally for so many years and he was my first off-road buddy and hard core LR and offroad fan, I can vouch for his words and experience man.

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You are right Gaurav Bhai, this is from Junaid's experience. Whatever I have posted here is his exact words and I have seen him put the Diesel Oil in His Discovery and noticed the difference, unfortunately when it came time for me to try out the same after seeing him use it for 2 years or more my Disco got sold and I never got that opportunity.

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