What best to maintain a Greatwall Wingle engine and performance?

Diesel Knock is an injector issue.

https://www.google.com/search?q=Mazda+Bongo+RF6C+engine%2C+turbo+diesel+and+it+has+a+diesel+knock

The DPF status light is flashing.

It's telling you a parked regeneration is necessary, and you need to perform it as soon as possible. If your Check Engine light comes on while the DPF status light is flashing, it means you need to perform a parked regen right away.

DPF Lights ' What to Look for When They Come On

Tracey Road Equipment
https://www.traceyroad.com > dpf-lights-what-to-look-f...

..
Some are different makes and models but the reason is the same

no country told no year told, no maker told (3 strikes/)
2010- UP. and 2 diesel engines,
this
2.0 L 4D20 I4 (turbo diesel)real name.?
we have no car here USA, like this
is this DOWN under cars?? Steed?

google hints at

Great Wall Steed Australia wiki says ITALY./
welcome to a global www open public forum
where are you matters for sure cars tech.
for tech, books , and parts (bits) and not wanting wrong parts
buy the service manual in your country for these steps
google hits are zero. it is China made car, GW4D20

what did you soak them with ? not sure what you call where you are but in the UK I've used a household cleaner called CILIT BANG, the degreaser one, has worked everytime i've tried it

Dodge Cummins Error Codes List - Diesel Bombers

www.dieselbombers.com > Dodge Cummins > Dodge Diesel Tech Articles

Apr 6, 2009 - It appears to have every CEL code known to man... or at least known to Dodge. ... Chevy/GMC Truck and Duramax Turbo Diesel Forum · Chevy/GMC Duramax... General · 2011 · 2013+ · 2007.5 - 2012 LMM · 2006 - 2007 LBZ .... P0039 Turbo/Super Charger Bypass Valve Control Circuit Range/Performance

Best I can tell this is a diesel truck? I know diesel, but
depending on age could be injectors, possibly Diesel injection pump hopefully not. The fuel is black? Someone is putting old engine lubricating oil in the fuel tank. It will increase the problem of black smoke. It may also have a bad smell because of the engine oil. If the turbo is not spinning properly (high pitched whine) the bearings may be bad and it's not getting enough air into the engine. This would also explain the smoke problem. Take it to a Diesel specialist!

diesel engine ,well it doesnt matter i use turbo diesel oil for all the vehicles i service ,and the best oil around as far as iam concerned is the shell rotella great oil this one it was fitted in all ford engines when i worked on the assembly line in dagenham 40 yrs ago .change oil every 6000 miles and a oil filter every third oil change and this vehicle will never wear out

the golf is renowned for a 1/2 sec lag in the turbo (except for the diesel which is quicker and more powerful all round,2 secs faster from 30 to 60.)you could chip the car (volks tuning) and make it much better...if you had a clutch problem,the engine will spin,wheels would be stationary.....

go to any auto parts store, like an auto zone and tell them what you are driving. They have a data base which will guarantee that you get the exact oil that you need.

I use Mobil Delvac 1 ESP 5W-40 , a fully synthetic supreme performance heavy duty diesel engine oil that helps extend engine life while providing long drain capability and potential fuel economy for modern diesel engines operating in severe applications. Mobil Delvac 1 ESP utilizes state-of-the-art technology to deliver exceptional performance in modern low emission engines, including those with Exhaust Gas Recirculation (EGR) and Aftertreatment systems with Diesel Particulate Filters (DPF’s) and Diesel Oxidation Catalysts (DOC’s). Therefore we believe it will be a good oil for the high mileage vehicles with the proper care for your vehicles as recommended by your manufacturers' guidelines.

Possible oil sending unit problem.

hi, this problem could be valve stem oil seals these are cheap to buy but will require the top half of the engine been stripped and rebuilt.
If the car has a turbo then you might find that its just a turbo pipe split this is often the case on most cars that have turbo as your is diesel then you should have a turbo. This would be my first choice to get looked at as usually its just a pipe to the turbo has split and this causing the problem your having. Replacing this should not cost to much as it is common problem so look at this first.

Worst case it could be the turbo needs replacing but getting a garage to check this for you is the best bet but hopefully it is just a split pipe going to the turbo.
Most diesel cars with your problem that i have worked on is usually one of the pipes for the turbo has a split in it so replacing this will solve your problem ok.
let me know if you have any problems or questions and ill be glad to assist you ok.