Failure to do this can result in many issues, such as transmission overheat, solenoid failure, jerky gear changes and even total gearbox failure. A transmission fluid flush is a process in which the fluid in an automatic transmission is flushed out of the transmission (gearbox) and replaced with new Automatic Transmission Fluid (AFT). What motor oil should I choose for my CITROЁN C4 II Grand Picasso 1.6 BlueHDi 120 Diesel 120 hp? Our top-rated products that suit CITROЁN C4 II Grand Picasso 1.6 BlueHDi 120 Diesel 120 hp best are: Engine Oil PEMCO 332 0W-30, 5l; Engine Oil BIZOL TECHNOLOGY, C2 0W-30, 5l; Engine Oil FEBI BILSTEIN C2 0W-30, 5l Oil Viscosity Classification SAE: ATF III Recommendations: Allison C4, Dexron III H, Ford Mercon V, Honda ATFZ1 excl CVT, Hyundai SP II, Hyundai SP III, JASO 1-A, Kia SP-II, Kia SP III, Mazda ATF M III, Mazda ATF M-V, Mitsubishi SP-II, Mitsubishi SP-III, Nissan AT-Matic D, Nissan AT-Matic J, Nissan AT-Matic K, Toyota Type T-II, Toyota Type T-IV Carefully remove undertray. It is heavy. Here's the sump plug. Don't forget to place a suitably sized receiving tray beneath. Using a 21mm spanner or socket, carefully remove the sump plug and fully drain the oil. When the sump has emptied, wipe clean the sump plug area with a paper towel and fit a new sump plug and washer. Do not over tighten. The recommended transmission fluid for a Citroën Xsara Picasso with a manual transmission is 75W-80 synthetic gear oil. For a Citroën Xsara Picasso with an automatic transmission, the recommended fluid is Esso LT 71141. It is important to check the fluid level regularly and change the fluid at the intervals specified in the owner's manual. I called my local Independent Citroen Specialist to enquire about an interim oil change for my C4, 2.0Hdi (with particulate filter). He quoted £60 and when I asked what oil he used, he said 10W40. I mentioned that Citroen now specify a particular grade ECS oil for diesel cars with Particulate filter and his reply was that this was unnecessary I did exactly the same on my previous 2014 C4 Picasso, doing exactly the same thing too. I left a drop link connected, and knocked the suspension strut, so it pulled itself toward the back of the car (because of the suspension spring) and pulled out the driveshaft and dropping a large puddle of oil. Illustrated step-by-step manuals and video tutorials on replacing CITROËN XSARA Gearbox Oil and Transmission Oil will tell you how to carry out DIY replacement of parts and maintenance of your car quickly and cheaply NhVRs89.