For 1991 Kadett Hatchback E facelift Opel recommends to use: API GL4, and SAE 80W transmission oils and genuine OEM transmission oil with a part number: 90001777. To select the right transmission oil see the table below.
How much transmission oil you need to put into 1991 Kadett Hatchback depends on the engine installed, and some other conditions listed below.
Manual transmission oil replacement for your 1991 Opel Kadett Hatchback can be done on your driveway. The whole job will take about 30–60 minutes and will save you around $100.
There are two plugs on the transmission - the drain plug at the bottom, and the refill plug on the side. First step is unscrew the refill plug, and then unscrew the drain plug. Use a spanner or a retched with the correct size head. After oil came up screw the drain plug back with a new gasket. Then refill the transmission with new transmission oil.
Please be noted that all capacities listed here are approximate. Check fluid levels when adding or refilling as recommended in your 1991 Opel Kadett Hatchback user's manual. Keep in mind that all information here is provided “as is” without any warranty of any kind.
Before doing any DIY service please check your insurance policy and Opel warranty policy for your region. In some regions DIY service may invalidate your warranty.
DIY car service is not as difficult as it looks like and it might save you thousands of dollars per year. It might be even fun and a good thing to do with your kids on a weekend to teach them how basic machinery works. It's really hard to screw something up and damage your car permanently if you use right tools, follow Opel Kadett Hatchback service manual and use right parts and fluids in prescribed amounts. Even modern cars stuffed with electronics can be serviced in your garage or even in your driveway. Changing engine oil, brake fluid, ATF, replacing brake pads, and etc. It's all may be done by yourself in a mater of a couple of hours.
Doing basic service for your 1991 Opel Kadett Hatchback you're not only saving money, but also also improving your technical skills and learning something new.