In a standard aircooled engine, the oil needs to be changed every 3000 miles, so bear this in mind before a long trip such as the cruise down to RTTS! If you have covered more than 2000 miles since the last change, it's time to do it before a journey like that!

Air-cooled engines rely on the oil for cooling, as they don't have a radiator or water to cool them down, just a fan and a sump of oil. If it's not very fresh then your engine will suffer: don't just top it up - change it!! It will only cost around £10 for a 5ltr can of oil and you only need a 10mm spanner and a 19mm spanner as well if you have a centre drain plug, a gasket set will cost you around £1-£2. You only need about 30 minutes for the job. It really isn't worth paying a mechanic to do a job like this unless you have a phobia of oil!!

Go for a quick drive to warm the oil a bit; it drains better when its warm.

Jack the rear end of the car slightly, but only enough to gain access. If its a bit low, the engine must be near horizontal for it to drain properly. Look for the round sump plate on the base of the engine in the middle, and undo the six 10mm nuts..[or the single 19mm nut first if you have the drain plug type plate]. As you undo these, oil will drain out , so be prepared with your drip tray!! Removing the oil filler cap at this stage can help with fast draining too.

Once the oil has all drained, remove the sump plate and the strainer which looks a little like a tea strainer above it. Bin the old oil gaskets and start cleaning! Clean the strainer with white spirit, thinners or paraffin. You need to get everything you've taken out clean and free of dirt, grit and old oil. Sometimes you'll need to swill the strainer a few times with thinners to get it clean. Once all is shiny again, get the new gaskets, put them between the engine and strainer, and between the strainer and baseplate. This can take some getting used to; it feels like you need two pairs of hands the first time you do it! Then, bolt the whole lot up with the 10mm nuts again, not forgetting the little copper washers that come with the gasket kit or you'll get leaks! Torque them up one by one, opposing sides but don't tighten them up too much. They only need to be done up to 6ft/lbs [firm but not tight!]

Once this is done, you can start filling up with fresh oil. You'll need to add approx 2 1/2 litres for a standard engine. For the best oil to use, see the oil article. Fill up with the new oil until you reach the higher of the two marks on your dipstick, turn the engine over a few times , allow the oil to settle, then re-dip for a final reading. Add oil if necessary. Pop the cap back on and thats it!