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Engine Oil Maintenance

Engine Oil Maintenance

You will see oil changes mentioned here, and all through the forum. We thought it might be an idea to have some generalised info about oil.

How often should I check my oil?

You can never check the oil level too often! I check mine every single day, as part of my pre start routine.

Use the dipstick, that's what it is designed for. Pull it out, wipe it clean, and put it back in. Then pull it out and check the level, which ideally should be between the 'Max' and 'Min' marks…In fact, it's often marked as 'Level'! And, level is what the vehicle should be when you check the oil, or a false reading will result.

NEVER run the engine with the oil level below the minimum mark! There is then not enough oil in the sump to supply the top of the engine, and still have oil in the sump. Expensive damage WILL result.

A bit of chemistry…

ALL oils, regardless of type, are constructed of long chains of molecules which get chopped into shorter chains in a running engine.

This means that oil loses its viscosity after time, and loses its ability to protect the moving parts of the engine with its slipperiness. When this happens, it is time for new oil.

Don't worry if the oil is starting to go black, it does this after a few hundred miles of being put into the engine, it doesn't mean it isn't working properly…. In fact it means quite the opposite. It means it is working as it should, collecting oxidised oil, flakes of carbon, and tiny particles of metal from hard working parts of the engine.

So, how long should I leave off changing my oil?

Well, in truth, you can never change your oil too often! The more regularly you do oil changes the longer your engine will carry on working in the way that it should. Of course, you have to draw the line somewhere…you wouldn't want to change the oil every 100 miles, now would you?

Manufacturers will tell you that you should change the oil every 10,000 miles… I change mine every 1,500. Somebody else will say its 3,000 miles…. And some handbooks will say 6,000. There are a large number of imponderables at work here, and you have to strike a happy medium.

During the running of an engine, large amounts of moisture are formed and depending on the state of the engine in particular (ie, wear and tear) some moisture will inevitably get into the crankcase and sump. Most of this is taken care of by the crankcase breather system, but in cold weather a LOT of condensation will take place. Add this to short journeys, and you see the beginnings of a problem. The water/condensation mixes with the oil and this water will dissolve any nitrates formed during the combustion process, leading to a corrosive compound working its way into all the moving parts of your engine. And that can't be good, can it?

Short journeys are bad for engines…they don't warm up enough to 'dry out' the condensation. It isn't so much the distance travelled, as much as the length of time the engine is run… So, by that rule we can't really say to change the oil by mileage, if you do many short journeys.

Other factors again cause you to wonder when to change the oil… For an example, the state of the engine has a lot to do with the answer. How much wear in the bores, say. Blow-by of gases past the piston rings will make the oil drop efficiency quite quickly.

The average vehicle will do 10,000 miles a year, say. Given that 1/3 of the year is winter and 1/3 is summer well, a change every 3000 miles would seem to be indicated. One third being cold and damp, one third summer, and one third sort of in between… (Or cold and damp. It is Britain I'm living in) 3000-4000 miles would seem to be a good average. Again though, that depends on you. We don't know how many miles you do every year!

I changed the oil, and put too much in. Now what?

Well, I would suggest you drain it back out. Why?

Well, if you over fill the sump a couple of things happen. Start the engine, and the extra pressure in the crank case, and the oil pump etc will place extra pressure on the rear main bearing seal. Eventually (and faster than you might think) the seal will fail, and the oil will find its way on to the flywheel. That can cause clutch slip and is generally not a desired thing.

So, if that goes unnoticed (unlikely, but you never know) the front seal may well burst too. That is messy.. It leaks onto the engine, gets sprayed about all over the engine bay by the crank pulley, often all over the front axle, the fan/alternator belt and the bonnet. It runs down the sump, onto prop-shafts… Yup. Messy. (Okay, sounds a bit melodramatic maybe…but I have seen it)

There's worse… Inside the engine, the oil level is above the bottom level of the crankshaft. It is getting splashed about by the crankshaft, and is probably getting frothy. Frothy oil is not good. It is aerated, and that's not ideal. Air is not a lubricant, as your main bearing shells will soon testify.

So, to summarise…

Check your oil regularly.

Check it with the engine cold, preferably. At the very least, wait a good half an hour after a run. (Then you avoid a false reading and over filling etc…)

Check the oil with the vehicle on a level area.

Change the oil regularly.

Use the correct grade of oil for your vehicle. ("Aha", you say. "You didn't mention that". Well, clever-clogs, that will be another article. ;) )
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