How to change engine oil like a pro

My regular mechanic strongly advised me against changing the engine oil myself, explaining that the job requires a professional since the engine could be easily damaged. Is this true?

Sam(antha)

Changing engine oil is one of the more basic service routines, and does not require specialist knowledge or skills. But it does need to be done properly. And often it is not, even by “professional” workshops. The irony is that many amateurs do the job with enough competence and more diligence. And yes, doing it wrong can cause engine damage, ranging from barely perceptible to serious depending on what mistake is made. Here is a guide to the possibilities. The oil should be drained when the engine is hot, when all the particulates in the oil and sump are stirred up and suspended in the fluid. That way, when the drain plug is removed, the oil will be hot and runny and flow out faster, taking more of the detritus with it. To maximise the flushing power of the outflow, the filler cap should be opened before the drain plug is removed, while the plug should be left open until the last drop.

The old oil should be captured for eco repurposing or safe disposal. When the engine is cold, the oil will thicken and some particulates will settle in the sump. The flushing rate will be slower, leaving particulates behind, even more so if the filler cap is still on.

The right tools, the right torque

The drain plug should be removed using the correct tool, preferably not a hammer and chisel. The integrity of its brass washer should be checked, and the plug thread and tip should be carefully wiped (it is magnetic, to “catch” particles of steel sloughed by the engine). Both parts should be placed on a clean surface, not on a dusty/sandy floor, while the plug should be tightened (using the right tool) to the correct and quite high torque. Too little might allow it to leak or work loose over time; too much might damage the washer and the threads of both the plug and the sump fitting and require a hammer and chisel at the next change, and eventual stripping.

Removing the old oil filter will require a specialised tool or a home-made strap or webbing/rope…or very strong wrists. It is often in a hard-to-reach place. The new filter should be an “original” part or the highest-quality alternative you can find or afford. Before fitting, it should be half filled with the new engine oil you plan to use to ensure the oil is circulated immediately the engine is re-started. The rubber seal and thread should be wiped with the new oil for a smooth refit. The new filter needs to be refitted straight and to the right torque (less than the drain plug but enough to prevent any leak or loosening in use). Wipe the external area of the filter and plug clean.

The new oil should be an appropriate grade and weight, with a sealed lid, and in the correct quantity. The oil capacity will be marked in the vehicle’s handbook, otherwise, the amount of oil drained out can be measured as a guide. On most cars, it will be between four and six litres.

The filler cap should be securely refitted and the engine started and idled for a minute or so and then moderately revved. Listen for any unusual sound. Turn the engine off and wait for a couple of minutes before checking the oil level on the dipstick, meanwhile, check under the car for any signs of a leak from the previously wiped-clean filter or drain plug.

Their equipment, your diligence

Knowing yourself, and your garage, which of you is more likely to do it all right or get something wrong? There is a third option though, save yourself the trouble and mess by using a mechanic in a workshop or petrol station grease pit – one will charge you for lubricants and labour with an overheads/business margin, the other will only charge you for lubricants (which have a margin built-in). Insist on watching the process yourself. Another advantage of this option is that an oil change is usually combined with greasing, and the pros are more likely to have a high-pressure grease gun than you are. Here, the proper procedure is not just to add new grease, it is to remove old grease.

In the pit (not in your Sunday bests) you can personally confirm that is done. Two birds with one stone, no sweat, and peace of mind that your car has been serviced properly. A few minutes in a pit also gives you a rare chance to check the condition of other components under the floor, including the inside walls of your tyres. Mechanics should do that automatically and thoroughly. Do they?

Salesmen are often poor advisors, pay more attention to the competitor

Gavin,

Is leasing the best way to buy a car?

Moses.

There are five ways to get the things you want. Make them, steal them, barter them, pay cash or get credit. Those are life's deals. There are no others. There is always a price to pay, the only option is in how (and when) you choose to pay it.

This has been the case since Adam whittled woman out of a rib (make it), since club-wielding cave-man invented matrimony with violence (steal it), since JJ Hughes swapped Model T Fords for wheat crops in Uasin Gishu (barter), since the clink of the first cowrie shell in Gedi (cash), and since Dr Faust went on tick with Old Nick (credit).

'Course, lawyers, accountants and salesmen have invented hundreds of different words to describe each of these processes in an attempt to bewilder, beguile and finally bedevil and behoove the benighted public to bethink them beneficent and by these parts to ensure the party of the second part has to pay the party of the first part such a huge part of his last part he's got nothing left to part or party with. The business of usury - so famously championed by Shakespear's trader of East Mediterranean extraction in an Italian town with wet streets - has been euphemised, bastardised, legalised and otherwise disguised by all manner of pecuniary poetry.

Call it what you like. Credit is credit. A get-now-pay-later system. And pay later must, by definition, mean pay more to finance the cost and the profit of a credit facility. There are dozens of "new" schemes on the Kenya market. None of them re-invent the credit wheel, but they all spin it in different ways. While the options proliferate and evolve, I offer no judgment, but here are a few principles to be going on with.

One: You are out there to buy a car, not a fancy finance scheme or bonus extras. So above all, select the vehicle first, on the vehicle's merits.

Two: When you have chosen the right vehicle for your purposes, only then look at your different options for paying for it. Salesmen are often poor advisors - competitors make better research assistants.

Three: Whatever the sales pitch calls it, if you don't pay in-full and up-front, you are on a credit scheme. You are therefore buying not only the car, but also the money with which to pay for it. Evaluate both purchases, separately, with equal care.

Four: There are some very good deals out there, but any deal that looks too good to be true, probably is. Caveat Emptor (Let the Buyer Beware) is not just a legal principle. It is good advice. Finally, if it has anything to do with motoring (or any commercial transaction, for that matter) mistrust the word "Free".

Why the odd engine rhythm when trucks are idling?

Hello,

Why do truck engines have a rhythmic thrum when idling (instead of a constant note) as if somebody is gently pressing the accelerator after every second?

Justus

To the best of my limited knowledge, this is known as a “hit-and-miss cycle”. Idling speeds must be high enough that the energy stored in the flywheel is enough to compress fuel to “fire” the next cycle. On small cars with light flywheels, that requires about 700-900 revs. Trucks have much heavier flywheels that store more energy, so low idling speeds are enough for the next “firing” – even two more, so when the revs are getting too low, the engine fires (hits) and when revs are already enough for the next cycle, it misses. Brrm, hush, brrum, hush, brrm, hush….on alternate seconds. Or something like that.

Getting more power out of smaller engines

Gavin,

When it comes to cars, what does the maxim “there is no replacement for displacement” mean? Is it a useful principle we should try to understand?

Douglas.

Not anymore. It belongs in the same bin as the saying “a photograph never lies”, which has long since been upstaged by computer technology such as Photoshop and CGI. “Displacement” is the techy term for what we all know as the “cubic capacity” (cc) of an engine; its “size”, the volume of air-fuel mixture each cylinder can suck in on its induction stroke, multiplied by the number of cylinders. Clearly, all other things being equal, the more air-fuel the engine can suck in, compress and ignite the more power the engine can produce. So, if you need more power, you want a bigger engine. But all other things are not equal. Advances in design technology and materials and especially in rev limits mean today’s “standard” 2-litre engines have more get-up-and-go than a 5-litre V8 could muster when that maxim was meaningful. The relationship between cc and power depends on all sorts of design elements other than total displacement, including bore and stroke ratios, piston numbers and weights, rev limits, combustion chamber shapes, porting precision, forced induction, ignition systems, the number of valves, the degree of camshaft lift, the number of cylinders, the crossing points and peaks of torque and horsepower curves, computerised engine management, flywheel weights and balances… What big straight sixes and V8s do still usually have more of is torque…which maxes at lower revs and offers potentially longer lifespans. Also, power (and economy) are not the only attributes engine designers and users seek. Smoothness, lazy grace and even the sound they make are sought-after characteristics, especially in large countries such as the US, with many very long, straight and almost traffic free roads. Smaller engines could maintain the speed but work harder (and noisily) to do so. Huge engines just burble, and are less tiring to live with.

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