New cars come with maintenance schedules that give you time/mileage intervals for things like oil changes, tune-ups, tire rotation and so on. Follow these recommendations and – assuming a decent/sound car to start with – it ought to be a long-lived car.
But what about old, semi-retired cars?
They came with maintenance schedules, too. But these assumed regular use. When that assumption no longer applies . . . what to do?
For example, my 1976 Trans-Am. I still have all the original paperwork, including the service schedule. It tells me to change the oil once every 7,500 miles or six months – whichever comes first. Well, it’ll take me at least a decade to rack up 7,500 miles – since the car only leaves the garage occasionally. I drive it about 500 miles each year.
I should probably change the oil more often than once every ten years.
But once every six months? Given maybe 250 miles or so of driving? That seems . . . wasteful.
Expensive, too. Oil – the good stuff – costs more than $10/quart and the old Pontiac takes six. Plus a filter. Plus tax – and it’s about $75 to change the oil . . . myself.
But the oil does need to be changed at some point. So – what point? I split the difference and do it once a year, regardless of the mileage. Even if the car has barely been driven at all.
In fact, precisely for that reason.
Not because the oil wears out. Oil is pretty much eternal, actually. But it does become diluted and contaminated, especially if it’s sitting in the crankcase of an old car with a carburetor perched on top. These invariably leak gas, which finds its way into the crankcase, where it dilutes the oil. And gas is not a lubricant. It is a solvent. This is not what you want mixed in with your lubricating oil.
There is also condensation – water – that mixes with the oil. Also not a lubricant. And, sludge – the bane of lightly/rarely-used cars. It can gum up the works, including the oil pump pick-up, which is usually located in the bottom of the oil pan. If the intake screen gets glutted up with the internal combustion equivalent of chunks of cholesterol . . . well, the results are actually kind of the same.
Which is why I change the TA’s oil once a year, no matter how few miles it’s been since the last oil change. I take it for a half-hour drive first, too. In order to thoroughly warm the engine so that the hot oil carries with it as much stuff-I-don’t-want in the crankcase out with it as possible when the drain plug is removed.
And I use synthetic oil (Amsoil, usually) because of the superior protection it provides, especially in a car that sometimes sits for weeks at a time. Synthetics stand up better to that kind of duty, in particular, the thin lubricating (and protective) film on critical wear surfaces such as bearings, cylinder walls and camshaft lobes.
Speaking of which . . .
If you own a car like my TA that has an engine with a flat tappet camshaft (as opposed to a roller camshaft) you should use an oil with the anti-wear additives – manganese and zinc – these engines require, but which have been eliminated from almost all over-the-counter engine oil, including the high-end synthetics.
This doesn’t mean they are not high-quality and using them in modern engines is no problem. But if you have an older engine with a flat tappet camshaft (generally speaking, this is American-brand stuff made before the early 1980s) then you should either buy an oil that has the additives (I use Amsoil’s Z-rod 10W30 in the TA) or buy a bottle of additive (GM sells it over the counter at dealers; there are other sources, too) and . . . add it to the oil at each changeout.