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Globe Drive (Joe Belanger/iStockphoto)
Globe Drive (Joe Belanger/iStockphoto)

Maintenance Do it yourself

The truth about oil changes for vintage cars Add to ...

Oil. When it comes time for a change, most of us just wheel into the nearest lube joint or dealership to get it done by someone else. The do-it-yourselfer who breaks out the tool kit, jacks up the front end, rolls up his or her sleeves and changes their own oil is becoming an endangered species.

And anyway, many of today’s cars are so precise in their lubrication requirements, it’s better to leave it to an expert in the first place. In some cases, you can void your warranty should you scramble the car’s computer by putting in the wrong engine oil.

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Not so the vintage/collector car owner. For most of us Luddites, do-it-yourself maintenance is a point of pride. If you’ve put years of blood, sweat and tears into your collectible, the last thing you want is for a stranger to lay their greasy hands all over your baby. For DIY-ers, changing oil at least twice a year is something of a ritual and most collector car buffs just do it as matter of course. Pick the best oil you can, change the filter while you’re at it, and Bob’s yer uncle.

So it came as something of a bombshell when rumours began circulating that oil manufacturers such as Castrol, Quaker State, Penzzoil and so on were marketing a lubricant that didn’t do the job when it came to old cars.

The problem was that one of the active ingredients in engine oil, zinc dialkyldithiophospate – or ZDDP, which has been around for at least half a century – was found to hasten the demise of catalytic converters in many automobiles. So oil manufacturers began to slowly reduce the ZDDP content in their products to the point where now, varieties such as Castrol GTX (a favourite with British car lovers) have almost none.

This may be good for the environment, but the downside is that ZDDP protects things like camshafts, piston rings, and lifters, and some restorers reported experiencing catastrophic engine failures after changing to oil with low ZDDP. The Internet was abuzz with horror stories, dire consequences, and tales of woe.

But like so many things on the web [ever tried to self-diagnose a medical condition on the Internet? Don’t] – there was more to this than meets the eye. Yes, lack of ZDDP could damage a freshly rebuilt or high-performance engine, but in nine cases out of 10, it made no difference whatsoever.

“It was all a gross oversimplification,” explains Chris Barker, technical services manager for Royal Purple, which manufactures lubricant products aimed at collectors and hobbyists. “It was nowhere near as bad as people made out, and there were other factors at work here as well.”

Barker says that a crop of bad engine components made off-shore didn’t help the hobby car community, and that compared to the oil that was being produced 50-60 years ago, today’s lubricant is light years ahead of what it used to be. Think about it: in the 1950s, for example, everybody used non-detergent 30-weight, and ZDDP didn’t even exist.

However, Barker concedes, “if you have a hot engine with a really aggressive cam and high-performance internals, you probably shouldn’t use oil that you buy at your local Walmart. These kinds of engines should be using an oil specifically designed for racing.”

The same is true of freshly rebuilt engines. For the first few thousand kilometres, during the break-in period, a high-performance oil with zinc and phosphorous content should be used. Royal Purple makes such a product, as do other manufacturers such as Valvoline, Duckham’s, Kendall, Mobil 1, and on and on.

How to tell if the oil you’re purchasing has ZDDP in it? On the back of the container, you should find a small circle with the weight of the oil and an American Petroleum Institute [API] service rating within it. If the oil is rated “SM” or “SN,” it will likely have a low ZDDP content. For any car with a catalytic converter, this presents no problem. For oldsters, you should be okay as well, as long as the car has a few kilometres on it. What you’re looking for is an API rating of SL or SJ or lower – if you can find one.

You can also buy ZDDP additives that you can add to the oil when you change it; AC Delco, for example, makes one. Chris Barker, however, recommends against that. “Today’s oil is made to a precise formula, and if you fool around with it, you can change the oil’s effectiveness.”

So the moral of the story: by all means, change your own oil, but don’t believe everything you read on the Internet.

Send your automotive maintenance and repair questions to globedrive@globeandmail.com

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