In Issue 57, Dave Landers took a look at oils and their suitability for your vintage or classic
vehicle (CMM, December '93).
WHICH OIL FOR YOUR CLASSIC?
CLASSIC OWNERS ARE sometimes unsure about which oil is best for their vehicle - and understandably so.
There are so many different types now on the market that it's pretty confusing - and if you believe the adverts, each one is better than the next! One way out of the puzzle is to buy a modern oil that's been specially blended for vintage and classic vehicles - like Penrite.
However, a recent letter to CMM made the point that these new 'classic' oils tend to be expensive, yet the original monograde oils (as recommended in 1950s handbooks) can still be found at very reasonable prices. Mr Morgan, who wrote the letter, mentioned that he uses a non-detergent SAE30, made by Newton Oils, in his 1954 Austin Somerset.
In fact, Newton are just one of several firms up and down the country who can still supply engine oils that match the original specification for an Austin A40... and a Morris 8, a Ford Pilot, an MG TC, or whatever. But is it a good idea to ignore recent advances in lubricant technology? Are you doing the right thing for your engine by deliberately seeking out an old-fashioned oil?
In effect, by rejecting modern oil, important extra features are also being rejected - like anti-wear agents, corrosion inhibitors, emulsifiers (which soak up condensation), and anti-oxidants that stop the oil burning and thickening. More obviously though (as Mr Morgan made clear by describing his preferred oil as "non-detergent SAE30"), a traditional oil won't keep the insides of the engine clean - nor will it be a multigrade suitable for both summer and winter use.
The benefits of using a more modern oil can be summed up in one word: 'additives'. Not the accessory-shop stuff that comes in little ring-pull cans, but the chemicals which are already included in the oil by the blenders. A modern oil, in fact, can be composed of up to 20% additives.
Okay, but who needs them? Surely - you might ask - if a straight SAE30 was good enough for the car when it was built, why not use it today? After all, that's what the engine was intended to use, wasn't it?
True... but the first thing to remember is that back in the early fifties owners had to carry out much more engine maintenance - and they didn't get the sort of service life which we now take for granted. Looking after your car in those days didn't just mean polishing it. It meant cleaning out the sump and decoking the head at regular intervals.
Continual tappet adjustment to take up wear on the cam followers. Oil control rings needed at 30,000 miles - and probably a rebore and a crank grind at 50,000. The fact that we get troublefree motoring from those same engines today (and rarely need to look inside them) is mainly due to better lubrication.
Multigrade detergent oils got a bad name when they first appeared because, frankly, they weren't very good. At 10W/30 viscosity, they were really too thin for the engines of the day - and they got even thinner under load. The additives which were used forty years ago simply weren't strong enough, and it was soon found that a 10W/30 oil wasn't an acceptable substitute for a 30 monograde.
A spell of fast motoring in hot weather and the oil film broke down - resulting in a seized engine. The oil companies had also overlooked the fact that their new detergent additives would scour accumulated carbon deposits from dirty, high mileage engines - causing disastrous blockages and yet more engine seizures.
By the end of the fifties, though, when the Mini appeared, multigrades had improved vastly. Lessons had been learned, and the later 20W/50 oils were even able to cope with the Mini's gear wheels thrashing around in the sump.
Technology doesn't stand still, of course. Car engines keep changing, and the oil companies have to develop new products to keep pace. The trend nowadays is towards fuel-efficient, low emission engines. Built to tight tolerances, they have small sump capacities so the oil gets up to temperature very quickly. Today's premium synthetic oils are designed for today's cars. They're technically brilliant - but, unfortunately, they're too thin and too highly detergent for older engines.
So what should we do? Use Penrite, or go back to the old monogrades?
For most people, there's an easier option. As far as post-war classics are concerned, good quality 20W/50 is the best choice. At normal operating temperature it's similar in viscosity to an SAE30, but it will circulate more quickly from cold and generally give better protection. 20W/50 used to be universally recommended not so long ago, and the big name firms still produce it - the only difference being that the pack is now often marked 'suitable for worn engines'.
Shell 'Four Seasons', for example, is today marketed as an economy oil - in other words, you wouldn't want to pour it into a Ford Cosworth. But it's still the same high quality it always was, and perfect for classics - not too detergent, though containing enough additives to safeguard your engine.
There are cases where a traditional monograde will be better, though.
Vintage high-performance engines were usually designed to take a really thick oil - because when they were built the only way that reliability could be guaranteed was by specifying SAE50 or 60 grade oil. So these motors were engineered with clearances that are too wide for ordinary multigrade, and they need that old SAE50 or something at least as thick.
Now, here's where Penrite's 'classic' oils really come into their own. Penrite blend special multigrades which are heavier than 20W/50 - their HPR series oils are designed to take up those wide clearances, yet also offer all the extra protection of modern additives.
However, monograde oils don't necessarily have to be 'additive-free'. Silkolene is an old-established firm currently making a range of monogrades that are mildly detergent, with anti-wear additives.
There's no advantage to be gained by turning back the clock to a time when sumps got gungy and heads got covered in carbon. A medium detergency oil, changed regularly, helps to stop these deposits forming - and any engine that's been run on readily available oil over the last thirty years has been using detergents.
A final word of warning, though. If you've been using a non-detergent monograde, don't change to detergent oil without first stripping and cleaning the engine. There's a real risk of blockages and bearing failure occurring otherwise.
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