Expensive engine oil doesn’t cost you, it pays you

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The Race Group At least that's the firmly-held view of Brian Utton, heavy duty technical manager at Castrol. Here’s his justification for the contentious assertion.

In these cash-strapped times, many truck fleet engineers (not least in local authorities) are increasingly faced with conflicting pressures. They are expected to cut running costs on the one hand, but on the other to extend the lives of vehicles that normally would be ripe for replacement.

Vehicles once covered by manufacturers’ repair-and-maintenance agreements are now out of contract and not being replaced as planned but asked to soldier on for another year or so. But it remains the fleet engineer’s job to keep them running reliably. With the cost of diesel fuel scaling new peaks with every passing week, it is hardly surprising that the pressure to improve fuel economy is intensifying as well. So what is a fleet engineer to do? My advice in many instances is to make what may well seem like an odd decision: switch to a more expensive engine oil. To be more precise: one that is expensive in terms of cost per litre. The point is that the impact of oil type on lubricant cost per kilometre and, ultimately, on overall cost per kilometre of vehicle operation is far more significant in the long run. So, what is the best buy when it comes to filling the 40- litre sump of a typical long-haul truck? Is it a standard mineral oil at around £2.25 per litre, a synthetic at £2.90, or an allsinging, all-dancing lowviscosity, high-performance oil at maybe £5.90 per litre?

For the sake or argument, let’s consider two representative oils from the Castrol range, both of the low-SAPS (sulphated ash, phosphorus, sulphur) variety: Enduron low-SAPS 10W-40 and Elixion low-SAPS 5W-30; and compare them with what we’ll call a bog-standard mineral multigrade. As always pointed out in the excellent annual Commercial Vehicle Engineer analysis of truck operating costs, bear in mind that the actual prices you will pay for these oils will vary considerably, not least with size of order. But for the sake of argument again, we’ll stick with the per-litre prices of £2.25, £2.90 and £5.90.

The first thing that needs to be established with any engine oil is its suitability for the particular truck in question, taking into account make, model, age and vehicle operation. Truck-makers have their own individual standards on wear-protection of lubricants and their ability to cope with contaminants. These standards should be used in conjunction with oils’ E-numbers to decide suitability. Some people still mistakenly think an E4 oil must be suitable for a Euro-4 engine. Sadly, the truth is far more complex. The Enumbers on engine oils represent classifications ("sequences” in the technical jargon) published by ACEA (Association desConstructeurs Europeéns d’Automobiles), the Brussels-based association representing European vehicle manufacturers. Thesesequences are based loosely on Mercedes performance specifications, but tailored to meet various engine requirements.

They are used by engine manufacturers and oil companies alike as a measure of compatibility. Beware of some anomalies. The performance of E5 oils, for example, is inferior to that of E4s but superior to E3s, so perhaps really should have been categorised as E3.5. But the crucial thing is to ensure that the engine oil you intend to use meets the requirements specified by the truck manufacturer and is suitable for the truck’s  particular operation.

This brings us to our first money-saving opportunity. Some vehicle manufacturers approve more than one grade of oil, but the specified oilchange intervals vary with grades. Take for instance a truck with a standard recommended oil-change interval of 100,000km. This is extended to 150,000km with upgraded oil. Let’s do the maths.

The cost of 40 litres of mineral oil (E7) changed at 100,000km is £90 (40 x £2.25). So the cost of oil per 10,000km is £9.00. The cost of 40 litres of Enduron low-SAPS 10W-40 (E4, E6, E7) would be £116 (40 x £2.90) but its oil-change interval is 150,000km, so the oil cost per 10,000km is £7.73. In other words, oil costs have been cut by 14 per cent. And the savings do not end there, because other oil-change costs ought to be factored in, including labour, waste-oil disposal, filters and gaskets, not to mention lost productivity while a truck is off the road. In 300,000km a truck on standard mineral oil would have needed three oil changes whereas on Enduron low-SAPS 10W-40 it would have needed only two.

On top of all this, the higher-quality oil will have provided better protection against engine wear, even with the longer oil-change interval. And for a truck with a diesel particulate filter (DPF) the low-SAPS properties of the more expensive oil will have meant less risk of filter clogging and the attendant adverse effects on vehicle performance or perhaps even costly filter replacement.

Now let’s consider Elixion low-SAPS 5W-30. It seems difficult, on the face of it, to make a strong case for this oil. Like Enduron low- SAPS 10W-40, it conforms to E4, E6 and E7 standards yet is much more costly. An oil change on our long-haul truck would cost £236 (40 x £5.90), so the oil cost per 10,000km would be more than doubled, as the oil-change interval would be no greater than with the Enduron oil. But independent field tests have confirmed that switching from a 10W-40 engine oil to a 5W-30 can deliver fuel consumption savings of four per cent. The saving is greatest in winter, at low ambient temperatures, so a year-round average saving of three per cent would be a reasonable assumption.

Let’s factor this into the truck’s combined fuel and oil costs, assuming the truck’s average fuel economy is 8mpg. So over 150,000km (93,205 miles) this truck will consume 52,425 litres (11,650 gallons) of fuel. At an assumed bulk diesel price (excluding vat) of 109p per litre, that comes to £57,143. A three per cent fuel saving would cut this bill to £55,429. So switching to Elixion low-SAPS 5W-30 would cost an additional £120 but should deliver a fuel saving worth £1,714 over 150,000km. Suddenly the Elixion case seems anything but weak.

It is hard to think of any other investment of such modest size that is capable of delivering a saving like this in a transport operation. Even if the oil did not perform nearly as well as expected and returned only a one per cent fuel saving, well over £500 still would be knocked off our truck’s fuel bill. And it is worth underlining that these savings would be consistent, and not dependent on driver training or behaviour, or on anyone remembering to do something or use special equipment.

Castrol is now so confident in data from field and laboratory tests that we are offering a software-based fuel efficiency calculator to allow operators to work out fuel savings predicted to result from switching to Elixion low-SAPS 5W-30.

For more information go to www.castrol.com/ukbusiness (in the UK) or www.castrol.com/iebusiness (in the Irish Republic). 

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