Oils ain’t oils when it comes to diesel engines. Fully synthetic, low-ash oils are essential for vehicles fitted with DPFs and not everything with 5W-30 on the bottle is created equal.
Says Andrew Leimroth from Berrima Diesel: “From what I’m seeing, the crop of new-age common-rail diesels are coming in with problems far earlier in life than the older ones. I believe that there are more troubles to come from using super-thin oils in our generally hot weather rather than any benefits. The amount of engine blow-by seen in new diesels and the evergrowing need and use of oil catch cans says something…”
Frank Spiteri agrees oil is absolutely critical: “The wrong oil can block a DPF very quickly,” he says. “It is case sensitive. Nissan Navaras need different oil to BMWs. There’s a lot of 5W-30 stuff out there but put in the wrong one and it will blow black smoke. One customer was told he needed new injectors. We changed his oil and filter and his smoke problem disappeared. That saved him $2400!”
Penny pinching by service managers sometimes amounts to using ‘house’ oils, usually semi-synthetics but Spiteri Snr. warns it’s worth insisting on the right stuff and spending the extra $4 a litre on the fully synthetic recommended by the car maker.
The other critical factor is oil breakdown, which several experts suggest can begin as early as 7500km on modern diesel engines.
Many manufacturers, however, are promoting service intervals of 15,000km.
The independent experts who service the things have strong views that 10,000km service intervals are a much wiser long-term investment in engine health.