June 29, 2016 Vol. 13 No. 13

Back in the day — and I mean baaaack — just about every cheap car I owned as a teenager had an engine that suffered from low oil pressure for one reason or another, or maybe the snickety-snick of bad connecting-rod bearings. Maybe both. Very annoying.

Apart from tearing the thing down and doing a rebuild, which I tried once as a 15-year-old– in the parental basement, where I failed comprehensively — there were two possible solutions: one, find a donor wreck and do an engine swap; or two, pour can upon can of thick oil into the sump. For me, like many of my friends, the second option worked best and the oil of choice was a super-thick additive called STP.

And it worked. A couple of cans of that treacle-like substance and the noises went away while the pressure-gauge needle went up. For a while.

Felon that I was, I’ll admit that I used that treatment once or twice in selling a car. A practice that goes on today, I have no doubt.

Anyway, all of that contributed to the idea that ‘thick’ — known as high viscosity –is good when it comes to engine lubes. A nearly universal idea, I’d guess, at least for the summer months when heat thins out an oil. I should think that many truck owners have subscribed to this theory and it’s likely that many still do.

A higher-viscosity lube does a better job of protecting an engine, just like it did in masking the issues with my own old engines, no?

Well, there may be some logic in there still, in some applications, but the new ‘Confidence Report: Low-Viscosity Engine Lubricants’ by the North American Council for Freight Efficiency (NACFE) suggests that with modern lubes less viscosity does not bring a reduction in engine protection. Better yet, it can deliver a significant gain in fuel economy in the 1% range, plus or minus a bit.

“In engineering terms,” the report explains, “viscosity is defined as a measure of a fluid’s internal resistance to flow. In a truck’s engine, mechanical losses from pumping and friction consume approximately 16% of the total energy input to a vehicle. Lower-viscosity oil will reduce those engine mechanical losses, thereby reducing fuel use.”

MISPERCEPTIONS MAY HAVE hindered the wide-scale adoption of lower-viscosity oils thus far, says the report, namely that belief that heavier oil increases engine durability. But, says NACFE, modern engines subject oil to a variety of temperature and lubricating conditions, and the ability of the engine oil to perform under these conditions depends on many more factors than simply its viscosity.

 Given the importance and the complexity of an engine oil’s performance and function, approval and release of new oils into the market is not taken lightly.