Thursday, December 6th, 2018


At the end of my last article, I promised you that I would try to make sense of the new “skinny” motor oils.  Their pros and cons and how they can make today’s vehicles run better and more efficiently.

Just a mere fifty or sixty years ago, when many of us were starting our driving careers, the mainstay lubricant for the era’s engines was a straight weight SAE 30 or 40 weight motor oil, or viscosity if you will. Viscosity refers to how smoothly oil flows at a specific temperature range.  If you lived up in the snow belt, around Michigan, Wisconsin or Wyoming, it was common practice to use the heavier oil during the two week summer season (just a little Florida humor) and then drop down to the lighter weight oils in the fall and winter. That was mainly so that the starters could turn the engines over in the frigid weather.  Block heaters patented in the late 1940s became popular in the fifties and are still used to this day.

Throughout the sixties, seventies, and most of the eighties, multi-weight oils became the norm.  These grades always had two numbers on the label with a “W” in between them.  That “W” stands for winter grade.  The flow rate at 0 degrees Celsius is 32 degrees Fahrenheit, for all you non-Canadians. Conversely, the higher number is rated at 100 degrees Celsius, which is 212 degrees Fahrenheit.  

The most confusing part of this is how can oil be thinner at lower temperatures and then thicken up at higher temperatures when the fundamental physics states that this is impossible.  What is happening is that the base oil structure is of a lower viscosity so that these engines can turn over in the winter, due to additives and some profound chemistry they can lubricate and protect these engines at higher temperatures and viscosity ranges demands.  

So that quart of 10w40 pours like a 10-weight oil but protects like a 40-weight oil.  Cool, end of the story, right?  That would be too easy!

First, enter General Motors, that stated that 10w40 should not be used in any of their vehicles as they felt that the standard of additives was too hard to guaranty that the oil would be as useful for longer drive intervals, because we ALL know that everyone always changes their oil every 3000 miles or 90 days.  10W30 became the standard for a long time until Ford Motor Company decided that only 5w30 should be used in their engines.

Not to be outdone enter the Federal Government and C.A.F.E., otherwise known as the corporate average fuel economy standards.  Which states the “if you want to sell cars in the US, and not be heavily penalized your corporate fuel economy must be?  The number for an average mid-sized car in the year 2018 according to C.A.F.E.should be about 34 mpg.

How is that being accomplished?  Here’s how smaller and lighter vehicles, aluminum and plastic bodies, smaller and more efficient engines that have even tighter tolerances that DEMAND skinny oil, we’re talking 0 weights — variable valve timing which is running on the assumption that the proper weight oils are being used and serviced with the proper filters during the appropriate intervals.  Externally mounted performance enhancers (turbochargers) which depend on adequate oil services and intervals, as well as instructions on how to spool down, said turbos so that they don’t deconstruct themselves just out of the warranty periods. ( I bet the car salesman didn’t tell you that when he sold you that V6 truck that pulled like an eight-cylinder because  of the two extra turbos hanging on the side of the block).

The moral of this story is to read your owner’s manual, find out which weight oil you’ll need, use the best oil filter that you can buy and follow all of the SEVERE MAINTENANCE schedules. In the long run, it will keep more money in your pocket and out of mine, because you will use less fuel, protect the inner working of the engine by not replacing turbos, variable valve timing solenoids, and cam driven fuel pumps that are just outside of the warranty period.