A place for things that don't fit into the automotive world

Engine Oils & Other Fluids Facts & Myths & Alternative Truths

More
5 years 1 month ago - 5 years 1 month ago #26688 by Andy.MacFadyen
I am starting this topic to clear some of the confusion and misunderstanding surrounding oils and oil change intervals. I will start explaining the traditional oil SAE grade system, Mineral Oils and how Synthetic oils differ from them, the basic of Syntheic oils and what a semi-synthetic label may or may not mean.

Watch this space ........

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



Last edit: 5 years 1 month ago by Andy.MacFadyen.
The following user(s) said Thank You: Noah, Chad

Please Log in or Create an account to join the conversation.

More
5 years 1 month ago - 5 years 1 month ago #26740 by Andy.MacFadyen
Lets start 100 years ago, in those days engine lubrication and lubricants were almost unrecognizable from what they are today, although by this time most engines had engine driven oil pumps \the connecting rod big end bearings still relied for lubrication on scooping up oil from troughs in the crankase, this system is still in use in some Briggs & Stratton lawnmower engines. The bearings themselves were very different not the modern shell bearings that have been universal ever since the 1930s but were cast in place by pouring a molten low melting point alloy “Babbit Metal” into recesses in the connecting rods and cylinder block. When cooled the bearing surface was custom fitted using hand scrappers to suit the journal diameters.

Babbit Metal Wikipedia

Link to Hemmings Dailly site Pouring Babbit Big End Bearing

Oil filters only became common fitment in the early 1930s but were not the full flow filters we know today but by-pass “oil cleaners”. Some oil would be continuous tapped off the main gallery then passed through through a small bore pipe to the oil filter and returned directly to the oil pan.

Wikipedia Oil Filters

Just prior to WW2 what we would recognise as modern engine lubrication system a pressure fed crankshaft with shell bearings a full flow oil filter and a pressure relief became the norm.
Oil change intervals were less than 3,000miles .

The oils used were also unsophisticated distilled from crude oil with no additives and much darker I appearance than modern oil. These were mono grade oils too viscous (thick) at low temperatures and thin at high temperatures. It was noticed that oils made from crude oil that came from the Gulf of Mexico made the best motor oils as they had what we now call multi-grade properties they flowed better at low temperatures but retained a higher viscosity at higher temperatures, for this reason US lubricating oil companies earned a reputation for a superior product. This also applies to mineral oils made from other undersea sources such as the North Sea.

Obvious the viscosity/thickness/weight of the has a major effect on how well the oil will protects the engine at low and high temperatures. For the reason the SAE introduced a grade scale.

The original SAE grade number 20, 30, 40 & 50 were based on the viscosity at 100c/212f these are grade numbers not viscosity units. Within the last two years because manufacturers are attempting to improve fuel economy and emission by using thinner oils a new grade number was introduced SAE 16. Single grade oils were still common through to the early 1960’s I can still remember our family business stocking SAE 30 and SAE 40.

Because vehicles must operate from a cold in low temperatures the SAE introduce an additional winter grade system 0W, 5W, 10w, 15w & 20w. The winter grade of the oil is measured by a very different method from the high temperature grade number, it is based on the lowest temperature the oil will flow through an orifice this gives a pretty good indication of how well the engine can pump the oil through the engine when cold.

" We're trying to plug a hole in the universe, what are you doing ?. "
(Walter Bishop Fringe TV show)



Last edit: 5 years 1 month ago by Andy.MacFadyen.

Please Log in or Create an account to join the conversation.

Time to create page: 0.239 seconds