Oil for Lister HA2

[bargee1759]

Not true.

 

 

Mineral Oils are graded by SAE according to their measured viscosity at 100 C. Higher numbers mean higher viscosities. The range runs from 0 to 60. Mineral Oil viscosity decreases as the temperature rises so any SAE xx oil is less viscous (thinner) at 100 C than it is at room temperature and thicker at 0 C than it is at room temperature. This is inconvenient because hot, thinner oil may not cut the lubricating mustard in a highly loaded engine . So the oil industry invented multi-grade oils. These behave a bit like two different oils and are given two designations SAE 20W/50

 

The W in an SAE oil designation refers to its viscosity at a cold temperature (usually 0 C.) So an SAE 20W/50 has the same viscosity at 0 C as an SAE 20 oil would have at that temperature and the same viscosity as a 50 grade oil would have at 100C. This is achieved by adding viscosity Index improvers.

 

"Straight" oil is mineral oil with no additives. Rare as rocking horse poo these days. The term is often used wrongly to describe single grade oils. Single grade oils have no viscosity index improvers but they do have a whole cocktail additives ranging through anti- wear additives, anti oxidants, detergents, anti-foaming additives and so on, depending on the market requirement and the ingenuity of the oil chemist.. The same additives can be found in multi-grade oils.

 

The purpose of detergents is to keep the internal parts of the engine as clear of sludge as possible by holding the sludge in suspension in the oil. The expectation is that the oil filter will the catch the suspended sludge and the oil can go round again and collect some more. Where filtration is poor, or non-existent, as in many old designs of marine engine detergent oils are a bad thing as the sludge suspension is abrasive and accelerates the wear on bearings and other sliding surfaces. Old engines therefore need low detergent oil so that the sludge can fall out of the oil in the sump or oil tank for dry-sump engines. To give the oil enough time to settle out the sludge old/low filtration engines tend to have larger oil capacities than is strictly necessary for lubrication or cooling purposes.

 

I know a little about aircraft piston engines, and suspect that the single grade oil in the OP's example was simply one which contained less anti-wear additives and more of the specialist ones which promote running-in. Once run-in a multi-grade would then be used to ease cold-starting. Most oil companies produced a running-in oil and once upon a time new cars were delivered filled with one of them. This went out of fashion once manufacturing could produce surface finishes and finish tolerances that were similar to those of a run-in engine.

 

 

Synthetic oils are something completely other.

 

 

N

Yes you are right BEngo, I mislead! You quote straight from SEA J300 & I was thinking of the single grade ashless dispersant aviation piston oils where the "W" is a dfferent thing & I should have said additives not detergents too. (just to add more confusion W100 aviation oil is SAE50!) I'd already been up 19 hours when I posted that so next time I'll get my facts straight first. I'm going to sit in the corner now with a hat on sporting a large "D" on it.

[bizzard]

Yes you are right BEngo, I mislead! You quote straight from SEA J300 & I was thinking of the single grade ashless dispersant aviation piston oils where the "W" is a dfferent thing & I should have said additives not detergents too. (just to add more confusion W100 aviation oil is SAE50!) I'd already been up 19 hours when I posted that so next time I'll get my facts straight first. I'm going to sit in the corner now with a hat on sporting a large "D" on it.

19 hrs plus!!How long did you stay up ? That aeroplane must have had mighty big fuel tanks.