There have been perhaps 100s of threads on engine oils. If one searches other car forums (BMW, Chevy, etc) , one finds oil is a fairly common topic everywhere. Oil serves multiple functions (lubrication, cooling, minimize engine deposits etc), and lately I'd started to think again about the lube properties.
After reading a variety of articles, I'm of the opinion and judgement (not "proven fact" !) that the oil properties I was most interested in were:
1) cold & start-up lubrication.
2) adequate pressure when hot.
3) "adequate" Zinc (at least 0.10% , preferably around 0.12-0.14 %).
#1 especially, the ability of an oil to quickly provide lubrication during cold startup and until the engine is warmed up, seemed especially important to me, for a normal street-driven car.
I started reading through oil manufacturer's data sheets, and to keep track of it, compiled the key oil specs into an excel spreadsheet - Attached. I have about 2 dozen oils listed. if you don't have Excel, a free excel viewer can be downloaded from the Microsoft website.
One observation I made was that traditional SAE oil grades (5W-30, 20W-50, etc) are nearly useless for estimating cold and hot oil properties. I suspect SAE weight is a partly outmoded concept that persists simply because it provides easy-to-understand guidance to the typical consumer. I noticed there was usually negligible measured differences between the 5W30 & 10W30 grades.
Mfr's data sheets typically provide actual measured viscosity (in cS - centistokes) at 100ºC (212 F) and 40ºC (100 F). I found a calculator on the web that extrapolated viscosity to other temperatures, so I calculated viscosity at 20C (68 F) and 10C (50F) to provide guidance concerning colder startup.
Viscosity Index (VI) is an indication of how stable the oil properties are over the temperature range - higher is better. The synthetics have better VI than conventional dino oil.
Some amount of Zinc is important to reduce risk of wear under high-pressure metal-to-metal conditions. The flat tappet stock cams are one such risk area. A number for sufficient Zinc % is subject to debate, IMHO 0.1% is a bare minimum and 0.12-0.14% is more desireable.
The new ILSAC GF-4 oil spec mandates Phosphorus 0.06-0.08 wt%. Zinc is not spec'ed but is typically similar to Phos. Avoid these ILSAC GF-4 oils, unless you're adding additional Zinc (GM EOS).
But Oils that are not GF-4, do not necessarily have enough Zinc/Phos, either. Addition of GM Engine Oil Supplement may be indicated. 8oz (1/2 bottle) of EOS per 5 qt oil will increase Zinc/Phos by approx 0.03 %.
Oils that are ILSAC GF4 and thus to be avoided (unless EOS is added), includes all the Mobil 1 except for the 0W-40 grade. Somewhere I read an analysis of that grade, showing about 0.11-0.12% Zinc.
Royal Purple is a popular oil, but I didn't include it because Royal Purple doesn't publish any specs for their racing oils. RP doesn't list Zinc/Phos for their "consumer" oils. At least, Chevron, Valvoline, and to a lesser extent Mobil, are all very upfront.
So in summary, my ideal oil would provide:
1) low viscosity at 10C/50F, for better lube and protection on a cold engine.
2) "sufficient" oil pressure when warmed up. If I didnt have sufficient pressure, I'd install a pressure-booster plate, rather than compromise #1.
3) Zinc 0.12% - 0.14%.
The most intriguing and potentially "ideal" oil was the Chevron Delo synthetic 0W-30, but I can't find it anywhere!
Next up, Valvoline Not-Street-Legal Racing Synthetic , in 5W30 or 10W30.
The Mobil1 oils, with addition of 8-12 oz EOS, should also be very good (except 0W40 does have enough Zinc).
As mentioned, no Royal Purple is listed because they don't publish their specs.
The traditional 15W-40 diesel oils have very high cold viscosities (over 600 cS at 50ºF), so I don't think I'd use them in my gasoline cars.
After reading a variety of articles, I'm of the opinion and judgement (not "proven fact" !) that the oil properties I was most interested in were:
1) cold & start-up lubrication.
2) adequate pressure when hot.
3) "adequate" Zinc (at least 0.10% , preferably around 0.12-0.14 %).
#1 especially, the ability of an oil to quickly provide lubrication during cold startup and until the engine is warmed up, seemed especially important to me, for a normal street-driven car.
I started reading through oil manufacturer's data sheets, and to keep track of it, compiled the key oil specs into an excel spreadsheet - Attached. I have about 2 dozen oils listed. if you don't have Excel, a free excel viewer can be downloaded from the Microsoft website.
One observation I made was that traditional SAE oil grades (5W-30, 20W-50, etc) are nearly useless for estimating cold and hot oil properties. I suspect SAE weight is a partly outmoded concept that persists simply because it provides easy-to-understand guidance to the typical consumer. I noticed there was usually negligible measured differences between the 5W30 & 10W30 grades.
Mfr's data sheets typically provide actual measured viscosity (in cS - centistokes) at 100ºC (212 F) and 40ºC (100 F). I found a calculator on the web that extrapolated viscosity to other temperatures, so I calculated viscosity at 20C (68 F) and 10C (50F) to provide guidance concerning colder startup.
Viscosity Index (VI) is an indication of how stable the oil properties are over the temperature range - higher is better. The synthetics have better VI than conventional dino oil.
Some amount of Zinc is important to reduce risk of wear under high-pressure metal-to-metal conditions. The flat tappet stock cams are one such risk area. A number for sufficient Zinc % is subject to debate, IMHO 0.1% is a bare minimum and 0.12-0.14% is more desireable.
The new ILSAC GF-4 oil spec mandates Phosphorus 0.06-0.08 wt%. Zinc is not spec'ed but is typically similar to Phos. Avoid these ILSAC GF-4 oils, unless you're adding additional Zinc (GM EOS).
But Oils that are not GF-4, do not necessarily have enough Zinc/Phos, either. Addition of GM Engine Oil Supplement may be indicated. 8oz (1/2 bottle) of EOS per 5 qt oil will increase Zinc/Phos by approx 0.03 %.
Oils that are ILSAC GF4 and thus to be avoided (unless EOS is added), includes all the Mobil 1 except for the 0W-40 grade. Somewhere I read an analysis of that grade, showing about 0.11-0.12% Zinc.
Royal Purple is a popular oil, but I didn't include it because Royal Purple doesn't publish any specs for their racing oils. RP doesn't list Zinc/Phos for their "consumer" oils. At least, Chevron, Valvoline, and to a lesser extent Mobil, are all very upfront.
So in summary, my ideal oil would provide:
1) low viscosity at 10C/50F, for better lube and protection on a cold engine.
2) "sufficient" oil pressure when warmed up. If I didnt have sufficient pressure, I'd install a pressure-booster plate, rather than compromise #1.
3) Zinc 0.12% - 0.14%.
The most intriguing and potentially "ideal" oil was the Chevron Delo synthetic 0W-30, but I can't find it anywhere!
Next up, Valvoline Not-Street-Legal Racing Synthetic , in 5W30 or 10W30.
The Mobil1 oils, with addition of 8-12 oz EOS, should also be very good (except 0W40 does have enough Zinc).
As mentioned, no Royal Purple is listed because they don't publish their specs.
The traditional 15W-40 diesel oils have very high cold viscosities (over 600 cS at 50ºF), so I don't think I'd use them in my gasoline cars.
