Amazon has
5-Quart Castrol Edge High Mileage Advanced Full Synthetic Motor Oil (0W-20) for $22.32 - 5% when you check out via Subscribe & Save =
$21.20.
Shipping is free w/ Prime or on $35+ orders.
Thanks to Community Member
SUCHaDEAL for finding this deal.
About this item:
- Phosphorus Replacement Technology to help extend the life of the emission system
- Reduces leaks, oil burnoff and power robbing deposits
- 15,000 miles between oil changes*
- Meets or exceeds the following specifications: API SP/SN PLUS/SN/SM | ILSAC GF-6 | Meets engine test requirements of Chrysler MS 6395 | Meets Ford WSS-M2C947-B1 | Meets Ford WSS-M2C962-A2
- *Or one year, whichever comes first
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Top Comments
That all goes back to a famous lawsuit between Mobil and Castrol in the 1990s (yes, that Castrol).
Base oils are traditionally classified into five groups. Groups I, II, and III are derived from conventional crude oil. Groups IV and V are what were originally considered real synthetics — chemically engineered hydrocarbons like PAO, esters, polyglycols, or silicone. Mobil pioneered much of this technology.
For a long time, only Group IV and V oils could legally be labeled "synthetic," and they commanded a premium because they retained their physical properties far better.
In the 1990s, Castrol started using highly processed Group III base oils and marketing them as synthetic. Mobil sued, arguing that Group III was still conventional oil. Mobil lost. Castrol's argument was that Group III oils are so heavily processed that calling them synthetic was justified.
Fast forward to today: in the U.S. (but not in places like Germany or Japan), "synthetic" can legally mean Group III, IV, or V. So "100% synthetic" can be 100% Group III — which pre-1990 would not have been considered synthetic at all.
"Synthetic blend," meanwhile, can be basically any mix of Group I–II with Group III–V.
So yes — Castrol Edge High Mileage Advanced Full Synthetic made in the U.S. is, you guessed it, Group III. But Castrol Edge Full Synthetic made in Germany (even with the same name) is typically a true Group IV oil.
Given how screwed up the labeling system is, I just stick with Costco.
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I hear what you're saying. He's super honest.
He does mostly dyno testing and in-depth explanations.
He does run an oil testing service, but he never hard-sells it, and he doesn't badmouth other oil testing labs.
.
That all goes back to a famous lawsuit between Mobil and Castrol in the 1990s (yes, that Castrol).
Base oils are traditionally classified into five groups. Groups I, II, and III are derived from conventional crude oil. Groups IV and V are what were originally considered real synthetics — chemically engineered hydrocarbons like PAO, esters, polyglycols, or silicone. Mobil pioneered much of this technology.
For a long time, only Group IV and V oils could legally be labeled "synthetic," and they commanded a premium because they retained their physical properties far better.
In the 1990s, Castrol started using highly processed Group III base oils and marketing them as synthetic. Mobil sued, arguing that Group III was still conventional oil. Mobil lost. Castrol's argument was that Group III oils are so heavily processed that calling them synthetic was justified.
Fast forward to today: in the U.S. (but not in places like Germany or Japan), "synthetic" can legally mean Group III, IV, or V. So "100% synthetic" can be 100% Group III — which pre-1990 would not have been considered synthetic at all.
"Synthetic blend," meanwhile, can be basically any mix of Group I–II with Group III–V.
So yes — Castrol Edge High Mileage Advanced Full Synthetic made in the U.S. is, you guessed it, Group III. But Castrol Edge Full Synthetic made in Germany (even with the same name) is typically a true Group IV oil.
Given how screwed up the labeling system is, I just stick with Costco.
Leave a Comment