Synthetic Motor Oil Mar 4, 2019 Test: Which Brand Wins?
In our Mar 4, 2019 test we compared 2 synthetic motor oil options head to head. Amsoil came out on top. See the measured results, the runner-up, the budget pick, and a link to the full test video.
Amsoil
Price shown in test: $12.85 per quart
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Royal Purple
Price shown in test: $9.78 per quart
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The quick take
The short version of why each pick lands where it does, built straight from the measured results.
“I think Amsoil demonstrated today that it's a really, really good synthetic oil.”
The measured results
Every number below is read straight from the test. Products are listed in the order they finished.
All measurements (3 more)+
Lubricity wear scar
- 1Amsoil Signature Seriesapproximately13%
smaller than Royal Purple's, described as the winner of this test; no absolute measurement given, only the relative percentage
- 2Royal Purpleapproximately13%
larger than Amsoil's; both oils performed impressively overall
Evaporative loss (200g oil, 375-400F for 2hr)
- 1Amsoil Signature Series
before-heating weight 414.76 g; the after-heating weight is never spoken in the transcript (likely shown on screen only), so the actual weight lost cannot be confirmed from narration alone
- 2Royal Purple406.3 g
before heating, 404.17 g after, a loss of about 2.13 g
Cold oil flow at -15F, 24hr freezer soak (4-lane race, new and heat-exposed 'cooked' samples)
- 1Amsoil Signature Series
new Amsoil finished 1st of all 4 lanes, beating cooked Amsoil by less than 1 inch, new Royal Purple by over 3 inches, and cooked Royal Purple by nearly 5 inches; cooked Amsoil finished 2nd, still ahead of new Royal Purple by about 3 inches
- 2Royal Purple
new Royal Purple finished 3rd of 4 lanes (behind new Amsoil by over 3in and cooked Amsoil by about 3in, but ahead of cooked Royal Purple by less than 2in); cooked Royal Purple finished last (4th), beaten by new Amsoil by nearly 5 inches
How it was tested
- lubricity/film strength wear scar test on a bearing tester
- informal evaporative loss test, approximately 200g oil heated to 375-400F for 2 hours (not true ASTM Noack conditions, which call for 482F for 1 hour)
- cold oil flow test at -15F after a 24hr freezer soak, new vs heat-exposed ('cooked') oil samples raced in 4 lanes
“I think Amsoil demonstrated today that it's a really, really good synthetic oil.”
