Both are high-quality full synthetic oils that meet or beat the standards of modern engines. The biggest difference between them shows up at low temperatures.
Amsoil claims better numbers on cold-flow tests. Some drivers report smoother starts and less engine noise after switching to it.
Mobil 1 still performs well in the cold and has its own strengths, including wider availability and a strong reputation in racing.
Mobil 1 Advanced Fuel Economy 0W-20 Motor Oil
What the cold-crank test numbers show
AMSOIL Signature Series 0W-20 Synthetic Motor Oil
The standard test for cold-start performance is the ASTM D5293 Cold-Cranking Simulator test. It measures how thick the oil is at low temperatures, in centipoise (cP). A lower number means the oil flows more easily.
According to figures Amsoil has published, its 0W-20 Hybrid Motor Oil measured 5,476 cP, compared with 6,517 cP for Mobil 1’s 0W-20. That works out to about a 16% difference in Amsoil’s favor.
Amsoil also reports that its Signature Series 5W-30 measured 3,800 mPa·s in cold-crank testing, notably lower than several other premium oils it was compared against.
For diesel, Amsoil says its 0W-40 Max-Duty Diesel Oil delivers four times better cold-temperature performance than a standard 15W-40 oil. These are figures Amsoil itself has published, so treat them as the company’s claims.
Mobil 1 isn’t weak in the cold by any means. Mobil 1’s 0W-40 and similar variants perform far better than conventional (non-synthetic) oils at low temperatures.
Where each oil has an edge
Amsoil Signature Series 5W-30 Synthetic Motor Oil
Amsoil has built its reputation around cold-weather performance. Technical comparisons cited by the company show it holding up with more stability and less resistance at extreme temperatures than Mobil 1.
Amsoil is especially popular in colder regions and “severe service” situations.
Mobil 1 Advanced Full Synthetic 5W-30 Motor Oil
Mobil 1 is a mainstay in racing and performs reliably across a wide range of driving conditions. It’s also easier to find at retail stores, which matters if you need a quick top-off, and it tends to cost less for drivers who stick to standard 5,000 to 10,000 mile oil change intervals.
If you live somewhere with regular sub-zero temperatures, like Vermont or parts of Canada, the lower cold-crank viscosity Amsoil reports could offer a real, measurable advantage.
If your winters are more moderate, either brand should protect your engine well, as long as you use the correct winter viscosity grade (like 0W or 5W) listed in your owner’s manual.
Which oil fits your vehicle
Turbocharged engines: Amsoil Signature Series is aimed at modern turbo engines, like Ford EcoBoost or GM four-cylinders. Amsoil says it protects turbochargers 72% better than the GM dexos1 Gen 2 requirement.
Mobil 1 Extended Performance is also a solid option for turocharged engines for its ability to remain stable at temperature extremes. You can check out some dexos-approved motor oils to see how other lubricants compare to this standard.
Diesel engines: Amsoil claims its Max-Duty Diesel oils performs four times better in cold starts than a standard 15W-40. For heavy hauling in extreme heat, Mobil Delvac Extreme is known for holding up well thermally.
Mobil Delvac 0W-40 Diesel Motor Oil
High-mileage vehicles: Amsoil’s 100% Synthetic High-Mileage Motor Oil is tested, according to the company, to cut sludge by 67% in older engines. Mobil 1 Extended Performance is also formulated for high-mileage engines and helps keep them clean.
Hybrid vehicles: Both brands make 0W-20 oils designed for the stop-start driving pattern of hybrids, where the engine frequently shuts off and restarts, so the oil often runs cooler than in a standard engine.
If you are shopping for this viscosity, you can look up popular 0W-20 motor oil brands currently on the market.
Mobil 1 Truck & SUV 0W-20 Full Synthetic Motor Oil
Customer review for Amsoil and Mobil 1
These takeaways come from owner comments on forums and product review pages, not lab testing. Treat them as a sense of general opinion rather than verified fact.
Real-world reviews and owner reports lean toward Amsoil for extreme cold, mostly because of quieter cold starts and less laboring at startup. Most owners of both brands are satisfied overall, but specific mechanical improvements come up more often in reviews of Amsoil in sub-zero conditions. Keep in mind these are individual experiences, not controlled tests.
What Amsoil customers report in winter
Several Toyota Tundra owners described a timing chain rattle or hydraulic lifter noise during cold starts on Mobil 1, which they said went away after switching to Amsoil.
Owners in extreme climates like Vermont and Alaska say Amsoil helps their engines “turn over cleanly” in sub-zero weather, while other oils leave the engine laboring before oil pressure builds.
One vehicle owner running 20 different motors on a farm, including an L5P diesel and a 5.3L engine, said none of them tick and the lifters stay silent on Amsoil, even after long idle periods in extreme cold.
If you drive a similar truck, you may want to find out the Chevy 5.3 oil capacity and oil type specifications before planning your next service.
What Mobil 1 customers report in winter
Some Pacific Northwest drivers report running Mobil 1 0W-40 year-round for decades without issues. Many customers say they’re satisfied with its performance and reliability, and its wide availability at retail stores is a common reason people mention for sticking with it
Across both brands, users consistently say that a 0W winter weight, such as 0W-20, 0W-30, or 0W-40, makes a noticeably easier startup than conventional or higher-viscosity oil in a bad winter.
Owners who make a lot of short winter trips are also advised to change their oil more often, no matter the brand, since those short drives may not get the engine hot enough to burn off moisture and fuel that end up in the oil.
Closing Notes
Amsoil tends to win on technical cold-start numbers, and Mobil 1 tends to win on practical, everyday factors.
Amsoil’s lower cold-crank viscosity means faster flow during that critical first 30 seconds of startup, and owner reports back that up with fewer rattles and cleaner cold starts, especially in extreme climates. Its diesel oil also claims a big edge in cold-temperature performance over standard 15W-40 oil.
Mobil 1 holds its own where it counts day to day. It carries official manufacturer certifications, like Acura’s HTO-06 or BMW LL-01, that some Amsoil products only claim to meet without the same formal testing.
Mobil 1 is also easier to find in a pinch, tends to cost less in bulk, and is the factory-fill choice for vehicles like Porsche and the Nissan GT-R.
Choose Amsoil if you want the strongest cold-weather performance and are willing to pay for it. Choose Mobil 1 if you want a trusted synthetic that’s easy to find, budget-friendly, and keeps your warranty on solid ground.
